llvosky.cpp

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#include "llviewerprecompiledheaders.h"

#include "llvosky.h"

#include "imageids.h"
#include "llfeaturemanager.h"
#include "llviewercontrol.h"
#include "llframetimer.h"
#include "timing.h"

#include "llagent.h"
#include "lldrawable.h"
#include "llface.h"
#include "llcubemap.h"
#include "lldrawpoolsky.h"
#include "lldrawpoolwater.h"
#include "llglheaders.h"
#include "llsky.h"
#include "llviewercamera.h"
#include "llviewerimagelist.h"
#include "llviewerobjectlist.h"
#include "llviewerregion.h"
#include "llworld.h"
#include "pipeline.h"
#include "lldrawpoolwlsky.h"
#include "llwlparammanager.h"
#include "llwaterparammanager.h"

#undef min
#undef max

static const S32 NUM_TILES_X = 8;
static const S32 NUM_TILES_Y = 4;
static const S32 NUM_TILES = NUM_TILES_X * NUM_TILES_Y;

// Heavenly body constants
static const F32 SUN_DISK_RADIUS        = 0.5f;
static const F32 MOON_DISK_RADIUS       = SUN_DISK_RADIUS * 0.9f;
static const F32 SUN_INTENSITY = 1e5;
static const F32 SUN_DISK_INTENSITY = 24.f;


// Texture coordinates:
static const LLVector2 TEX00 = LLVector2(0.f, 0.f);
static const LLVector2 TEX01 = LLVector2(0.f, 1.f);
static const LLVector2 TEX10 = LLVector2(1.f, 0.f);
static const LLVector2 TEX11 = LLVector2(1.f, 1.f);

// Exported globals
LLUUID gSunTextureID = IMG_SUN;
LLUUID gMoonTextureID = IMG_MOON;

//static 
LLColor3 LLHaze::sAirScaSeaLevel;

class LLFastLn
{
public:
        LLFastLn() 
        {
                mTable[0] = 0;
                for( S32 i = 1; i < 257; i++ )
                {
                        mTable[i] = log((F32)i);
                }
        }

        F32 ln( F32 x )
        {
                const F32 OO_255 = 0.003921568627450980392156862745098f;
                const F32 LN_255 = 5.5412635451584261462455391880218f;

                if( x < OO_255 )
                {
                        return log(x);
                }
                else
                if( x < 1 )
                {
                        x *= 255.f;
                        S32 index = llfloor(x);
                        F32 t = x - index;
                        F32 low = mTable[index];
                        F32 high = mTable[index + 1];
                        return low + t * (high - low) - LN_255;
                }
                else
                if( x <= 255 )
                {
                        S32 index = llfloor(x);
                        F32 t = x - index;
                        F32 low = mTable[index];
                        F32 high = mTable[index + 1];
                        return low + t * (high - low);
                }
                else
                {
                        return log( x );
                }
        }

        F32 pow( F32 x, F32 y )
        {
                return (F32)LL_FAST_EXP(y * ln(x));
        }


private:
        F32 mTable[257]; // index 0 is unused
};

static LLFastLn gFastLn;


// Functions used a lot.

inline F32 LLHaze::calcPhase(const F32 cos_theta) const
{
        const F32 g2 = mG * mG;
        const F32 den = 1 + g2 - 2 * mG * cos_theta;
        return (1 - g2) * gFastLn.pow(den, -1.5);
}

inline void color_pow(LLColor3 &col, const F32 e)
{
        col.mV[0] = gFastLn.pow(col.mV[0], e);
        col.mV[1] = gFastLn.pow(col.mV[1], e);
        col.mV[2] = gFastLn.pow(col.mV[2], e);
}

inline LLColor3 color_norm(const LLColor3 &col)
{
        const F32 m = color_max(col);
        if (m > 1.f)
        {
                return 1.f/m * col;
        }
        else return col;
}

inline void color_gamma_correct(LLColor3 &col)
{
        const F32 gamma_inv = 1.f/1.2f;
        if (col.mV[0] != 0.f)
        {
                col.mV[0] = gFastLn.pow(col.mV[0], gamma_inv);
        }
        if (col.mV[1] != 0.f)
        {
                col.mV[1] = gFastLn.pow(col.mV[1], gamma_inv);
        }
        if (col.mV[2] != 0.f)
        {
                col.mV[2] = gFastLn.pow(col.mV[2], gamma_inv);
        }
}



/***************************************
                SkyTex
***************************************/

S32 LLSkyTex::sComponents = 4;
S32 LLSkyTex::sResolution = 64;
F32 LLSkyTex::sInterpVal = 0.f;
S32 LLSkyTex::sCurrent = 0;


LLSkyTex::LLSkyTex() :
        mSkyData(NULL),
        mSkyDirs(NULL)
{
}

void LLSkyTex::init()
{
        mSkyData = new LLColor4[sResolution * sResolution];
        mSkyDirs = new LLVector3[sResolution * sResolution];

        for (S32 i = 0; i < 2; ++i)
        {
                mImageGL[i] = new LLImageGL(FALSE);
                mImageGL[i]->setClamp(TRUE, TRUE);
                mImageRaw[i] = new LLImageRaw(sResolution, sResolution, sComponents);
                
                initEmpty(i);
        }
}

void LLSkyTex::cleanupGL()
{
        mImageGL[0] = NULL;
        mImageGL[1] = NULL;
}

void LLSkyTex::restoreGL()
{
        for (S32 i = 0; i < 2; i++)
        {
                mImageGL[i] = new LLImageGL(FALSE);
                mImageGL[i]->setClamp(TRUE, TRUE);
        }
}

LLSkyTex::~LLSkyTex()
{
        delete[] mSkyData;
        mSkyData = NULL;

        delete[] mSkyDirs;
        mSkyDirs = NULL;
}


void LLSkyTex::initEmpty(const S32 tex)
{
        U8* data = mImageRaw[tex]->getData();
        for (S32 i = 0; i < sResolution; ++i)
        {
                for (S32 j = 0; j < sResolution; ++j)
                {
                        const S32 basic_offset = (i * sResolution + j);
                        S32 offset = basic_offset * sComponents;
                        data[offset] = 0;
                        data[offset+1] = 0;
                        data[offset+2] = 0;
                        data[offset+3] = 255;

                        mSkyData[basic_offset].setToBlack();
                }
        }

        createGLImage(tex);
}

void LLSkyTex::create(const F32 brightness)
{
        U8* data = mImageRaw[sCurrent]->getData();
        for (S32 i = 0; i < sResolution; ++i)
        {
                for (S32 j = 0; j < sResolution; ++j)
                {
                        const S32 basic_offset = (i * sResolution + j);
                        S32 offset = basic_offset * sComponents;
                        U32* pix = (U32*)(data + offset);
                        LLColor4U temp = LLColor4U(mSkyData[basic_offset]);
                        *pix = temp.mAll;
                }
        }
        createGLImage(sCurrent);
}




void LLSkyTex::createGLImage(S32 which)
{       
        mImageGL[which]->createGLTexture(0, mImageRaw[which]);
        mImageGL[which]->setClamp(TRUE, TRUE);
}

void LLSkyTex::bindTexture(BOOL curr)
{
        mImageGL[getWhich(curr)]->bind();
}

/***************************************
                Sky
***************************************/

F32     LLHeavenBody::sInterpVal = 0;

S32 LLVOSky::sResolution = LLSkyTex::getResolution();
S32 LLVOSky::sTileResX = sResolution/NUM_TILES_X;
S32 LLVOSky::sTileResY = sResolution/NUM_TILES_Y;

LLVOSky::LLVOSky(const LLUUID &id, const LLPCode pcode, LLViewerRegion *regionp)
:       LLStaticViewerObject(id, pcode, regionp),
        mSun(SUN_DISK_RADIUS), mMoon(MOON_DISK_RADIUS),
        mBrightnessScale(1.f),
        mBrightnessScaleNew(0.f),
        mBrightnessScaleGuess(1.f),
        mWeatherChange(FALSE),
        mCloudDensity(0.2f),
        mWind(0.f),
        mForceUpdate(FALSE),
        mWorldScale(1.f),
        mBumpSunDir(0.f, 0.f, 1.f)
{
        bool error = false;
        
        dome_radius = 1.f;
        dome_offset_ratio = 0.f;
        sunlight_color = LLColor3();
        ambient = LLColor3();
        gamma = 1.f;
        lightnorm = LLVector4();
        blue_density = LLColor3();
        blue_horizon = LLColor3();
        haze_density = 0.f;
        haze_horizon = LLColor3();
        density_multiplier = 0.f;
        max_y = 0.f;
        glow = LLColor3();
        cloud_shadow = 0.f;
        cloud_color = LLColor3();
        cloud_scale = 0.f;
        cloud_pos_density1 = LLColor3();
        cloud_pos_density2 = LLColor3();


        mInitialized = FALSE;
        mbCanSelect = FALSE;
        mUpdateTimer.reset();

        for (S32 i = 0; i < 6; i++)
        {
                mSkyTex[i].init();
                mShinyTex[i].init();
        }
        for (S32 i=0; i<FACE_COUNT; i++)
        {
                mFace[i] = NULL;
        }
        
        mCameraPosAgent = gAgent.getCameraPositionAgent();
        mAtmHeight = ATM_HEIGHT;
        mEarthCenter = LLVector3(mCameraPosAgent.mV[0], mCameraPosAgent.mV[1], -EARTH_RADIUS);

        mSunDefaultPosition = LLVector3(LLWLParamManager::instance()->mCurParams.getVector("lightnorm", error));
        if (gSavedSettings.getBOOL("SkyOverrideSimSunPosition"))
        {
                initSunDirection(mSunDefaultPosition, LLVector3(0, 0, 0));
        }
        mAmbientScale = gSavedSettings.getF32("SkyAmbientScale");
        mNightColorShift = gSavedSettings.getColor3("SkyNightColorShift");
        mFogColor.mV[VRED] = mFogColor.mV[VGREEN] = mFogColor.mV[VBLUE] = 0.5f;
        mFogColor.mV[VALPHA] = 0.0f;
        mFogRatio = 1.2f;

        mSun.setIntensity(SUN_INTENSITY);
        mMoon.setIntensity(0.1f * SUN_INTENSITY);

        mSunTexturep = gImageList.getImage(gSunTextureID, TRUE, TRUE);
        mSunTexturep->setClamp(TRUE, TRUE);
        mMoonTexturep = gImageList.getImage(gMoonTextureID, TRUE, TRUE);
        mMoonTexturep->setClamp(TRUE, TRUE);
        mBloomTexturep = gImageList.getImage(IMG_BLOOM1);
        mBloomTexturep->setClamp(TRUE, TRUE);

        mHeavenlyBodyUpdated = FALSE ;
}


LLVOSky::~LLVOSky()
{
        // Don't delete images - it'll get deleted by gImageList on shutdown
        // This needs to be done for each texture

        mCubeMap = NULL;
}

void LLVOSky::initClass()
{
        LLHaze::initClass();
}


void LLVOSky::init()
{
        const F32 haze_int = color_intens(mHaze.calcSigSca(0));
        mHazeConcentration = haze_int /
                (color_intens(LLHaze::calcAirSca(0)) + haze_int);

        calcAtmospherics();

        // Initialize the cached normalized direction vectors
        for (S32 side = 0; side < 6; ++side)
        {
                for (S32 tile = 0; tile < NUM_TILES; ++tile)
                {
                        initSkyTextureDirs(side, tile);
                        createSkyTexture(side, tile);
                }
        }

        for (S32 i = 0; i < 6; ++i)
        {
                mSkyTex[i].create(1.0f);
                mShinyTex[i].create(1.0f);
        }

        initCubeMap();
        mInitialized = true;

        mHeavenlyBodyUpdated = FALSE ;
}

void LLVOSky::initCubeMap() 
{
        std::vector<LLPointer<LLImageRaw> > images;
        for (S32 side = 0; side < 6; side++)
        {
                images.push_back(mShinyTex[side].getImageRaw());
        }
        if (mCubeMap)
        {
                mCubeMap->init(images);
        }
        else if (gSavedSettings.getBOOL("RenderWater") && gGLManager.mHasCubeMap && LLFeatureManager::getInstance()->isFeatureAvailable("RenderCubeMap"))
        {
                mCubeMap = new LLCubeMap();
                mCubeMap->init(images);
        }
}


void LLVOSky::cleanupGL()
{
        S32 i;
        for (i = 0; i < 6; i++)
        {
                mSkyTex[i].cleanupGL();
        }
        if (getCubeMap())
        {
                getCubeMap()->destroyGL();
        }
}

void LLVOSky::restoreGL()
{
        S32 i;
        for (i = 0; i < 6; i++)
        {
                mSkyTex[i].restoreGL();
        }
        mSunTexturep = gImageList.getImage(gSunTextureID, TRUE, TRUE);
        mSunTexturep->setClamp(TRUE, TRUE);
        mMoonTexturep = gImageList.getImage(gMoonTextureID, TRUE, TRUE);
        mMoonTexturep->setClamp(TRUE, TRUE);
        mBloomTexturep = gImageList.getImage(IMG_BLOOM1);
        mBloomTexturep->setClamp(TRUE, TRUE);

        calcAtmospherics();     

        if (gSavedSettings.getBOOL("RenderWater") && gGLManager.mHasCubeMap
            && LLFeatureManager::getInstance()->isFeatureAvailable("RenderCubeMap"))
        {
                LLCubeMap* cube_map = getCubeMap();

                std::vector<LLPointer<LLImageRaw> > images;
                for (S32 side = 0; side < 6; side++)
                {
                        images.push_back(mShinyTex[side].getImageRaw());
                }

                if(cube_map)
                {
                        cube_map->init(images);
                        mForceUpdate = TRUE;
                }
        }

        if (mDrawable)
        {
                gPipeline.markRebuild(mDrawable, LLDrawable::REBUILD_VOLUME, TRUE);
        }

}

void LLVOSky::initSkyTextureDirs(const S32 side, const S32 tile)
{
        S32 tile_x = tile % NUM_TILES_X;
        S32 tile_y = tile / NUM_TILES_X;

        S32 tile_x_pos = tile_x * sTileResX;
        S32 tile_y_pos = tile_y * sTileResY;

        F32 coeff[3] = {0, 0, 0};
        const S32 curr_coef = side >> 1; // 0/1 = Z axis, 2/3 = Y, 4/5 = X
        const S32 side_dir = (((side & 1) << 1) - 1);  // even = -1, odd = 1
        const S32 x_coef = (curr_coef + 1) % 3;
        const S32 y_coef = (x_coef + 1) % 3;

        coeff[curr_coef] = (F32)side_dir;

        F32 inv_res = 1.f/sResolution;
        S32 x, y;
        for (y = tile_y_pos; y < (tile_y_pos + sTileResY); ++y)
        {
                for (x = tile_x_pos; x < (tile_x_pos + sTileResX); ++x)
                {
                        coeff[x_coef] = F32((x<<1) + 1) * inv_res - 1.f;
                        coeff[y_coef] = F32((y<<1) + 1) * inv_res - 1.f;
                        LLVector3 dir(coeff[0], coeff[1], coeff[2]);
                        dir.normVec();
                        mSkyTex[side].setDir(dir, x, y);
                        mShinyTex[side].setDir(dir, x, y);
                }
        }
}

void LLVOSky::createSkyTexture(const S32 side, const S32 tile)
{
        S32 tile_x = tile % NUM_TILES_X;
        S32 tile_y = tile / NUM_TILES_X;

        S32 tile_x_pos = tile_x * sTileResX;
        S32 tile_y_pos = tile_y * sTileResY;

        S32 x, y;
        for (y = tile_y_pos; y < (tile_y_pos + sTileResY); ++y)
        {
                for (x = tile_x_pos; x < (tile_x_pos + sTileResX); ++x)
                {
                        mSkyTex[side].setPixel(calcSkyColorInDir(mSkyTex[side].getDir(x, y)), x, y);
                        mShinyTex[side].setPixel(calcSkyColorInDir(mSkyTex[side].getDir(x, y), true), x, y);
                }
        }
}

static inline LLColor3 componentDiv(LLColor3 const &left, LLColor3 const & right)
{
        return LLColor3(left.mV[0]/right.mV[0],
                                         left.mV[1]/right.mV[1],
                                         left.mV[2]/right.mV[2]);
}


static inline LLColor3 componentMult(LLColor3 const &left, LLColor3 const & right)
{
        return LLColor3(left.mV[0]*right.mV[0],
                                         left.mV[1]*right.mV[1],
                                         left.mV[2]*right.mV[2]);
}


static inline LLColor3 componentExp(LLColor3 const &v)
{
        return LLColor3(exp(v.mV[0]),
                                         exp(v.mV[1]),
                                         exp(v.mV[2]));
}

static inline LLColor3 componentPow(LLColor3 const &v, F32 exponent)
{
        return LLColor3(pow(v.mV[0], exponent),
                                        pow(v.mV[1], exponent),
                                        pow(v.mV[2], exponent));
}

static inline LLColor3 componentSaturate(LLColor3 const &v)
{
        return LLColor3(std::max(std::min(v.mV[0], 1.f), 0.f),
                                         std::max(std::min(v.mV[1], 1.f), 0.f),
                                         std::max(std::min(v.mV[2], 1.f), 0.f));
}


static inline LLColor3 componentSqrt(LLColor3 const &v)
{
        return LLColor3(sqrt(v.mV[0]),
                                         sqrt(v.mV[1]),
                                         sqrt(v.mV[2]));
}

static inline void componentMultBy(LLColor3 & left, LLColor3 const & right)
{
        left.mV[0] *= right.mV[0];
        left.mV[1] *= right.mV[1];
        left.mV[2] *= right.mV[2];
}

static inline LLColor3 colorMix(LLColor3 const & left, LLColor3 const & right, F32 amount)
{
        return (left + ((right - left) * amount));
}

static inline F32 texture2D(LLPointer<LLImageRaw> const & tex, LLVector2 const & uv)
{
        U16 w = tex->getWidth();
        U16 h = tex->getHeight();

        U16 r = U16(uv[0] * w) % w;
        U16 c = U16(uv[1] * h) % h;

        U8 const * imageBuffer = tex->getData();

        U8 sample = imageBuffer[r * w + c];

        return sample / 255.f;
}

static inline LLColor3 smear(F32 val)
{
        return LLColor3(val, val, val);
}

void LLVOSky::initAtmospherics(void)
{       
        bool error;
        
        // uniform parameters for convenience
        dome_radius = LLWLParamManager::instance()->getDomeRadius();
        dome_offset_ratio = LLWLParamManager::instance()->getDomeOffset();
        sunlight_color = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("sunlight_color", error));
        ambient = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("ambient", error));
        //lightnorm = LLWLParamManager::instance()->mCurParams.getVector("lightnorm", error);
        gamma = LLWLParamManager::instance()->mCurParams.getVector("gamma", error)[0];
        blue_density = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("blue_density", error));
        blue_horizon = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("blue_horizon", error));
        haze_density = LLWLParamManager::instance()->mCurParams.getVector("haze_density", error)[0];
        haze_horizon = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("haze_horizon", error));
        density_multiplier = LLWLParamManager::instance()->mCurParams.getVector("density_multiplier", error)[0];
        max_y = LLWLParamManager::instance()->mCurParams.getVector("max_y", error)[0];
        glow = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("glow", error));
        cloud_shadow = LLWLParamManager::instance()->mCurParams.getVector("cloud_shadow", error)[0];
        cloud_color = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("cloud_color", error));
        cloud_scale = LLWLParamManager::instance()->mCurParams.getVector("cloud_scale", error)[0];
        cloud_pos_density1 = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("cloud_pos_density1", error));
        cloud_pos_density2 = LLColor3(LLWLParamManager::instance()->mCurParams.getVector("cloud_pos_density2", error));

        // light norm is different.  We need the sun's direction, not the light direction
        // which could be from the moon.  And we need to clamp it
        // just like for the gpu
        LLVector3 sunDir = gSky.getSunDirection();

        // CFR_TO_OGL
        lightnorm = LLVector4(sunDir.mV[1], sunDir.mV[2], sunDir.mV[0], 0);
        unclamped_lightnorm = lightnorm;
        if(lightnorm.mV[1] < -0.1f)
        {
                lightnorm.mV[1] = -0.1f;
        }
        
}

LLColor4 LLVOSky::calcSkyColorInDir(const LLVector3 &dir, bool isShiny)
{
        F32 saturation = 0.3f;
        if (dir.mV[VZ] < -0.02f)
        {
                LLColor4 col = LLColor4(llmax(mFogColor[0],0.2f), llmax(mFogColor[1],0.2f), llmax(mFogColor[2],0.22f),0.f);
                if (isShiny)
                {
                        LLColor3 desat_fog = LLColor3(mFogColor);
                        F32 brightness = desat_fog.brightness();
                        // So that shiny somewhat shows up at night.
                        if (brightness < 0.15f)
                        {
                                brightness = 0.15f;
                                desat_fog = smear(0.15f);
                        }
                        LLColor3 greyscale = smear(brightness);
                        desat_fog = desat_fog * saturation + greyscale * (1.0f - saturation);
                        if (!gPipeline.canUseWindLightShaders())
                        {
                                col = LLColor4(desat_fog, 0.f);
                        }
                        else 
                        {
                                col = LLColor4(desat_fog * 0.5f, 0.f);
                        }
                }
                float x = 1.0f-fabsf(-0.1f-dir.mV[VZ]);
                x *= x;
                col.mV[0] *= x*x;
                col.mV[1] *= powf(x, 2.5f);
                col.mV[2] *= x*x*x;
                return col;
        }

        // undo OGL_TO_CFR_ROTATION and negate vertical direction.
        LLVector3 Pn = LLVector3(-dir[1] , -dir[2], -dir[0]);

        LLColor3 vary_HazeColor(0,0,0);
        LLColor3 vary_CloudColorSun(0,0,0);
        LLColor3 vary_CloudColorAmbient(0,0,0);
        F32 vary_CloudDensity(0);
        LLVector2 vary_HorizontalProjection[2];
        vary_HorizontalProjection[0] = LLVector2(0,0);
        vary_HorizontalProjection[1] = LLVector2(0,0);

        calcSkyColorWLVert(Pn, vary_HazeColor, vary_CloudColorSun, vary_CloudColorAmbient,
                                                vary_CloudDensity, vary_HorizontalProjection);
        
        LLColor3 sky_color =  calcSkyColorWLFrag(Pn, vary_HazeColor, vary_CloudColorSun, vary_CloudColorAmbient, 
                                                                vary_CloudDensity, vary_HorizontalProjection);
        if (isShiny)
        {
                F32 brightness = sky_color.brightness();
                LLColor3 greyscale = smear(brightness);
                sky_color = sky_color * saturation + greyscale * (1.0f - saturation);
                sky_color *= (0.5f + 0.5f * brightness);
        }
        return LLColor4(sky_color, 0.0f);
}

// turn on floating point precision
// in vs2003 for this function.  Otherwise
// sky is aliased looking 7:10 - 8:50
#if LL_MSVC && __MSVC_VER__ < 8
#pragma optimize("p", on)
#endif

void LLVOSky::calcSkyColorWLVert(LLVector3 & Pn, LLColor3 & vary_HazeColor, LLColor3 & vary_CloudColorSun, 
                                                        LLColor3 & vary_CloudColorAmbient, F32 & vary_CloudDensity, 
                                                        LLVector2 vary_HorizontalProjection[2])
{
        // project the direction ray onto the sky dome.
        F32 phi = acos(Pn[1]);
        F32 sinA = sin(F_PI - phi);
        F32 Plen = dome_radius * sin(F_PI + phi + asin(dome_offset_ratio * sinA)) / sinA;

        Pn *= Plen;

        vary_HorizontalProjection[0] = LLVector2(Pn[0], Pn[2]);
        vary_HorizontalProjection[0] /= - 2.f * Plen;

        // Set altitude
        if (Pn[1] > 0.f)
        {
                Pn *= (max_y / Pn[1]);
        }
        else
        {
                Pn *= (-32000.f / Pn[1]);
        }

        Plen = Pn.magVec();
        Pn /= Plen;

        // Initialize temp variables
        LLColor3 sunlight = sunlight_color;

        // Sunlight attenuation effect (hue and brightness) due to atmosphere
        // this is used later for sunlight modulation at various altitudes
        LLColor3 light_atten =
                (blue_density * 1.0 + smear(haze_density * 0.25f)) * (density_multiplier * max_y);

        // Calculate relative weights
        LLColor3 temp2(0.f, 0.f, 0.f);
        LLColor3 temp1 = blue_density + smear(haze_density);
        LLColor3 blue_weight = componentDiv(blue_density, temp1);
        LLColor3 haze_weight = componentDiv(smear(haze_density), temp1);

        // Compute sunlight from P & lightnorm (for long rays like sky)
        temp2.mV[1] = llmax(F_APPROXIMATELY_ZERO, llmax(0.f, Pn[1]) * 1.0f + lightnorm[1] );

        temp2.mV[1] = 1.f / temp2.mV[1];
        componentMultBy(sunlight, componentExp((light_atten * -1.f) * temp2.mV[1]));

        // Distance
        temp2.mV[2] = Plen * density_multiplier;

        // Transparency (-> temp1)
        temp1 = componentExp((temp1 * -1.f) * temp2.mV[2]);


        // Compute haze glow
        temp2.mV[0] = Pn * LLVector3(lightnorm);

        temp2.mV[0] = 1.f - temp2.mV[0];
                // temp2.x is 0 at the sun and increases away from sun
        temp2.mV[0] = llmax(temp2.mV[0], .001f);        
                // Set a minimum "angle" (smaller glow.y allows tighter, brighter hotspot)
        temp2.mV[0] *= glow.mV[0];
                // Higher glow.x gives dimmer glow (because next step is 1 / "angle")
        temp2.mV[0] = pow(temp2.mV[0], glow.mV[2]);
                // glow.z should be negative, so we're doing a sort of (1 / "angle") function

        // Add "minimum anti-solar illumination"
        temp2.mV[0] += .25f;


        // Haze color above cloud
        vary_HazeColor = (blue_horizon * blue_weight * (sunlight + ambient)
                                + componentMult(haze_horizon.mV[0] * haze_weight, sunlight * temp2.mV[0] + ambient)
                         );     

        // Increase ambient when there are more clouds
        LLColor3 tmpAmbient = ambient + (LLColor3::white - ambient) * cloud_shadow * 0.5f;

        // Dim sunlight by cloud shadow percentage
        sunlight *= (1.f - cloud_shadow);

        // Haze color below cloud
        LLColor3 additiveColorBelowCloud = (blue_horizon * blue_weight * (sunlight + tmpAmbient)
                                + componentMult(haze_horizon.mV[0] * haze_weight, sunlight * temp2.mV[0] + tmpAmbient)
                         );     

        // Final atmosphere additive
        componentMultBy(vary_HazeColor, LLColor3::white - temp1);

        sunlight = sunlight_color;
        temp2.mV[1] = llmax(0.f, lightnorm[1] * 2.f);
        temp2.mV[1] = 1.f / temp2.mV[1];
        componentMultBy(sunlight, componentExp((light_atten * -1.f) * temp2.mV[1]));

        // Attenuate cloud color by atmosphere
        temp1 = componentSqrt(temp1);   //less atmos opacity (more transparency) below clouds

        // At horizon, blend high altitude sky color towards the darker color below the clouds
        vary_HazeColor +=
                componentMult(additiveColorBelowCloud - vary_HazeColor, LLColor3::white - componentSqrt(temp1));
                
        if (Pn[1] < 0.f)
        {
                // Eric's original: 
                // LLColor3 dark_brown(0.143f, 0.129f, 0.114f);
                LLColor3 dark_brown(0.082f, 0.076f, 0.066f);
                LLColor3 brown(0.430f, 0.386f, 0.322f);
                LLColor3 sky_lighting = sunlight + ambient;
                F32 haze_brightness = vary_HazeColor.brightness();

                if (Pn[1] < -0.05f)
                {
                        vary_HazeColor = colorMix(dark_brown, brown, -Pn[1] * 0.9f) * sky_lighting * haze_brightness;
                }
                
                if (Pn[1] > -0.1f)
                {
                        vary_HazeColor = colorMix(LLColor3::white * haze_brightness, vary_HazeColor, fabs((Pn[1] + 0.05f) * -20.f));
                }
        }
}

#if LL_MSVC && __MSVC_VER__ < 8
#pragma optimize("p", off)
#endif

LLColor3 LLVOSky::calcSkyColorWLFrag(LLVector3 & Pn, LLColor3 & vary_HazeColor, LLColor3 & vary_CloudColorSun, 
                                                        LLColor3 & vary_CloudColorAmbient, F32 & vary_CloudDensity, 
                                                        LLVector2 vary_HorizontalProjection[2])
{
        LLColor3 res;

        LLColor3 color0 = vary_HazeColor;
        
        if (!gPipeline.canUseWindLightShaders())
        {
                LLColor3 color1 = color0 * 2.0f;
                color1 = smear(1.f) - componentSaturate(color1);
                componentPow(color1, gamma);
                res = smear(1.f) - color1;
        } 
        else 
        {
                res = color0;
        }

#       ifndef LL_RELEASE_FOR_DOWNLOAD

        LLColor3 color2 = 2.f * color0;

        LLColor3 color3 = LLColor3(1.f, 1.f, 1.f) - componentSaturate(color2);
        componentPow(color3, gamma);
        color3 = LLColor3(1.f, 1.f, 1.f) - color3;

        static enum {
                OUT_DEFAULT             = 0,
                OUT_SKY_BLUE    = 1,
                OUT_RED                 = 2,
                OUT_PN                  = 3,
                OUT_HAZE                = 4,
        } debugOut = OUT_DEFAULT;

        switch(debugOut) 
        {
                case OUT_DEFAULT:
                        break;
                case OUT_SKY_BLUE:
                        res = LLColor3(0.4f, 0.4f, 0.9f);
                        break;
                case OUT_RED:
                        res = LLColor3(1.f, 0.f, 0.f);
                        break;
                case OUT_PN:
                        res = LLColor3(Pn[0], Pn[1], Pn[2]);
                        break;
                case OUT_HAZE:
                        res = vary_HazeColor;
                        break;
        }
#       endif // LL_RELEASE_FOR_DOWNLOAD
        return res;
}

LLColor3 LLVOSky::createDiffuseFromWL(LLColor3 diffuse, LLColor3 ambient, LLColor3 sundiffuse, LLColor3 sunambient)
{
        return componentMult(diffuse, sundiffuse) * 4.0f +
                        componentMult(ambient, sundiffuse) * 2.0f + sunambient;
}

LLColor3 LLVOSky::createAmbientFromWL(LLColor3 ambient, LLColor3 sundiffuse, LLColor3 sunambient)
{
        return (componentMult(ambient, sundiffuse) + sunambient) * 0.8f;
}


void LLVOSky::calcAtmospherics(void)
{
        initAtmospherics();

        LLColor3 vary_HazeColor;
        LLColor3 vary_SunlightColor;
        LLColor3 vary_AmbientColor;
        {
                // Initialize temp variables
                LLColor3 sunlight = sunlight_color;

                // Sunlight attenuation effect (hue and brightness) due to atmosphere
                // this is used later for sunlight modulation at various altitudes
                LLColor3 light_atten =
                        (blue_density * 1.0 + smear(haze_density * 0.25f)) * (density_multiplier * max_y);

                // Calculate relative weights
                LLColor3 temp2(0.f, 0.f, 0.f);
                LLColor3 temp1 = blue_density + smear(haze_density);
                LLColor3 blue_weight = componentDiv(blue_density, temp1);
                LLColor3 haze_weight = componentDiv(smear(haze_density), temp1);

                // Compute sunlight from P & lightnorm (for long rays like sky)
                // temp2[1] = llmax(0.f, llmax(0.f, Pn[1]) * 1.0f + lightnorm[1] );
                
                // and vary_sunlight will work properly with moon light
                F32 lighty = unclamped_lightnorm[1];
                if(lighty < NIGHTTIME_ELEVATION_COS)
                {
                        lighty = -lighty;
                }

                temp2.mV[1] = llmax(0.f, lighty);
                temp2.mV[1] = 1.f / temp2.mV[1];
                componentMultBy(sunlight, componentExp((light_atten * -1.f) * temp2.mV[1]));

                // Distance
                temp2.mV[2] = density_multiplier;

                // Transparency (-> temp1)
                temp1 = componentExp((temp1 * -1.f) * temp2.mV[2]);

                // vary_AtmosAttenuation = temp1; 

                //increase ambient when there are more clouds
                LLColor3 tmpAmbient = ambient + (smear(1.f) - ambient) * cloud_shadow * 0.5f;

                //haze color
                vary_HazeColor =
                        (blue_horizon * blue_weight * (sunlight*(1.f - cloud_shadow) + tmpAmbient)      
                        + componentMult(haze_horizon.mV[0] * haze_weight, sunlight*(1.f - cloud_shadow) * temp2.mV[0] + tmpAmbient)
                                 );     

                //brightness of surface both sunlight and ambient
                vary_SunlightColor = componentMult(sunlight, temp1) * 1.f;
                vary_SunlightColor.clamp();
                vary_SunlightColor = smear(1.0f) - vary_SunlightColor;
                vary_SunlightColor = componentPow(vary_SunlightColor, gamma);
                vary_SunlightColor = smear(1.0f) - vary_SunlightColor;
                vary_AmbientColor = componentMult(tmpAmbient, temp1) * 0.5;
                vary_AmbientColor.clamp();
                vary_AmbientColor = smear(1.0f) - vary_AmbientColor;
                vary_AmbientColor = componentPow(vary_AmbientColor, gamma);
                vary_AmbientColor = smear(1.0f) - vary_AmbientColor;

                componentMultBy(vary_HazeColor, LLColor3(1.f, 1.f, 1.f) - temp1);

        }

        mSun.setColor(vary_SunlightColor);
        mMoon.setColor(LLColor3(1.0f, 1.0f, 1.0f));

        mSun.renewDirection();
        mSun.renewColor();
        mMoon.renewDirection();
        mMoon.renewColor();

        float dp = getToSunLast() * LLVector3(0,0,1.f);
        if (dp < 0)
        {
                dp = 0;
        }

        // Since WL scales everything by 2, there should always be at least a 2:1 brightness ratio
        // between sunlight and point lights in windlight to normalize point lights.
        F32 sun_dynamic_range = llmax(gSavedSettings.getF32("RenderSunDynamicRange"), 0.0001f);
        LLWLParamManager::instance()->mSceneLightStrength = 2.0f * (1.0f + sun_dynamic_range * dp);

        mSunDiffuse = vary_SunlightColor;
        mSunAmbient = vary_AmbientColor;
        mMoonDiffuse = vary_SunlightColor;
        mMoonAmbient = vary_AmbientColor;

        mTotalAmbient = vary_AmbientColor;
        mTotalAmbient.setAlpha(1);
        
        mFadeColor = mTotalAmbient + (mSunDiffuse + mMoonDiffuse) * 0.5f;
        mFadeColor.setAlpha(0);
}

BOOL LLVOSky::idleUpdate(LLAgent &agent, LLWorld &world, const F64 &time)
{
        return TRUE;
}

BOOL LLVOSky::updateSky()
{
        if (mDead || !(gPipeline.hasRenderType(LLPipeline::RENDER_TYPE_SKY)))
        {
                return TRUE;
        }
        
        if (mDead)
        {
                // It's dead.  Don't update it.
                return TRUE;
        }
        if (gGLManager.mIsDisabled)
        {
                return TRUE;
        }

        static S32 next_frame = 0;
        const S32 total_no_tiles = 6 * NUM_TILES;
        const S32 cycle_frame_no = total_no_tiles + 1;

        if (mUpdateTimer.getElapsedTimeF32() > 0.001f)
        {
                mUpdateTimer.reset();
                const S32 frame = next_frame;

                ++next_frame;
                next_frame = next_frame % cycle_frame_no;

                sInterpVal = (!mInitialized) ? 1 : (F32)next_frame / cycle_frame_no;
                // sInterpVal = (F32)next_frame / cycle_frame_no;
                LLSkyTex::setInterpVal( sInterpVal );
                LLHeavenBody::setInterpVal( sInterpVal );
                calcAtmospherics();

                if (mForceUpdate || total_no_tiles == frame)
                {
                        LLSkyTex::stepCurrent();
                        
                        const static F32 LIGHT_DIRECTION_THRESHOLD = (F32) cos(DEG_TO_RAD * 1.f);
                        const static F32 COLOR_CHANGE_THRESHOLD = 0.01f;

                        LLVector3 direction = mSun.getDirection();
                        direction.normVec();
                        const F32 dot_lighting = direction * mLastLightingDirection;

                        LLColor3 delta_color;
                        delta_color.setVec(mLastTotalAmbient.mV[0] - mTotalAmbient.mV[0],
                                                           mLastTotalAmbient.mV[1] - mTotalAmbient.mV[1],
                                                           mLastTotalAmbient.mV[2] - mTotalAmbient.mV[2]);

                        if ( mForceUpdate 
                                 || ((dot_lighting < LIGHT_DIRECTION_THRESHOLD)
                                 || (delta_color.magVec() > COLOR_CHANGE_THRESHOLD)
                                 || !mInitialized)
                                && !direction.isExactlyZero())
                        {
                                mLastLightingDirection = direction;
                                mLastTotalAmbient = mTotalAmbient;
                                mInitialized = TRUE;

                                if (mCubeMap)
                                {
                    if (mForceUpdate)
                                        {
                                                updateFog(LLViewerCamera::getInstance()->getFar());
                                                for (int side = 0; side < 6; side++) 
                                                {
                                                        for (int tile = 0; tile < NUM_TILES; tile++) 
                                                        {
                                                                createSkyTexture(side, tile);
                                                        }
                                                }

                                                calcAtmospherics();

                                                for (int side = 0; side < 6; side++) 
                                                {
                                                        LLImageRaw* raw1 = mSkyTex[side].getImageRaw(TRUE);
                                                        LLImageRaw* raw2 = mSkyTex[side].getImageRaw(FALSE);
                                                        raw2->copy(raw1);
                                                        mSkyTex[side].createGLImage(mSkyTex[side].getWhich(FALSE));

                                                        raw1 = mShinyTex[side].getImageRaw(TRUE);
                                                        raw2 = mShinyTex[side].getImageRaw(FALSE);
                                                        raw2->copy(raw1);
                                                        mShinyTex[side].createGLImage(mShinyTex[side].getWhich(FALSE));
                                                }
                                                next_frame = 0; 
                                        }
                                }
                        }


                        // update the sky texture
                        for (S32 i = 0; i < 6; ++i)
                        {
                                mSkyTex[i].create(1.0f);
                                mShinyTex[i].create(1.0f);
                        }
                        
                        // update the environment map
                        if (mCubeMap)
                        {
                                std::vector<LLPointer<LLImageRaw> > images;
                                images.reserve(6);
                                for (S32 side = 0; side < 6; side++)
                                {
                                        images.push_back(mShinyTex[side].getImageRaw(TRUE));
                                }
                                mCubeMap->init(images);
                        }

                        gPipeline.markRebuild(gSky.mVOGroundp->mDrawable, LLDrawable::REBUILD_ALL, TRUE);
                        // *TODO: decide whether we need to update the stars vertex buffer in LLVOWLSky -Brad.
                        //gPipeline.markRebuild(gSky.mVOWLSkyp->mDrawable, LLDrawable::REBUILD_ALL, TRUE);

                        mForceUpdate = FALSE;
                }
                else
                {
                        const S32 side = frame / NUM_TILES;
                        const S32 tile = frame % NUM_TILES;
                        createSkyTexture(side, tile);
                }
        }

        if (mDrawable.notNull() && mDrawable->getFace(0) && mDrawable->getFace(0)->mVertexBuffer.isNull())
        {
                gPipeline.markRebuild(mDrawable, LLDrawable::REBUILD_VOLUME, TRUE);
        }
        return TRUE;
}

void LLVOSky::updateTextures(LLAgent &agent)
{
        if (mSunTexturep)
        {
                mSunTexturep->addTextureStats( (F32)MAX_IMAGE_AREA );
                mMoonTexturep->addTextureStats( (F32)MAX_IMAGE_AREA );
                mBloomTexturep->addTextureStats( (F32)MAX_IMAGE_AREA );
        }
}

LLDrawable *LLVOSky::createDrawable(LLPipeline *pipeline)
{
        pipeline->allocDrawable(this);
        mDrawable->setLit(FALSE);

        LLDrawPoolSky *poolp = (LLDrawPoolSky*) gPipeline.getPool(LLDrawPool::POOL_SKY);
        poolp->setSkyTex(mSkyTex);
        poolp->setSun(&mSun);
        poolp->setMoon(&mMoon);
        mDrawable->setRenderType(LLPipeline::RENDER_TYPE_SKY);
        
        for (S32 i = 0; i < 6; ++i)
        {
                mFace[FACE_SIDE0 + i] = mDrawable->addFace(poolp, NULL);
        }

        mFace[FACE_SUN] = mDrawable->addFace(poolp, mSunTexturep);
        mFace[FACE_MOON] = mDrawable->addFace(poolp, mMoonTexturep);
        mFace[FACE_BLOOM] = mDrawable->addFace(poolp, mBloomTexturep);

        return mDrawable;
}

//by bao
//fake vertex buffer updating
//to guaranttee at least updating one VBO buffer every frame
//to walk around the bug caused by ATI card --> DEV-3855
//
void LLVOSky::createDummyVertexBuffer()
{
        if(!mFace[FACE_DUMMY])
        {
                LLDrawPoolSky *poolp = (LLDrawPoolSky*) gPipeline.getPool(LLDrawPool::POOL_SKY);
                mFace[FACE_DUMMY] = mDrawable->addFace(poolp, NULL);
        }

        if(mFace[FACE_DUMMY]->mVertexBuffer.isNull())
        {
                mFace[FACE_DUMMY]->mVertexBuffer = new LLVertexBuffer(LLDrawPoolSky::VERTEX_DATA_MASK, GL_DYNAMIC_DRAW_ARB);
                mFace[FACE_DUMMY]->mVertexBuffer->allocateBuffer(1, 1, TRUE);
        }
}

void LLVOSky::updateDummyVertexBuffer()
{       
        if(!LLVertexBuffer::sEnableVBOs)
                return ;

        if(mHeavenlyBodyUpdated)
        {
                mHeavenlyBodyUpdated = FALSE ;
                return ;
        }

        LLFastTimer t(LLFastTimer::FTM_RENDER_FAKE_VBO_UPDATE) ;

        if(!mFace[FACE_DUMMY] || mFace[FACE_DUMMY]->mVertexBuffer.isNull())
                createDummyVertexBuffer() ;

        LLStrider<LLVector3> vertices ;
        mFace[FACE_DUMMY]->mVertexBuffer->getVertexStrider(vertices,  0);
        *vertices = mCameraPosAgent ;
        mFace[FACE_DUMMY]->mVertexBuffer->setBuffer(0) ;
}
//----------------------------------
//end of fake vertex buffer updating
//----------------------------------

BOOL LLVOSky::updateGeometry(LLDrawable *drawable)
{
        LLFastTimer ftm(LLFastTimer::FTM_GEO_SKY);
        if (mFace[FACE_REFLECTION] == NULL)
        {
                LLDrawPoolWater *poolp = (LLDrawPoolWater*) gPipeline.getPool(LLDrawPool::POOL_WATER);
                if (gPipeline.getPool(LLDrawPool::POOL_WATER)->getVertexShaderLevel() != 0)
                {
                        mFace[FACE_REFLECTION] = drawable->addFace(poolp, NULL);
                }
        }

        mCameraPosAgent = drawable->getPositionAgent();
        mEarthCenter.mV[0] = mCameraPosAgent.mV[0];
        mEarthCenter.mV[1] = mCameraPosAgent.mV[1];

        LLVector3 v_agent[8];
        for (S32 i = 0; i < 8; ++i)
        {
                F32 x_sgn = (i&1) ? 1.f : -1.f;
                F32 y_sgn = (i&2) ? 1.f : -1.f;
                F32 z_sgn = (i&4) ? 1.f : -1.f;
                v_agent[i] = HORIZON_DIST * SKY_BOX_MULT * LLVector3(x_sgn, y_sgn, z_sgn);
        }

        LLStrider<LLVector3> verticesp;
        LLStrider<LLVector3> normalsp;
        LLStrider<LLVector2> texCoordsp;
        LLStrider<U16> indicesp;
        U16 index_offset;
        LLFace *face;   

        for (S32 side = 0; side < 6; ++side)
        {
                face = mFace[FACE_SIDE0 + side]; 

                if (face->mVertexBuffer.isNull())
                {
                        face->setSize(4, 6);
                        face->setGeomIndex(0);
                        face->setIndicesIndex(0);
                        face->mVertexBuffer = new LLVertexBuffer(LLDrawPoolSky::VERTEX_DATA_MASK, GL_STREAM_DRAW_ARB);
                        face->mVertexBuffer->allocateBuffer(4, 6, TRUE);
                        
                        index_offset = face->getGeometry(verticesp,normalsp,texCoordsp, indicesp);
                        
                        S32 vtx = 0;
                        S32 curr_bit = side >> 1; // 0/1 = Z axis, 2/3 = Y, 4/5 = X
                        S32 side_dir = side & 1;  // even - 0, odd - 1
                        S32 i_bit = (curr_bit + 2) % 3;
                        S32 j_bit = (i_bit + 2) % 3;

                        LLVector3 axis;
                        axis.mV[curr_bit] = 1;
                        face->mCenterAgent = (F32)((side_dir << 1) - 1) * axis * HORIZON_DIST;

                        vtx = side_dir << curr_bit;
                        *(verticesp++)  = v_agent[vtx];
                        *(verticesp++)  = v_agent[vtx | 1 << j_bit];
                        *(verticesp++)  = v_agent[vtx | 1 << i_bit];
                        *(verticesp++)  = v_agent[vtx | 1 << i_bit | 1 << j_bit];

                        *(texCoordsp++) = TEX00;
                        *(texCoordsp++) = TEX01;
                        *(texCoordsp++) = TEX10;
                        *(texCoordsp++) = TEX11;

                        // Triangles for each side
                        *indicesp++ = index_offset + 0;
                        *indicesp++ = index_offset + 1;
                        *indicesp++ = index_offset + 3;

                        *indicesp++ = index_offset + 0;
                        *indicesp++ = index_offset + 3;
                        *indicesp++ = index_offset + 2;

                        face->mVertexBuffer->setBuffer(0);
                }
        }

        const LLVector3 &look_at = LLViewerCamera::getInstance()->getAtAxis();
        LLVector3 right = look_at % LLVector3::z_axis;
        LLVector3 up = right % look_at;
        right.normVec();
        up.normVec();

        const static F32 elevation_factor = 0.0f/sResolution;
        const F32 cos_max_angle = cosHorizon(elevation_factor);
        mSun.setDraw(updateHeavenlyBodyGeometry(drawable, FACE_SUN, TRUE, mSun, cos_max_angle, up, right));
        mMoon.setDraw(updateHeavenlyBodyGeometry(drawable, FACE_MOON, FALSE, mMoon, cos_max_angle, up, right));

        const F32 water_height = gAgent.getRegion()->getWaterHeight() + 0.01f;
                // LLWorld::getInstance()->getWaterHeight() + 0.01f;
        const F32 camera_height = mCameraPosAgent.mV[2];
        const F32 height_above_water = camera_height - water_height;

        BOOL sun_flag = FALSE;

        if (mSun.isVisible())
        {
                if (mMoon.isVisible())
                {
                        sun_flag = look_at * mSun.getDirection() > 0;
                }
                else
                {
                        sun_flag = TRUE;
                }
        }
        
        if (height_above_water > 0)
        {
                BOOL render_ref = gPipeline.getPool(LLDrawPool::POOL_WATER)->getVertexShaderLevel() == 0;

                if (sun_flag)
                {
                        setDrawRefl(0);
                        if (render_ref)
                        {
                                updateReflectionGeometry(drawable, height_above_water, mSun);
                        }
                }
                else
                {
                        setDrawRefl(1);
                        if (render_ref)
                        {
                                updateReflectionGeometry(drawable, height_above_water, mMoon);
                        }
                }
        }
        else
        {
                setDrawRefl(-1);
        }

        LLPipeline::sCompiles++;
        return TRUE;
}

BOOL LLVOSky::updateHeavenlyBodyGeometry(LLDrawable *drawable, const S32 f, const BOOL is_sun,
                                                                                 LLHeavenBody& hb, const F32 cos_max_angle,
                                                                                 const LLVector3 &up, const LLVector3 &right)
{
        mHeavenlyBodyUpdated = TRUE ;

        LLStrider<LLVector3> verticesp;
        LLStrider<LLVector3> normalsp;
        LLStrider<LLVector2> texCoordsp;
        LLStrider<U16> indicesp;
        S32 index_offset;
        LLFace *facep;

        LLVector3 to_dir = hb.getDirection();

        if (!is_sun)
        {
                to_dir.mV[2] = llmax(to_dir.mV[2]+0.1f, 0.1f);
        }
        LLVector3 draw_pos = to_dir * HEAVENLY_BODY_DIST;


        LLVector3 hb_right = to_dir % LLVector3::z_axis;
        LLVector3 hb_up = hb_right % to_dir;
        hb_right.normVec();
        hb_up.normVec();

        //const static F32 cos_max_turn = sqrt(3.f) / 2; // 30 degrees
        //const F32 cos_turn_right = 1. / (llmax(cos_max_turn, hb_right * right));
        //const F32 cos_turn_up = 1. / llmax(cos_max_turn, hb_up * up);

        const F32 enlargm_factor = ( 1 - to_dir.mV[2] );
        F32 horiz_enlargement = 1 + enlargm_factor * 0.3f;
        F32 vert_enlargement = 1 + enlargm_factor * 0.2f;

        // Parameters for the water reflection
        hb.setU(HEAVENLY_BODY_FACTOR * horiz_enlargement * hb.getDiskRadius() * hb_right);
        hb.setV(HEAVENLY_BODY_FACTOR * vert_enlargement * hb.getDiskRadius() * hb_up);
        // End of parameters for the water reflection

        const LLVector3 scaled_right = HEAVENLY_BODY_DIST * hb.getU();
        const LLVector3 scaled_up = HEAVENLY_BODY_DIST * hb.getV();

        //const LLVector3 scaled_right = horiz_enlargement * HEAVENLY_BODY_SCALE * hb.getDiskRadius() * hb_right;//right;
        //const LLVector3 scaled_up = vert_enlargement * HEAVENLY_BODY_SCALE * hb.getDiskRadius() * hb_up;//up;
        LLVector3 v_clipped[4];

        hb.corner(0) = draw_pos - scaled_right + scaled_up;
        hb.corner(1) = draw_pos - scaled_right - scaled_up;
        hb.corner(2) = draw_pos + scaled_right + scaled_up;
        hb.corner(3) = draw_pos + scaled_right - scaled_up;


        F32 t_left, t_right;
        if (!clip_quad_to_horizon(t_left, t_right, v_clipped, hb.corners(), cos_max_angle))
        {
                hb.setVisible(FALSE);
                return FALSE;
        }
        hb.setVisible(TRUE);

        facep = mFace[f]; 

        if (facep->mVertexBuffer.isNull())
        {
                facep->setSize(4, 6);           
                facep->mVertexBuffer = new LLVertexBuffer(LLDrawPoolSky::VERTEX_DATA_MASK, GL_STREAM_DRAW_ARB);
                facep->mVertexBuffer->allocateBuffer(facep->getGeomCount(), facep->getIndicesCount(), TRUE);
                facep->setGeomIndex(0);
                facep->setIndicesIndex(0);
        }

        index_offset = facep->getGeometry(verticesp,normalsp,texCoordsp, indicesp);

        if (-1 == index_offset)
        {
                return TRUE;
        }

        for (S32 vtx = 0; vtx < 4; ++vtx)
        {
                hb.corner(vtx) = v_clipped[vtx];
                *(verticesp++)  = hb.corner(vtx) + mCameraPosAgent;
        }

        *(texCoordsp++) = TEX01;
        *(texCoordsp++) = TEX00;
        *(texCoordsp++) = TEX11;
        *(texCoordsp++) = TEX10;

        *indicesp++ = index_offset + 0;
        *indicesp++ = index_offset + 2;
        *indicesp++ = index_offset + 1;

        *indicesp++ = index_offset + 1;
        *indicesp++ = index_offset + 2;
        *indicesp++ = index_offset + 3;

        facep->mVertexBuffer->setBuffer(0);

        if (is_sun)
        {
                if ((t_left > 0) && (t_right > 0))
                {
                        F32 t = (t_left + t_right) * 0.5f;
                        mSun.setHorizonVisibility(0.5f * (1 + cos(t * F_PI)));
                }
                else
                {
                        mSun.setHorizonVisibility();
                }
                updateSunHaloGeometry(drawable);
        }

        return TRUE;
}




// Clips quads with top and bottom sides parallel to horizon.

BOOL clip_quad_to_horizon(F32& t_left, F32& t_right, LLVector3 v_clipped[4],
                                                  const LLVector3 v_corner[4], const F32 cos_max_angle)
{
        t_left = clip_side_to_horizon(v_corner[1], v_corner[0], cos_max_angle);
        t_right = clip_side_to_horizon(v_corner[3], v_corner[2], cos_max_angle);

        if ((t_left >= 1) || (t_right >= 1))
        {
                return FALSE;
        }

        //const BOOL left_clip = (t_left > 0);
        //const BOOL right_clip = (t_right > 0);

        //if (!left_clip && !right_clip)
        {
                for (S32 vtx = 0; vtx < 4; ++vtx)
                {
                        v_clipped[vtx]  = v_corner[vtx];
                }
        }
/*      else
        {
                v_clipped[0] = v_corner[0];
                v_clipped[1] = left_clip ? ((1 - t_left) * v_corner[1] + t_left * v_corner[0])
                                                                        : v_corner[1];
                v_clipped[2] = v_corner[2];
                v_clipped[3] = right_clip ? ((1 - t_right) * v_corner[3] + t_right * v_corner[2])
                                                                        : v_corner[3];
        }*/

        return TRUE;
}


F32 clip_side_to_horizon(const LLVector3& V0, const LLVector3& V1, const F32 cos_max_angle)
{
        const LLVector3 V = V1 - V0;
        const F32 k2 = 1.f/(cos_max_angle * cos_max_angle) - 1;
        const F32 A = V.mV[0] * V.mV[0] + V.mV[1] * V.mV[1] - k2 * V.mV[2] * V.mV[2];
        const F32 B = V0.mV[0] * V.mV[0] + V0.mV[1] * V.mV[1] - k2 * V0.mV[2] * V.mV[2];
        const F32 C = V0.mV[0] * V0.mV[0] + V0.mV[1] * V0.mV[1] - k2 * V0.mV[2] * V0.mV[2];

        if (fabs(A) < 1e-7)
        {
                return -0.1f;   // v0 is cone origin and v1 is on the surface of the cone.
        }

        const F32 det = sqrt(B*B - A*C);
        const F32 t1 = (-B - det) / A;
        const F32 t2 = (-B + det) / A;
        const F32 z1 = V0.mV[2] + t1 * V.mV[2];
        const F32 z2 = V0.mV[2] + t2 * V.mV[2];
        if (z1 * cos_max_angle < 0)
        {
                return t2;
        }
        else if (z2 * cos_max_angle < 0)
        {
                return t1;
        }
        else if ((t1 < 0) || (t1 > 1))
        {
                return t2;
        }
        else
        {
                return t1;
        }
}


void LLVOSky::updateSunHaloGeometry(LLDrawable *drawable )
{
#if 0
        const LLVector3* v_corner = mSun.corners();

        LLStrider<LLVector3> verticesp;
        LLStrider<LLVector3> normalsp;
        LLStrider<LLVector2> texCoordsp;
        LLStrider<U16> indicesp;
        S32 index_offset;
        LLFace *face;

        const LLVector3 right = 2 * (v_corner[2] - v_corner[0]);
        LLVector3 up = 2 * (v_corner[2] - v_corner[3]);
        up.normVec();
        F32 size = right.magVec();
        up = size * up;
        const LLVector3 draw_pos = 0.25 * (v_corner[0] + v_corner[1] + v_corner[2] + v_corner[3]);
        
        LLVector3 v_glow_corner[4];

        v_glow_corner[0] = draw_pos - right + up;
        v_glow_corner[1] = draw_pos - right - up;
        v_glow_corner[2] = draw_pos + right + up;
        v_glow_corner[3] = draw_pos + right - up;

        face = mFace[FACE_BLOOM]; 

        if (face->mVertexBuffer.isNull())
        {
                face->setSize(4, 6);
                face->setGeomIndex(0);
                face->setIndicesIndex(0);
                face->mVertexBuffer = new LLVertexBuffer(LLDrawPoolWater::VERTEX_DATA_MASK, GL_STREAM_DRAW_ARB);
                face->mVertexBuffer->allocateBuffer(4, 6, TRUE);
        }

        index_offset = face->getGeometry(verticesp,normalsp,texCoordsp, indicesp);
        if (-1 == index_offset)
        {
                return;
        }

        for (S32 vtx = 0; vtx < 4; ++vtx)
        {
                *(verticesp++)  = v_glow_corner[vtx] + mCameraPosAgent;
        }

        *(texCoordsp++) = TEX01;
        *(texCoordsp++) = TEX00;
        *(texCoordsp++) = TEX11;
        *(texCoordsp++) = TEX10;

        *indicesp++ = index_offset + 0;
        *indicesp++ = index_offset + 2;
        *indicesp++ = index_offset + 1;

        *indicesp++ = index_offset + 1;
        *indicesp++ = index_offset + 2;
        *indicesp++ = index_offset + 3;
#endif
}


F32 dtReflection(const LLVector3& p, F32 cos_dir_from_top, F32 sin_dir_from_top, F32 diff_angl_dir)
{
        LLVector3 P = p;
        P.normVec();

        const F32 cos_dir_angle = -P.mV[VZ];
        const F32 sin_dir_angle = sqrt(1 - cos_dir_angle * cos_dir_angle);

        F32 cos_diff_angles = cos_dir_angle * cos_dir_from_top
                                                                        + sin_dir_angle * sin_dir_from_top;

        F32 diff_angles;
        if (cos_diff_angles > (1 - 1e-7))
                diff_angles = 0;
        else
                diff_angles = acos(cos_diff_angles);

        const F32 rel_diff_angles = diff_angles / diff_angl_dir;
        const F32 dt = 1 - rel_diff_angles;

        return (dt < 0) ? 0 : dt;
}


F32 dtClip(const LLVector3& v0, const LLVector3& v1, F32 far_clip2)
{
        F32 dt_clip;
        const LLVector3 otrezok = v1 - v0;
        const F32 A = otrezok.magVecSquared();
        const F32 B = v0 * otrezok;
        const F32 C = v0.magVecSquared() - far_clip2;
        const F32 det = sqrt(B*B - A*C);
        dt_clip = (-B - det) / A;
        if ((dt_clip < 0) || (dt_clip > 1))
                dt_clip = (-B + det) / A;
        return dt_clip;
}


void LLVOSky::updateReflectionGeometry(LLDrawable *drawable, F32 H,
                                                                                 const LLHeavenBody& HB)
{
        const LLVector3 &look_at = LLViewerCamera::getInstance()->getAtAxis();
        // const F32 water_height = gAgent.getRegion()->getWaterHeight() + 0.001f;
        // LLWorld::getInstance()->getWaterHeight() + 0.001f;

        LLVector3 to_dir = HB.getDirection();
        LLVector3 hb_pos = to_dir * (HORIZON_DIST - 10);
        LLVector3 to_dir_proj = to_dir;
        to_dir_proj.mV[VZ] = 0;
        to_dir_proj.normVec();

        LLVector3 Right = to_dir % LLVector3::z_axis;
        LLVector3 Up = Right % to_dir;
        Right.normVec();
        Up.normVec();

        // finding angle between  look direction and sprite.
        LLVector3 look_at_right = look_at % LLVector3::z_axis;
        look_at_right.normVec();

        const static F32 cos_horizon_angle = cosHorizon(0.0f/sResolution);
        //const static F32 horizon_angle = acos(cos_horizon_angle);

        const F32 enlargm_factor = ( 1 - to_dir.mV[2] );
        F32 horiz_enlargement = 1 + enlargm_factor * 0.3f;
        F32 vert_enlargement = 1 + enlargm_factor * 0.2f;

        F32 vert_size = vert_enlargement * HEAVENLY_BODY_SCALE * HB.getDiskRadius();
        Right *= /*cos_lookAt_toDir */ horiz_enlargement * HEAVENLY_BODY_SCALE * HB.getDiskRadius();
        Up *= vert_size;

        LLVector3 v_corner[2];
        LLVector3 stretch_corner[2];

        LLVector3 top_hb = v_corner[0] = stretch_corner[0] = hb_pos - Right + Up;
        v_corner[1] = stretch_corner[1] = hb_pos - Right - Up;

        F32 dt_hor, dt;
        dt_hor = clip_side_to_horizon(v_corner[1], v_corner[0], cos_horizon_angle);

        LLVector2 TEX0t = TEX00;
        LLVector2 TEX1t = TEX10;
        LLVector3 lower_corner = v_corner[1];

        if ((dt_hor > 0) && (dt_hor < 1))
        {
                TEX0t = LLVector2(0, dt_hor);
                TEX1t = LLVector2(1, dt_hor);
                lower_corner = (1 - dt_hor) * v_corner[1] + dt_hor * v_corner[0];
        }
        else
                dt_hor = llmax(0.0f, llmin(1.0f, dt_hor));

        top_hb.normVec();
        const F32 cos_angle_of_view = fabs(top_hb.mV[VZ]);
        const F32 extension = llmin (5.0f, 1.0f / cos_angle_of_view);

        const S32 cols = 1;
        const S32 raws = lltrunc(16 * extension);
        S32 quads = cols * raws;

        stretch_corner[0] = lower_corner + extension * (stretch_corner[0] - lower_corner);
        stretch_corner[1] = lower_corner + extension * (stretch_corner[1] - lower_corner);

        dt = dt_hor;


        F32 cos_dir_from_top[2];

        LLVector3 dir = stretch_corner[0];
        dir.normVec();
        cos_dir_from_top[0] = dir.mV[VZ];

        dir = stretch_corner[1];
        dir.normVec();
        cos_dir_from_top[1] = dir.mV[VZ];

        const F32 sin_dir_from_top = sqrt(1 - cos_dir_from_top[0] * cos_dir_from_top[0]);
        const F32 sin_dir_from_top2 = sqrt(1 - cos_dir_from_top[1] * cos_dir_from_top[1]);
        const F32 cos_diff_dir = cos_dir_from_top[0] * cos_dir_from_top[1]
                                                        + sin_dir_from_top * sin_dir_from_top2;
        const F32 diff_angl_dir = acos(cos_diff_dir);

        v_corner[0] = stretch_corner[0];
        v_corner[1] = lower_corner;


        LLVector2 TEX0tt = TEX01;
        LLVector2 TEX1tt = TEX11;

        LLVector3 v_refl_corner[4];
        LLVector3 v_sprite_corner[4];

        S32 vtx;
        for (vtx = 0; vtx < 2; ++vtx)
        {
                LLVector3 light_proj = v_corner[vtx];
                light_proj.normVec();

                const F32 z = light_proj.mV[VZ];
                const F32 sin_angle = sqrt(1 - z * z);
                light_proj *= 1.f / sin_angle;
                light_proj.mV[VZ] = 0;
                const F32 to_refl_point = H * sin_angle / fabs(z);

                v_refl_corner[vtx] = to_refl_point * light_proj;
        }


        for (vtx = 2; vtx < 4; ++vtx)
        {
                const LLVector3 to_dir_vec = (to_dir_proj * v_refl_corner[vtx-2]) * to_dir_proj;
                v_refl_corner[vtx] = v_refl_corner[vtx-2] + 2 * (to_dir_vec - v_refl_corner[vtx-2]);
        }

        for (vtx = 0; vtx < 4; ++vtx)
                v_refl_corner[vtx].mV[VZ] -= H;

        S32 side = 0;
        LLVector3 refl_corn_norm[2];
        refl_corn_norm[0] = v_refl_corner[1];
        refl_corn_norm[0].normVec();
        refl_corn_norm[1] = v_refl_corner[3];
        refl_corn_norm[1].normVec();

        F32 cos_refl_look_at[2];
        cos_refl_look_at[0] = refl_corn_norm[0] * look_at;
        cos_refl_look_at[1] = refl_corn_norm[1] * look_at;

        if (cos_refl_look_at[1] > cos_refl_look_at[0])
        {
                side = 2;
        }

        //const F32 far_clip = (LLViewerCamera::getInstance()->getFar() - 0.01) / far_clip_factor;
        const F32 far_clip = 512;
        const F32 far_clip2 = far_clip*far_clip;

        F32 dt_clip;
        F32 vtx_near2, vtx_far2;

        if ((vtx_far2 = v_refl_corner[side].magVecSquared()) > far_clip2)
        {
                // whole thing is sprite: reflection is beyond far clip plane.
                dt_clip = 1.1f;
                quads = 1;
        }
        else if ((vtx_near2 = v_refl_corner[side+1].magVecSquared()) > far_clip2)
        {
                // part is reflection, the rest is sprite.
                dt_clip = dtClip(v_refl_corner[side + 1], v_refl_corner[side], far_clip2);
                const LLVector3 P = (1 - dt_clip) * v_refl_corner[side + 1] + dt_clip * v_refl_corner[side];

                F32 dt_tex = dtReflection(P, cos_dir_from_top[0], sin_dir_from_top, diff_angl_dir);

                dt = dt_tex;
                TEX0tt = LLVector2(0, dt);
                TEX1tt = LLVector2(1, dt);
                quads++;
        }
        else
        {
                // whole thing is correct reflection.
                dt_clip = -0.1f;
        }

        LLFace *face = mFace[FACE_REFLECTION]; 

        if (face->mVertexBuffer.isNull() || quads*4 != face->getGeomCount())
        {
                face->setSize(quads * 4, quads * 6);
                face->mVertexBuffer = new LLVertexBuffer(LLDrawPoolWater::VERTEX_DATA_MASK, GL_STREAM_DRAW_ARB);
                face->mVertexBuffer->allocateBuffer(face->getGeomCount(), face->getIndicesCount(), TRUE);
                face->setIndicesIndex(0);
                face->setGeomIndex(0);
        }
        
        LLStrider<LLVector3> verticesp;
        LLStrider<LLVector3> normalsp;
        LLStrider<LLVector2> texCoordsp;
        LLStrider<U16> indicesp;
        S32 index_offset;
        
        index_offset = face->getGeometry(verticesp,normalsp,texCoordsp, indicesp);
        if (-1 == index_offset)
        {
                return;
        }

        LLColor3 hb_col3 = HB.getInterpColor();
        hb_col3.clamp();
        const LLColor4 hb_col = LLColor4(hb_col3);

        const F32 min_attenuation = 0.4f;
        const F32 max_attenuation = 0.7f;
        const F32 attenuation = min_attenuation
                + cos_angle_of_view * (max_attenuation - min_attenuation);

        LLColor4 hb_refl_col = (1-attenuation) * hb_col + attenuation * mFogColor;
        face->setFaceColor(hb_refl_col);
        
        LLVector3 v_far[2];
        v_far[0] = v_refl_corner[1];
        v_far[1] = v_refl_corner[3];

        if(dt_clip > 0)
        {
                if (dt_clip >= 1)
                {
                        for (S32 vtx = 0; vtx < 4; ++vtx)
                        {
                                F32 ratio = far_clip / v_refl_corner[vtx].magVec();
                                *(verticesp++) = v_refl_corner[vtx] = ratio * v_refl_corner[vtx] + mCameraPosAgent;
                        }
                        const LLVector3 draw_pos = 0.25 *
                                (v_refl_corner[0] + v_refl_corner[1] + v_refl_corner[2] + v_refl_corner[3]);
                        face->mCenterAgent = draw_pos;
                }
                else
                {
                        F32 ratio = far_clip / v_refl_corner[1].magVec();
                        v_sprite_corner[1] = v_refl_corner[1] * ratio;

                        ratio = far_clip / v_refl_corner[3].magVec();
                        v_sprite_corner[3] = v_refl_corner[3] * ratio;

                        v_refl_corner[1] = (1 - dt_clip) * v_refl_corner[1] + dt_clip * v_refl_corner[0];
                        v_refl_corner[3] = (1 - dt_clip) * v_refl_corner[3] + dt_clip * v_refl_corner[2];
                        v_sprite_corner[0] = v_refl_corner[1];
                        v_sprite_corner[2] = v_refl_corner[3];

                        for (S32 vtx = 0; vtx < 4; ++vtx)
                        {
                                *(verticesp++) = v_sprite_corner[vtx] + mCameraPosAgent;
                        }

                        const LLVector3 draw_pos = 0.25 *
                                (v_refl_corner[0] + v_sprite_corner[1] + v_refl_corner[2] + v_sprite_corner[3]);
                        face->mCenterAgent = draw_pos;
                }

                *(texCoordsp++) = TEX0tt;
                *(texCoordsp++) = TEX0t;
                *(texCoordsp++) = TEX1tt;
                *(texCoordsp++) = TEX1t;

                *indicesp++ = index_offset + 0;
                *indicesp++ = index_offset + 2;
                *indicesp++ = index_offset + 1;

                *indicesp++ = index_offset + 1;
                *indicesp++ = index_offset + 2;
                *indicesp++ = index_offset + 3;

                index_offset += 4;
        }

        if (dt_clip < 1)
        {
                if (dt_clip <= 0)
                {
                        const LLVector3 draw_pos = 0.25 *
                                (v_refl_corner[0] + v_refl_corner[1] + v_refl_corner[2] + v_refl_corner[3]);
                        face->mCenterAgent = draw_pos;
                }

                const F32 raws_inv = 1.f/raws;
                const F32 cols_inv = 1.f/cols;
                LLVector3 left  = v_refl_corner[0] - v_refl_corner[1];
                LLVector3 right = v_refl_corner[2] - v_refl_corner[3];
                left *= raws_inv;
                right *= raws_inv;

                F32 dt_raw = dt;

                for (S32 raw = 0; raw < raws; ++raw)
                {
                        F32 dt_v0 = raw * raws_inv;
                        F32 dt_v1 = (raw + 1) * raws_inv;
                        const LLVector3 BL = v_refl_corner[1] + (F32)raw * left;
                        const LLVector3 BR = v_refl_corner[3] + (F32)raw * right;
                        const LLVector3 EL = BL + left;
                        const LLVector3 ER = BR + right;
                        dt_v0 = dt_raw;
                        dt_raw = dt_v1 = dtReflection(EL, cos_dir_from_top[0], sin_dir_from_top, diff_angl_dir);
                        for (S32 col = 0; col < cols; ++col)
                        {
                                F32 dt_h0 = col * cols_inv;
                                *(verticesp++) = (1 - dt_h0) * EL + dt_h0 * ER + mCameraPosAgent;
                                *(verticesp++) = (1 - dt_h0) * BL + dt_h0 * BR + mCameraPosAgent;
                                F32 dt_h1 = (col + 1) * cols_inv;
                                *(verticesp++) = (1 - dt_h1) * EL + dt_h1 * ER + mCameraPosAgent;
                                *(verticesp++) = (1 - dt_h1) * BL + dt_h1 * BR + mCameraPosAgent;

                                *(texCoordsp++) = LLVector2(dt_h0, dt_v1);
                                *(texCoordsp++) = LLVector2(dt_h0, dt_v0);
                                *(texCoordsp++) = LLVector2(dt_h1, dt_v1);
                                *(texCoordsp++) = LLVector2(dt_h1, dt_v0);

                                *indicesp++ = index_offset + 0;
                                *indicesp++ = index_offset + 2;
                                *indicesp++ = index_offset + 1;

                                *indicesp++ = index_offset + 1;
                                *indicesp++ = index_offset + 2;
                                *indicesp++ = index_offset + 3;

                                index_offset += 4;
                        }
                }
        }

        face->mVertexBuffer->setBuffer(0);
}




void LLVOSky::updateFog(const F32 distance)
{
        if (!gPipeline.hasRenderDebugFeatureMask(LLPipeline::RENDER_DEBUG_FEATURE_FOG))
        {
                glFogf(GL_FOG_DENSITY, 0);
                glFogfv(GL_FOG_COLOR, (F32 *) &LLColor4::white.mV);
                glFogf(GL_FOG_END, 1000000.f);
                return;
        }

        const BOOL hide_clip_plane = TRUE;
        LLColor4 target_fog(0.f, 0.2f, 0.5f, 0.f);

        const F32 water_height = gAgent.getRegion()->getWaterHeight();
        // LLWorld::getInstance()->getWaterHeight();
        F32 camera_height = gAgent.getCameraPositionAgent().mV[2];

        F32 near_clip_height = LLViewerCamera::getInstance()->getAtAxis().mV[VZ] * LLViewerCamera::getInstance()->getNear();
        camera_height += near_clip_height;

        F32 fog_distance = 0.f;
        LLColor3 res_color[3];

        LLColor3 sky_fog_color = LLColor3::white;
        LLColor3 render_fog_color = LLColor3::white;

        LLVector3 tosun = getToSunLast();
        const F32 tosun_z = tosun.mV[VZ];
        tosun.mV[VZ] = 0.f;
        tosun.normVec();
        LLVector3 perp_tosun;
        perp_tosun.mV[VX] = -tosun.mV[VY];
        perp_tosun.mV[VY] = tosun.mV[VX];
        LLVector3 tosun_45 = tosun + perp_tosun;
        tosun_45.normVec();

        F32 delta = 0.06f;
        tosun.mV[VZ] = delta;
        perp_tosun.mV[VZ] = delta;
        tosun_45.mV[VZ] = delta;
        tosun.normVec();
        perp_tosun.normVec();
        tosun_45.normVec();

        // Sky colors, just slightly above the horizon in the direction of the sun, perpendicular to the sun, and at a 45 degree angle to the sun.
        initAtmospherics();
        res_color[0] = calcSkyColorInDir(tosun);
        res_color[1] = calcSkyColorInDir(perp_tosun);
        res_color[2] = calcSkyColorInDir(tosun_45);

        sky_fog_color = color_norm(res_color[0] + res_color[1] + res_color[2]);

        F32 full_off = -0.25f;
        F32 full_on = 0.00f;
        F32 on = (tosun_z - full_off) / (full_on - full_off);
        on = llclamp(on, 0.01f, 1.f);
        sky_fog_color *= 0.5f * on;


        // We need to clamp these to non-zero, in order for the gamma correction to work. 0^y = ???
        S32 i;
        for (i = 0; i < 3; i++)
        {
                sky_fog_color.mV[i] = llmax(0.0001f, sky_fog_color.mV[i]);
        }

        color_gamma_correct(sky_fog_color);

        render_fog_color = sky_fog_color;

        F32 fog_density = 0.f;
        fog_distance = mFogRatio * distance;
        
        if (camera_height > water_height)
        {
                LLColor4 fog(render_fog_color);
                glFogfv(GL_FOG_COLOR, fog.mV);
                mGLFogCol = fog;

                if (hide_clip_plane)
                {
                        // For now, set the density to extend to the cull distance.
                        const F32 f_log = 2.14596602628934723963618357029f; // sqrt(fabs(log(0.01f)))
                        fog_density = f_log/fog_distance;
                        glFogi(GL_FOG_MODE, GL_EXP2);
                }
                else
                {
                        const F32 f_log = 4.6051701859880913680359829093687f; // fabs(log(0.01f))
                        fog_density = (f_log)/fog_distance;
                        glFogi(GL_FOG_MODE, GL_EXP);
                }
        }
        else
        {
                F32 depth = water_height - camera_height;
                
                // get the water param manager variables
                float water_fog_density = LLWaterParamManager::instance()->getFogDensity();
                LLColor4 water_fog_color = LLDrawPoolWater::sWaterFogColor.mV;
                
                // adjust the color based on depth.  We're doing linear approximations
                float depth_scale = gSavedSettings.getF32("WaterGLFogDepthScale");
                float depth_modifier = 1.0f - llmin(llmax(depth / depth_scale, 0.01f), 
                        gSavedSettings.getF32("WaterGLFogDepthFloor"));

                LLColor4 fogCol = water_fog_color * depth_modifier;
                fogCol.setAlpha(1);

                // set the gl fog color
                glFogfv(GL_FOG_COLOR, (F32 *) &fogCol.mV);
                mGLFogCol = fogCol;

                // set the density based on what the shaders use
                fog_density = water_fog_density * gSavedSettings.getF32("WaterGLFogDensityScale");
                glFogi(GL_FOG_MODE, GL_EXP2);
        }

        mFogColor = sky_fog_color;
        mFogColor.setAlpha(1);
        LLGLSFog gls_fog;

        glFogf(GL_FOG_END, fog_distance*2.2f);

        glFogf(GL_FOG_DENSITY, fog_density);

        glHint(GL_FOG_HINT, GL_NICEST);
        stop_glerror();
}

// static
void LLHaze::initClass()
{
        sAirScaSeaLevel = LLHaze::calcAirScaSeaLevel();
}



// Functions used a lot.


F32 color_norm_pow(LLColor3& col, F32 e, BOOL postmultiply)
{
        F32 mv = color_max(col);
        if (0 == mv)
        {
                return 0;
        }

        col *= 1.f / mv;
        color_pow(col, e);
        if (postmultiply)
        {
                col *= mv;
        }
        return mv;
}

// Returns angle (RADIANs) between the horizontal projection of "v" and the x_axis.
// Range of output is 0.0f to 2pi //359.99999...f
// Returns 0.0f when "v" = +/- z_axis.
F32 azimuth(const LLVector3 &v)
{
        F32 azimuth = 0.0f;
        if (v.mV[VX] == 0.0f)
        {
                if (v.mV[VY] > 0.0f)
                {
                        azimuth = F_PI * 0.5f;
                }
                else if (v.mV[VY] < 0.0f)
                {
                        azimuth = F_PI * 1.5f;// 270.f;
                }
        }
        else
        {
                azimuth = (F32) atan(v.mV[VY] / v.mV[VX]);
                if (v.mV[VX] < 0.0f)
                {
                        azimuth += F_PI;
                }
                else if (v.mV[VY] < 0.0f)
                {
                        azimuth += F_PI * 2;
                }
        }       
        return azimuth;
}

void LLVOSky::initSunDirection(const LLVector3 &sun_dir, const LLVector3 &sun_ang_velocity)
{
        LLVector3 sun_direction = (sun_dir.magVec() == 0) ? LLVector3::x_axis : sun_dir;
        sun_direction.normVec();
        mSun.setDirection(sun_direction);
        mSun.renewDirection();
        mSun.setAngularVelocity(sun_ang_velocity);
        mMoon.setDirection(-mSun.getDirection());
        mMoon.renewDirection();
        mLastLightingDirection = mSun.getDirection();

        calcAtmospherics();

        if ( !mInitialized )
        {
                init();
                LLSkyTex::stepCurrent();
        }               
}

void LLVOSky::setSunDirection(const LLVector3 &sun_dir, const LLVector3 &sun_ang_velocity)
{
        LLVector3 sun_direction = (sun_dir.magVec() == 0) ? LLVector3::x_axis : sun_dir;
        sun_direction.normVec();

        // Push the sun "South" as it approaches directly overhead so that we can always see bump mapping
        // on the upward facing faces of cubes.
        LLVector3 newDir = sun_direction;

        // Same as dot product with the up direction + clamp.
        F32 sunDot = llmax(0.f, newDir.mV[2]);
        sunDot *= sunDot;       

        // Create normalized vector that has the sunDir pushed south about an hour and change.
        LLVector3 adjustedDir = (newDir + LLVector3(0.f, -0.70711f, 0.70711f)) * 0.5f;

        // Blend between normal sun dir and adjusted sun dir based on how close we are
        // to having the sun overhead.
        mBumpSunDir = adjustedDir * sunDot + newDir * (1.0f - sunDot);
        mBumpSunDir.normVec();

        F32 dp = mLastLightingDirection * sun_direction;
        mSun.setDirection(sun_direction);
        mSun.setAngularVelocity(sun_ang_velocity);
        mMoon.setDirection(-sun_direction);
        calcAtmospherics();
        if (dp < 0.995f) { //the sun jumped a great deal, update immediately
                mForceUpdate = TRUE;
        }
}

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