llviewerlayer.cpp

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#include "llviewerprecompiledheaders.h"

#include "llviewerlayer.h"
#include "llerror.h"
#include "llmath.h"

LLViewerLayer::LLViewerLayer(const S32 width, const F32 scale)
{
        mWidth = width;
        mScale = scale;
        mScaleInv = 1.f/scale;
        mDatap = new F32[width*width];

        for (S32 i = 0; i < width*width; i++)
        {
                *(mDatap + i) = 0.f;
        }
}

LLViewerLayer::~LLViewerLayer()
{
        delete[] mDatap;
        mDatap = NULL;
}

F32 LLViewerLayer::getValue(const S32 x, const S32 y) const
{
//      llassert(x >= 0);
//      llassert(x < mWidth);
//      llassert(y >= 0);
//      llassert(y < mWidth);

        return *(mDatap + x + y*mWidth);
}

F32 LLViewerLayer::getValueScaled(const F32 x, const F32 y) const
{
        S32 x1, x2, y1, y2;
        F32 x_frac, y_frac;

        x_frac = x*mScaleInv;
        x1 = llfloor(x_frac);
        x2 = x1 + 1;
        x_frac -= x1;

        y_frac = y*mScaleInv;
        y1 = llfloor(y_frac);
        y2 = y1 + 1;
        y_frac -= y1;

        x1 = llmin((S32)mWidth-1, x1);
        x1 = llmax(0, x1);
        x2 = llmin((S32)mWidth-1, x2);
        x2 = llmax(0, x2);
        y1 = llmin((S32)mWidth-1, y1);
        y1 = llmax(0, y1);
        y2 = llmin((S32)mWidth-1, y2);
        y2 = llmax(0, y2);

        // Take weighted average of all four points (bilinear interpolation)
        S32 row1 = y1 * mWidth;
        S32 row2 = y2 * mWidth;
        
        // Access in squential order in memory, and don't use immediately.
        F32 row1_left  = mDatap[ row1 + x1 ];
        F32 row1_right = mDatap[ row1 + x2 ];
        F32 row2_left  = mDatap[ row2 + x1 ];
        F32 row2_right = mDatap[ row2 + x2 ];
        
        F32 row1_interp = row1_left - x_frac * (row1_left - row1_right);
        F32 row2_interp = row2_left - x_frac * (row2_left - row2_right);
        
        return row1_interp - y_frac * (row1_interp - row2_interp);
}

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