llflexibleobject.cpp

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#include "llviewerprecompiledheaders.h"

#include "pipeline.h"
#include "lldrawpoolbump.h"
#include "llface.h"
#include "llflexibleobject.h"
#include "llglheaders.h"
#include "llsphere.h"
#include "llviewerobject.h"
#include "llimagegl.h"
#include "llagent.h"
#include "llsky.h"
#include "llviewercamera.h"
#include "llviewerimagelist.h"
#include "llviewercontrol.h"
#include "llviewerobjectlist.h"
#include "llviewerregion.h"
#include "llworld.h"

/*static*/ F32 LLVolumeImplFlexible::sUpdateFactor = 1.0f;

// LLFlexibleObjectData::pack/unpack now in llprimitive.cpp

//-----------------------------------------------
// constructor
//-----------------------------------------------
LLVolumeImplFlexible::LLVolumeImplFlexible(LLViewerObject* vo, LLFlexibleObjectData* attributes) :
                mVO(vo), mAttributes(attributes)
{
        static U32 seed = 0;
        mID = seed++;
        mInitialized = FALSE;
        mUpdated = FALSE;
        mInitializedRes = -1;
        mSimulateRes = 0;
        mFrameNum = 0;
        mRenderRes = 1;
}//-----------------------------------------------

LLVector3 LLVolumeImplFlexible::getFramePosition() const
{
        return mVO->getRenderPosition();
}

LLQuaternion LLVolumeImplFlexible::getFrameRotation() const
{
        return mVO->getRenderRotation();
}

void LLVolumeImplFlexible::onParameterChanged(U16 param_type, LLNetworkData *data, BOOL in_use, bool local_origin)
{
        if (param_type == LLNetworkData::PARAMS_FLEXIBLE)
        {
                mAttributes = (LLFlexibleObjectData*)data;
                setAttributesOfAllSections();
        }
}

void LLVolumeImplFlexible::onShift(const LLVector3 &shift_vector)
{       
        for (int section = 0; section < (1<<FLEXIBLE_OBJECT_MAX_SECTIONS)+1; ++section)
        {
                mSection[section].mPosition += shift_vector;    
        }
}

//-----------------------------------------------------------------------------------------------
void LLVolumeImplFlexible::setParentPositionAndRotationDirectly( LLVector3 p, LLQuaternion r )
{
        mParentPosition = p;
        mParentRotation = r;

}//-----------------------------------------------------------------------------------------------------

void LLVolumeImplFlexible::remapSections(LLFlexibleObjectSection *source, S32 source_sections,
                                                                                 LLFlexibleObjectSection *dest, S32 dest_sections)
{       
        S32 num_output_sections = 1<<dest_sections;
        LLVector3 scale = mVO->mDrawable->getScale();
        F32 source_section_length = scale.mV[VZ] / (F32)(1<<source_sections);
        F32 section_length = scale.mV[VZ] / (F32)num_output_sections;
        if (source_sections == -1)
        {
                // Generate all from section 0
                dest[0] = source[0];
                for (S32 section=0; section<num_output_sections; ++section)
                {
                        dest[section+1] = dest[section];
                        dest[section+1].mPosition += dest[section].mDirection * section_length;
                        dest[section+1].mVelocity.setVec( LLVector3::zero );
                }
        }
        else if (source_sections > dest_sections)
        {
                // Copy, skipping sections

                S32 num_steps = 1<<(source_sections-dest_sections);

                // Copy from left to right since it may be an in-place computation
                for (S32 section=0; section<num_output_sections; ++section)
                {
                        dest[section+1] = source[(section+1)*num_steps];
                }
                dest[0] = source[0];
        }
        else if (source_sections < dest_sections)
        {
                // Interpolate section info
                // Iterate from right to left since it may be an in-place computation
                S32 step_shift = dest_sections-source_sections;
                S32 num_steps = 1<<step_shift;
                for (S32 section=num_output_sections-num_steps; section>=0; section -= num_steps)
                {
                        LLFlexibleObjectSection *last_source_section = &source[section>>step_shift];
                        LLFlexibleObjectSection *source_section = &source[(section>>step_shift)+1];

                        // Cubic interpolation of position
                        // At^3 + Bt^2 + Ct + D = f(t)
                        LLVector3 D = last_source_section->mPosition;
                        LLVector3 C = last_source_section->mdPosition * source_section_length;
                        LLVector3 Y = source_section->mdPosition * source_section_length - C; // Helper var
                        LLVector3 X = (source_section->mPosition - D - C); // Helper var
                        LLVector3 A = Y - 2*X;
                        LLVector3 B = X - A;

                        F32 t_inc = 1.f/F32(num_steps);
                        F32 t = t_inc;
                        for (S32 step=1; step<num_steps; ++step)
                        {
                                dest[section+step].mScale = 
                                        lerp(last_source_section->mScale, source_section->mScale, t);
                                dest[section+step].mAxisRotation = 
                                        slerp(t, last_source_section->mAxisRotation, source_section->mAxisRotation);

                                // Evaluate output interpolated values
                                F32 t_sq = t*t;
                                dest[section+step].mPosition = t_sq*(t*A + B) + t*C + D;
                                dest[section+step].mRotation = 
                                        slerp(t, last_source_section->mRotation, source_section->mRotation);
                                dest[section+step].mVelocity = lerp(last_source_section->mVelocity, source_section->mVelocity, t);
                                dest[section+step].mDirection = lerp(last_source_section->mDirection, source_section->mDirection, t);
                                dest[section+step].mdPosition = lerp(last_source_section->mdPosition, source_section->mdPosition, t);
                                dest[section+num_steps] = *source_section;
                                t += t_inc;
                        }
                }
                dest[0] = source[0];
        }
        else
        {
                // numbers are equal. copy info
                for (S32 section=0; section <= num_output_sections; ++section)
                {
                        dest[section] = source[section];
                }
        }
}


//-----------------------------------------------------------------------------
void LLVolumeImplFlexible::setAttributesOfAllSections()
{
        LLVector2 bottom_scale, top_scale;
        F32 begin_rot = 0, end_rot = 0;
        if (mVO->getVolume())
        {
                const LLPathParams &params = mVO->getVolume()->getParams().getPathParams();
                bottom_scale = params.getBeginScale();
                top_scale = params.getEndScale();
                begin_rot = F_PI * params.getTwistBegin();
                end_rot = F_PI * params.getTwist();
        }

        if (!mVO->mDrawable)
        {
                return;
        }
        
        S32 num_sections = 1 << mSimulateRes;

        LLVector3 scale = mVO->mDrawable->getScale();
                                                                        
        mSection[0].mPosition = getAnchorPosition();
        mSection[0].mDirection = LLVector3::z_axis * getFrameRotation();
        mSection[0].mdPosition = mSection[0].mDirection;
        mSection[0].mScale.setVec(scale.mV[VX]*bottom_scale.mV[0], scale.mV[VY]*bottom_scale.mV[1]);
        mSection[0].mVelocity.setVec(0,0,0);
        mSection[0].mAxisRotation.setQuat(begin_rot,0,0,1);

        LLVector3 parentSectionPosition = mSection[0].mPosition;
        LLVector3 last_direction = mSection[0].mDirection;

        remapSections(mSection, mInitializedRes, mSection, mSimulateRes);
        mInitializedRes = mSimulateRes;

        F32 t_inc = 1.f/F32(num_sections);
        F32 t = t_inc;

        for ( int i=1; i<= num_sections; i++)
        {
                mSection[i].mAxisRotation.setQuat(lerp(begin_rot,end_rot,t),0,0,1);
                mSection[i].mScale = LLVector2(
                        scale.mV[VX] * lerp(bottom_scale.mV[0], top_scale.mV[0], t), 
                        scale.mV[VY] * lerp(bottom_scale.mV[1], top_scale.mV[1], t));
                t += t_inc;
        }
}//-----------------------------------------------------------------------------------


void LLVolumeImplFlexible::onSetVolume(const LLVolumeParams &volume_params, const S32 detail)
{
        /*doIdleUpdate(gAgent, *gWorldp, 0.0);
        if (mVO && mVO->mDrawable.notNull())
        {
                gPipeline.markRebuild(mVO->mDrawable, LLDrawable::REBUILD_VOLUME, TRUE);
                gPipeline.markMoved(mVO->mDrawable);
        }*/
}

//---------------------------------------------------------------------------------
// This calculates the physics of the flexible object. Note that it has to be 0
// updated every time step. In the future, perhaps there could be an 
// optimization similar to what Havok does for objects that are stationary. 
//---------------------------------------------------------------------------------
BOOL LLVolumeImplFlexible::doIdleUpdate(LLAgent &agent, LLWorld &world, const F64 &time)
{

        if (mVO->mDrawable.isNull())
        {
                // Don't do anything until we have a drawable
                return FALSE; // (we are not initialized or updated)
        }

        //flexible objects never go static
        mVO->mDrawable->mQuietCount = 0;
        if (!mVO->mDrawable->isRoot())
        {
                LLViewerObject* parent = (LLViewerObject*) mVO->getParent();
                parent->mDrawable->mQuietCount = 0;
        }

        LLFastTimer ftm(LLFastTimer::FTM_FLEXIBLE_UPDATE);
                
        S32 new_res = mAttributes->getSimulateLOD();

        //number of segments only cares about z axis
        F32 app_angle = llround((F32) atan2( mVO->getScale().mV[2]*2.f, mVO->mDrawable->mDistanceWRTCamera) * RAD_TO_DEG, 0.01f);

        // Rendering sections increases with visible angle on the screen
        mRenderRes = (S32)(FLEXIBLE_OBJECT_MAX_SECTIONS*4*app_angle*DEG_TO_RAD/gCamera->getView());
        if (mRenderRes > FLEXIBLE_OBJECT_MAX_SECTIONS)
        {
                mRenderRes = FLEXIBLE_OBJECT_MAX_SECTIONS;
        }


        // Bottom cap at 1/4 the original number of sections
        if (mRenderRes < mAttributes->getSimulateLOD()-1)
        {
                mRenderRes = mAttributes->getSimulateLOD()-1;
        }
        // Throttle back simulation of segments we're not rendering
        if (mRenderRes < new_res)
        {
                new_res = mRenderRes;
        }

        if (!mInitialized || (mSimulateRes != new_res))
        {
                mSimulateRes = new_res;
                setAttributesOfAllSections();
                mInitialized = TRUE;
        }
        if (!gPipeline.hasRenderDebugFeatureMask(LLPipeline::RENDER_DEBUG_FEATURE_FLEXIBLE))
        {
                return FALSE; // (we are not initialized or updated)
        }

        if (mVO->mDrawable->isVisible() &&
                !mVO->mDrawable->isState(LLDrawable::IN_REBUILD_Q1) &&
                mVO->getPixelArea() > 256.f)
        {
                U32 id;
                F32 pixel_area = mVO->getPixelArea();

                if (mVO->isRootEdit())
                {
                        id = mID;
                }
                else
                {
                        LLVOVolume* parent = (LLVOVolume*) mVO->getParent();
                        id = parent->getVolumeInterfaceID();
                }

                U32 update_period = (U32) (gCamera->getScreenPixelArea()*0.01f/(pixel_area*(sUpdateFactor+1.f)))+1;

                if ((LLDrawable::getCurrentFrame()+id)%update_period == 0)
                {
                        gPipeline.markRebuild(mVO->mDrawable, LLDrawable::REBUILD_POSITION, FALSE);
                }
        }
        
        return TRUE;
}

inline S32 log2(S32 x)
{
        S32 ret = 0;
        while (x > 1)
        {
                ++ret;
                x >>= 1;
        }
        return ret;
}

void LLVolumeImplFlexible::doFlexibleUpdate()
{
        LLPath *path = &mVO->getVolume()->getPath();
        if (mSimulateRes == 0)
        {
                mVO->markForUpdate(TRUE);
                if (!doIdleUpdate(gAgent, *gWorldp, 0.0))
                {
                        return; // we did not get updated or initialized, proceeding without can be dangerous
                }
        }

        llassert_always(mInitialized);
        
        S32 num_sections = 1 << mSimulateRes;

    F32 secondsThisFrame = mTimer.getElapsedTimeAndResetF32();
        if (secondsThisFrame > 0.2f)
        {
                secondsThisFrame = 0.2f;
        }

        LLVector3 BasePosition = getFramePosition();
        LLQuaternion BaseRotation = getFrameRotation();
        LLQuaternion parentSegmentRotation = BaseRotation;
        LLVector3 anchorDirectionRotated = LLVector3::z_axis * parentSegmentRotation;
        LLVector3 anchorScale = mVO->mDrawable->getScale();
        
        F32 section_length = anchorScale.mV[VZ] / (F32)num_sections;
        F32 inv_section_length = 1.f / section_length;

        S32 i;

        // ANCHOR position is offset from BASE position (centroid) by half the length
        LLVector3 AnchorPosition = BasePosition - (anchorScale.mV[VZ]/2 * anchorDirectionRotated);
        
        mSection[0].mPosition = AnchorPosition;
        mSection[0].mDirection = anchorDirectionRotated;
        mSection[0].mRotation = BaseRotation;

        LLQuaternion deltaRotation;

        LLVector3 lastPosition;

        // Coefficients which are constant across sections
        F32 t_factor = mAttributes->getTension() * 0.1f;
        t_factor = t_factor*(1 - pow(0.85f, secondsThisFrame*30));
        if ( t_factor > FLEXIBLE_OBJECT_MAX_INTERNAL_TENSION_FORCE )
        {
                t_factor = FLEXIBLE_OBJECT_MAX_INTERNAL_TENSION_FORCE;
        }

        F32 friction_coeff = (mAttributes->getAirFriction()*2+1);
        friction_coeff = pow(10.f, friction_coeff*secondsThisFrame);
        friction_coeff = (friction_coeff > 1) ? friction_coeff : 1;
        F32 momentum = 1.0f / friction_coeff;

        F32 wind_factor = (mAttributes->getWindSensitivity()*0.1f) * section_length * secondsThisFrame;
        F32 max_angle = atan(section_length*2.f);

        F32 force_factor = section_length * secondsThisFrame;

        // Update simulated sections
        for (i=1; i<=num_sections; ++i)
        {
                LLVector3 parentSectionVector;
                LLVector3 parentSectionPosition;
                LLVector3 parentDirection;

                //---------------------------------------------------
                // save value of position as lastPosition
                //---------------------------------------------------
                lastPosition = mSection[i].mPosition;

                //------------------------------------------------------------------------------------------
                // gravity
                //------------------------------------------------------------------------------------------
                mSection[i].mPosition.mV[2] -= mAttributes->getGravity() * force_factor;

                //------------------------------------------------------------------------------------------
                // wind force
                //------------------------------------------------------------------------------------------
                if (mAttributes->getWindSensitivity() > 0.001f)
                {
                        mSection[i].mPosition += gAgent.getRegion()->mWind.getVelocity( mSection[i].mPosition ) * wind_factor;
                }

                //------------------------------------------------------------------------------------------
                // user-defined force
                //------------------------------------------------------------------------------------------
                mSection[i].mPosition += mAttributes->getUserForce() * force_factor;

                //---------------------------------------------------
                // tension (rigidity, stiffness)
                //---------------------------------------------------
                parentSectionPosition = mSection[i-1].mPosition;
                parentDirection = mSection[i-1].mDirection;

                if ( i == 1 )
                {
                        parentSectionVector = mSection[0].mDirection;
                }
                else
                {
                        parentSectionVector = mSection[i-2].mDirection;
                }

                LLVector3 currentVector = mSection[i].mPosition - parentSectionPosition;

                LLVector3 difference = (parentSectionVector*section_length) - currentVector;
                LLVector3 tensionForce = difference * t_factor;

                mSection[i].mPosition += tensionForce;

                //------------------------------------------------------------------------------------------
                // sphere collision, currently not used
                //------------------------------------------------------------------------------------------
                /*if ( mAttributes->mUsingCollisionSphere )
                {
                        LLVector3 vectorToCenterOfCollisionSphere = mCollisionSpherePosition - mSection[i].mPosition;
                        if ( vectorToCenterOfCollisionSphere.magVecSquared() < mCollisionSphereRadius * mCollisionSphereRadius )
                        {
                                F32 distanceToCenterOfCollisionSphere = vectorToCenterOfCollisionSphere.magVec();
                                F32 penetration = mCollisionSphereRadius - distanceToCenterOfCollisionSphere;

                                LLVector3 normalToCenterOfCollisionSphere;
                                
                                if ( distanceToCenterOfCollisionSphere > 0.0f )
                                {
                                        normalToCenterOfCollisionSphere = vectorToCenterOfCollisionSphere / distanceToCenterOfCollisionSphere;
                                }
                                else // rare
                                {
                                        normalToCenterOfCollisionSphere = LLVector3::x_axis; // arbitrary
                                }

                                // push the position out to the surface of the collision sphere
                                mSection[i].mPosition -= normalToCenterOfCollisionSphere * penetration;
                        }
                }*/

                //------------------------------------------------------------------------------------------
                // inertia
                //------------------------------------------------------------------------------------------
                mSection[i].mPosition += mSection[i].mVelocity * momentum;

                //------------------------------------------------------------------------------------------
                // clamp length & rotation
                //------------------------------------------------------------------------------------------
                mSection[i].mDirection = mSection[i].mPosition - parentSectionPosition;
                mSection[i].mDirection.normVec();
                deltaRotation.shortestArc( parentDirection, mSection[i].mDirection );

                F32 angle;
                LLVector3 axis;
                deltaRotation.getAngleAxis(&angle, axis);
                if (angle > F_PI) angle -= 2.f*F_PI;
                if (angle < -F_PI) angle += 2.f*F_PI;
                if (angle > max_angle)
                {
                        //angle = 0.5f*(angle+max_angle);
                        deltaRotation.setQuat(max_angle, axis);
                } else if (angle < -max_angle)
                {
                        //angle = 0.5f*(angle-max_angle);
                        deltaRotation.setQuat(-max_angle, axis);
                }
                LLQuaternion segment_rotation = parentSegmentRotation * deltaRotation;
                parentSegmentRotation = segment_rotation;

                mSection[i].mDirection = (parentDirection * deltaRotation);
                mSection[i].mPosition = parentSectionPosition + mSection[i].mDirection * section_length;
                mSection[i].mRotation = segment_rotation;

                if (i > 1)
                {
                        // Propogate half the rotation up to the parent
                        LLQuaternion halfDeltaRotation(angle/2, axis);
                        mSection[i-1].mRotation = mSection[i-1].mRotation * halfDeltaRotation;
                }

                //------------------------------------------------------------------------------------------
                // calculate velocity
                //------------------------------------------------------------------------------------------
                mSection[i].mVelocity = mSection[i].mPosition - lastPosition;
                if (mSection[i].mVelocity.magVecSquared() > 1.f)
                {
                        mSection[i].mVelocity.normVec();
                }
        }

        // Calculate derivatives (not necessary until normals are automagically generated)
        mSection[0].mdPosition = (mSection[1].mPosition - mSection[0].mPosition) * inv_section_length;
        // i = 1..NumSections-1
        for (i=1; i<num_sections; ++i)
        {
                // Quadratic numerical derivative of position

                // f(-L1) = aL1^2 - bL1 + c = f1
                // f(0)   =               c = f2
                // f(L2)  = aL2^2 + bL2 + c = f3
                // f = ax^2 + bx + c
                // d/dx f = 2ax + b
                // d/dx f(0) = b

                // c = f2
                // a = [(f1-c)/L1 + (f3-c)/L2] / (L1+L2)
                // b = (f3-c-aL2^2)/L2

                LLVector3 a = (mSection[i-1].mPosition-mSection[i].mPosition +
                                        mSection[i+1].mPosition-mSection[i].mPosition) * 0.5f * inv_section_length * inv_section_length;
                LLVector3 b = (mSection[i+1].mPosition-mSection[i].mPosition - a*(section_length*section_length));
                b *= inv_section_length;

                mSection[i].mdPosition = b;
        }

        // i = NumSections
        mSection[i].mdPosition = (mSection[i].mPosition - mSection[i-1].mPosition) * inv_section_length;

        // Create points
        S32 num_render_sections = 1<<mRenderRes;
        path->resizePath(num_render_sections+1);

        LLPath::PathPt *new_point;

        LLFlexibleObjectSection newSection[ (1<<FLEXIBLE_OBJECT_MAX_SECTIONS)+1 ];
        remapSections(mSection, mSimulateRes, newSection, mRenderRes);

        //generate transform from global to prim space
        LLVector3 delta_scale = LLVector3(1,1,1);
        LLVector3 delta_pos;
        LLQuaternion delta_rot;

        delta_rot = ~getFrameRotation();
        delta_pos = -getFramePosition()*delta_rot;
                
        // Vertex transform (4x4)
        LLVector3 x_axis = LLVector3(delta_scale.mV[VX], 0.f, 0.f) * delta_rot;
        LLVector3 y_axis = LLVector3(0.f, delta_scale.mV[VY], 0.f) * delta_rot;
        LLVector3 z_axis = LLVector3(0.f, 0.f, delta_scale.mV[VZ]) * delta_rot;

        LLMatrix4 rel_xform;
        rel_xform.initRows(LLVector4(x_axis, 0.f),
                                                                LLVector4(y_axis, 0.f),
                                                                LLVector4(z_axis, 0.f),
                                                                LLVector4(delta_pos, 1.f));
                        
        for (i=0; i<=num_render_sections; ++i)
        {
                new_point = &path->mPath[i];
                LLVector3 pos = newSection[i].mPosition * rel_xform;
                LLQuaternion rot = mSection[i].mAxisRotation * newSection[i].mRotation * delta_rot;
                
                if (!mUpdated || (new_point->mPos-pos).magVecSquared() > 0.000001f)
                {
                        new_point->mPos = newSection[i].mPosition * rel_xform;
                        mUpdated = FALSE;
                }

                new_point->mRot = rot;
                new_point->mScale = newSection[i].mScale;
                new_point->mTexT = ((F32)i)/(num_render_sections);
        }

        mLastSegmentRotation = parentSegmentRotation;
}

void LLVolumeImplFlexible::doFlexibleRebuild()
{
        mVO->getVolume()->regen();
        mUpdated = TRUE;
}

//------------------------------------------------------------------

void LLVolumeImplFlexible::onSetScale(const LLVector3& scale, BOOL damped)
{
        setAttributesOfAllSections();
}

BOOL LLVolumeImplFlexible::doUpdateGeometry(LLDrawable *drawable)
{
        LLVOVolume *volume = (LLVOVolume*)mVO;

        if (volume->mDrawable.isNull()) // Not sure why this is happening, but it is...
        {
                return TRUE; // No update to complete
        }

        if (volume->mLODChanged)
        {
                LLVolumeParams volume_params = volume->getVolume()->getParams();
                volume->setVolume(volume_params, 0);
                mUpdated = FALSE;
        }

        volume->updateRelativeXform();
        doFlexibleUpdate();
        
        // Object may have been rotated, which means it needs a rebuild.  See SL-47220
        BOOL    rotated = FALSE;
        LLQuaternion cur_rotation = getFrameRotation();
        if ( cur_rotation != mLastFrameRotation )
        {
                mLastFrameRotation = cur_rotation;
                rotated = TRUE;
        }

        if (volume->mLODChanged || volume->mFaceMappingChanged ||
                volume->mVolumeChanged)
        {
                volume->regenFaces();
                volume->mDrawable->setState(LLDrawable::REBUILD_VOLUME);
        }

        if (!mUpdated || volume->mFaceMappingChanged || volume->mVolumeChanged || rotated)
        {
                doFlexibleRebuild();
                volume->genBBoxes(isVolumeGlobal());
        }
                        
        volume->mVolumeChanged = FALSE;
        volume->mLODChanged = FALSE;
        volume->mFaceMappingChanged = FALSE;


        // clear UV flag
        drawable->clearState(LLDrawable::UV);
        
        return TRUE;
}

//----------------------------------------------------------------------------------
void LLVolumeImplFlexible::setCollisionSphere( LLVector3 p, F32 r )
{
        mCollisionSpherePosition = p;
        mCollisionSphereRadius   = r;

}//------------------------------------------------------------------


//----------------------------------------------------------------------------------
void LLVolumeImplFlexible::setUsingCollisionSphere( bool u )
{
}//------------------------------------------------------------------


//----------------------------------------------------------------------------------
void LLVolumeImplFlexible::setRenderingCollisionSphere( bool r )
{
}//------------------------------------------------------------------

//------------------------------------------------------------------
LLVector3 LLVolumeImplFlexible::getEndPosition()
{
        S32 num_sections = 1 << mAttributes->getSimulateLOD();
        return mSection[ num_sections ].mPosition;

}//------------------------------------------------------------------


//------------------------------------------------------------------
LLVector3 LLVolumeImplFlexible::getNodePosition( int nodeIndex )
{
        S32 num_sections = 1 << mAttributes->getSimulateLOD();
        if ( nodeIndex > num_sections - 1 )
        {
                nodeIndex = num_sections - 1;
        }
        else if ( nodeIndex < 0 ) 
        {
                nodeIndex = 0;
        }

        return mSection[ nodeIndex ].mPosition;

}//------------------------------------------------------------------

LLVector3 LLVolumeImplFlexible::getPivotPosition() const
{
        return getAnchorPosition();
}

//------------------------------------------------------------------
LLVector3 LLVolumeImplFlexible::getAnchorPosition() const
{
        LLVector3 BasePosition = getFramePosition();
        LLQuaternion parentSegmentRotation = getFrameRotation();
        LLVector3 anchorDirectionRotated = LLVector3::z_axis * parentSegmentRotation;
        LLVector3 anchorScale = mVO->mDrawable->getScale();
        return BasePosition - (anchorScale.mV[VZ]/2 * anchorDirectionRotated);

}//------------------------------------------------------------------


//------------------------------------------------------------------
LLQuaternion LLVolumeImplFlexible::getEndRotation()
{
        return mLastSegmentRotation;

}//------------------------------------------------------------------


void LLVolumeImplFlexible::updateRelativeXform()
{
        LLQuaternion delta_rot;
        LLVector3 delta_pos, delta_scale;
        LLVOVolume* vo = (LLVOVolume*) mVO;

        //matrix from local space to parent relative/global space
        delta_rot = vo->mDrawable->isSpatialRoot() ? LLQuaternion() : vo->mDrawable->getRotation();
        delta_pos = vo->mDrawable->isSpatialRoot() ? LLVector3(0,0,0) : vo->mDrawable->getPosition();
        delta_scale = LLVector3(1,1,1);

        // Vertex transform (4x4)
        LLVector3 x_axis = LLVector3(delta_scale.mV[VX], 0.f, 0.f) * delta_rot;
        LLVector3 y_axis = LLVector3(0.f, delta_scale.mV[VY], 0.f) * delta_rot;
        LLVector3 z_axis = LLVector3(0.f, 0.f, delta_scale.mV[VZ]) * delta_rot;

        vo->mRelativeXform.initRows(LLVector4(x_axis, 0.f),
                                                        LLVector4(y_axis, 0.f),
                                                        LLVector4(z_axis, 0.f),
                                                        LLVector4(delta_pos, 1.f));
                        
        x_axis.normVec();
        y_axis.normVec();
        z_axis.normVec();
        
        vo->mRelativeXformInvTrans.setRows(x_axis, y_axis, z_axis);
}

const LLMatrix4& LLVolumeImplFlexible::getWorldMatrix(LLXformMatrix* xform) const
{
        return xform->getWorldMatrix();
}

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