source: code/branches/physics/src/bullet/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp @ 1983

/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, 
including commercial applications, and to alter it and redistribute it freely, 
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/

#include "btHeightfieldTerrainShape.h"

#include "LinearMath/btTransformUtil.h"


btHeightfieldTerrainShape::btHeightfieldTerrainShape(int heightStickWidth, int heightStickLength,void* heightfieldData,btScalar maxHeight,int upAxis,bool useFloatData,bool flipQuadEdges)
: btConcaveShape (), m_heightStickWidth(heightStickWidth),
m_heightStickLength(heightStickLength),
m_maxHeight(maxHeight),
m_width((btScalar)heightStickWidth-1),
m_length((btScalar)heightStickLength-1),
m_heightfieldDataUnknown(heightfieldData),
m_useFloatData(useFloatData),
m_flipQuadEdges(flipQuadEdges),
m_useDiamondSubdivision(false),
m_upAxis(upAxis),
m_localScaling(btScalar(1.),btScalar(1.),btScalar(1.))
{
        m_shapeType = TERRAIN_SHAPE_PROXYTYPE;

        btScalar        quantizationMargin = 1.f;

        //enlarge the AABB to avoid division by zero when initializing the quantization values
        btVector3 clampValue(quantizationMargin,quantizationMargin,quantizationMargin);

        btVector3       halfExtents(0,0,0);

        switch (m_upAxis)
        {
        case 0:
                {
                        halfExtents.setValue(
                                btScalar(m_maxHeight),
                                btScalar(m_width), //?? don't know if this should change
                                btScalar(m_length));
                        break;
                }
        case 1:
                {
                        halfExtents.setValue(
                                btScalar(m_width),
                                btScalar(m_maxHeight),
                                btScalar(m_length));
                        break;
                };
        case 2:
                {
                        halfExtents.setValue(
                                btScalar(m_width),
                                btScalar(m_length),
                                btScalar(m_maxHeight)
                        );
                        break;
                }
        default:
                {
                        //need to get valid m_upAxis
                        btAssert(0);
                }
        }

        halfExtents*= btScalar(0.5);
        
        m_localAabbMin = -halfExtents - clampValue;
        m_localAabbMax = halfExtents + clampValue;
        btVector3 aabbSize = m_localAabbMax - m_localAabbMin;

}


btHeightfieldTerrainShape::~btHeightfieldTerrainShape()
{
}



void btHeightfieldTerrainShape::getAabb(const btTransform& t,btVector3& aabbMin,btVector3& aabbMax) const
{
        btVector3 halfExtents = (m_localAabbMax-m_localAabbMin)* m_localScaling * btScalar(0.5);
        halfExtents += btVector3(getMargin(),getMargin(),getMargin());

        btMatrix3x3 abs_b = t.getBasis().absolute();  
        btPoint3 center = t.getOrigin();
        btVector3 extent = btVector3(abs_b[0].dot(halfExtents),
                   abs_b[1].dot(halfExtents),
                  abs_b[2].dot(halfExtents));
        

        aabbMin = center - extent;
        aabbMax = center + extent;


}

btScalar        btHeightfieldTerrainShape::getHeightFieldValue(int x,int y) const
{
        btScalar val = 0.f;
        if (m_useFloatData)
        {
                val = m_heightfieldDataFloat[(y*m_heightStickWidth)+x];
        } else
        {
                //assume unsigned short int
                unsigned char heightFieldValue = m_heightfieldDataUnsignedChar[(y*m_heightStickWidth)+x];
                val = heightFieldValue* (m_maxHeight/btScalar(65535));
        }
        return val;
}





void    btHeightfieldTerrainShape::getVertex(int x,int y,btVector3& vertex) const
{

        btAssert(x>=0);
        btAssert(y>=0);
        btAssert(x<m_heightStickWidth);
        btAssert(y<m_heightStickLength);


        btScalar        height = getHeightFieldValue(x,y);

        switch (m_upAxis)
        {
        case 0:
                {
                vertex.setValue(
                        height,
                        (-m_width/btScalar(2.0)) + x,
                        (-m_length/btScalar(2.0) ) + y
                        );
                        break;
                }
        case 1:
                {
                        vertex.setValue(
                        (-m_width/btScalar(2.0)) + x,
                        height,
                        (-m_length/btScalar(2.0)) + y
                        );
                        break;
                };
        case 2:
                {
                        vertex.setValue(
                        (-m_width/btScalar(2.0)) + x,
                        (-m_length/btScalar(2.0)) + y,
                        height
                        );
                        break;
                }
        default:
                {
                        //need to get valid m_upAxis
                        btAssert(0);
                }
        }

        vertex*=m_localScaling;
        
}


void btHeightfieldTerrainShape::quantizeWithClamp(int* out, const btVector3& point,int /*isMax*/) const
{
        btVector3 clampedPoint(point);
        clampedPoint.setMax(m_localAabbMin);
        clampedPoint.setMin(m_localAabbMax);

        btVector3 v = (clampedPoint);// - m_bvhAabbMin) * m_bvhQuantization;

        //TODO: optimization: check out how to removed this btFabs
                
        out[0] = (int)(v.getX() + v.getX() / btFabs(v.getX())* btScalar(0.5) );
        out[1] = (int)(v.getY() + v.getY() / btFabs(v.getY())* btScalar(0.5) );
        out[2] = (int)(v.getZ() + v.getZ() / btFabs(v.getZ())* btScalar(0.5) );
        
}


void    btHeightfieldTerrainShape::processAllTriangles(btTriangleCallback* callback,const btVector3& aabbMin,const btVector3& aabbMax) const
{
        (void)callback;
        (void)aabbMax;
        (void)aabbMin;

        //quantize the aabbMin and aabbMax, and adjust the start/end ranges

        int     quantizedAabbMin[3];
        int     quantizedAabbMax[3];

        btVector3       localAabbMin = aabbMin*btVector3(1.f/m_localScaling[0],1.f/m_localScaling[1],1.f/m_localScaling[2]);
        btVector3       localAabbMax = aabbMax*btVector3(1.f/m_localScaling[0],1.f/m_localScaling[1],1.f/m_localScaling[2]);
        
        quantizeWithClamp(quantizedAabbMin, localAabbMin,0);
        quantizeWithClamp(quantizedAabbMax, localAabbMax,1);
        
        

        int startX=0;
        int endX=m_heightStickWidth-1;
        int startJ=0;
        int endJ=m_heightStickLength-1;

        switch (m_upAxis)
        {
        case 0:
                {
                        quantizedAabbMin[1]+=m_heightStickWidth/2-1;
                        quantizedAabbMax[1]+=m_heightStickWidth/2+1;
                        quantizedAabbMin[2]+=m_heightStickLength/2-1;
                        quantizedAabbMax[2]+=m_heightStickLength/2+1;

                        if (quantizedAabbMin[1]>startX)
                                startX = quantizedAabbMin[1];
                        if (quantizedAabbMax[1]<endX)
                                endX = quantizedAabbMax[1];
                        if (quantizedAabbMin[2]>startJ)
                                startJ = quantizedAabbMin[2];
                        if (quantizedAabbMax[2]<endJ)
                                endJ = quantizedAabbMax[2];
                        break;
                }
        case 1:
                {
                        quantizedAabbMin[0]+=m_heightStickWidth/2-1;
                        quantizedAabbMax[0]+=m_heightStickWidth/2+1;
                        quantizedAabbMin[2]+=m_heightStickLength/2-1;
                        quantizedAabbMax[2]+=m_heightStickLength/2+1;

                        if (quantizedAabbMin[0]>startX)
                                startX = quantizedAabbMin[0];
                        if (quantizedAabbMax[0]<endX)
                                endX = quantizedAabbMax[0];
                        if (quantizedAabbMin[2]>startJ)
                                startJ = quantizedAabbMin[2];
                        if (quantizedAabbMax[2]<endJ)
                                endJ = quantizedAabbMax[2];
                        break;
                };
        case 2:
                {
                        quantizedAabbMin[0]+=m_heightStickWidth/2-1;
                        quantizedAabbMax[0]+=m_heightStickWidth/2+1;
                        quantizedAabbMin[1]+=m_heightStickLength/2-1;
                        quantizedAabbMax[1]+=m_heightStickLength/2+1;

                        if (quantizedAabbMin[0]>startX)
                                startX = quantizedAabbMin[0];
                        if (quantizedAabbMax[0]<endX)
                                endX = quantizedAabbMax[0];
                        if (quantizedAabbMin[1]>startJ)
                                startJ = quantizedAabbMin[1];
                        if (quantizedAabbMax[1]<endJ)
                                endJ = quantizedAabbMax[1];
                        break;
                }
        default:
                {
                        //need to get valid m_upAxis
                        btAssert(0);
                }
        }

        
  

        for(int j=startJ; j<endJ; j++)
        {
                for(int x=startX; x<endX; x++)
                {
                        btVector3 vertices[3];
                        if (m_flipQuadEdges || (m_useDiamondSubdivision && !((j+x) & 1)))
                        {
        //first triangle
        getVertex(x,j,vertices[0]);
        getVertex(x+1,j,vertices[1]);
        getVertex(x+1,j+1,vertices[2]);
        callback->processTriangle(vertices,x,j);
        //second triangle
        getVertex(x,j,vertices[0]);
        getVertex(x+1,j+1,vertices[1]);
        getVertex(x,j+1,vertices[2]);
        callback->processTriangle(vertices,x,j);                                
                        } else
                        {
        //first triangle
        getVertex(x,j,vertices[0]);
        getVertex(x,j+1,vertices[1]);
        getVertex(x+1,j,vertices[2]);
        callback->processTriangle(vertices,x,j);
        //second triangle
        getVertex(x+1,j,vertices[0]);
        getVertex(x,j+1,vertices[1]);
        getVertex(x+1,j+1,vertices[2]);
        callback->processTriangle(vertices,x,j);
                        }
                }
        }

        

}

void    btHeightfieldTerrainShape::calculateLocalInertia(btScalar ,btVector3& inertia) const
{
        //moving concave objects not supported
        
        inertia.setValue(btScalar(0.),btScalar(0.),btScalar(0.));
}

void    btHeightfieldTerrainShape::setLocalScaling(const btVector3& scaling)
{
        m_localScaling = scaling;
}
const btVector3& btHeightfieldTerrainShape::getLocalScaling() const
{
        return m_localScaling;
}