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btHeightfieldTerrainShape.cpp

/*
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)
: 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.))
{


      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()
{
}



00092 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;
}

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