void btFluidHfBuoyantConvexShape::generateShape(btScalar collisionRadius, btScalar volumeEstimationRadius)
{
m_voxelPositions.resize(0);
btVoronoiSimplexSolver simplexSolver;
btTransform voxelTransform = btTransform::getIdentity();
btVector3 aabbMin, aabbMax;
getAabb( btTransform::getIdentity(), aabbMin, aabbMax ); //AABB of the convex shape
//Generate voxels for collision
{
btSphereShape collisionShape(collisionRadius);
const btScalar collisionDiameter = btScalar(2.0) * collisionRadius;
btVector3 numVoxels = (aabbMax - aabbMin) / collisionDiameter;
for(int i = 0; i < ceil( numVoxels.x() ); i++)
{
for(int j = 0; j < ceil( numVoxels.y() ); j++)
{
for(int k = 0; k < ceil( numVoxels.z() ); k++)
{
btVector3 voxelPosition = aabbMin + btVector3(i * collisionDiameter, j * collisionDiameter, k * collisionDiameter);
voxelTransform.setOrigin(voxelPosition);
if( intersect(&simplexSolver, btTransform::getIdentity(), voxelTransform, m_convexShape, &collisionShape) )
m_voxelPositions.push_back(voxelPosition);
}
}
}
const bool CENTER_VOXELS_AABB_ON_ORIGIN = true;
if(CENTER_VOXELS_AABB_ON_ORIGIN)
{
btVector3 diameter(collisionDiameter, collisionDiameter, collisionDiameter);
btVector3 voxelAabbMin(BT_LARGE_FLOAT, BT_LARGE_FLOAT, BT_LARGE_FLOAT);
btVector3 voxelAabbMax(-BT_LARGE_FLOAT, -BT_LARGE_FLOAT, -BT_LARGE_FLOAT);
for(int i = 0; i < m_voxelPositions.size(); ++i)
{
voxelAabbMin.setMin(m_voxelPositions[i] - diameter);
voxelAabbMax.setMax(m_voxelPositions[i] + diameter);
}
btVector3 offset = (voxelAabbMax - voxelAabbMin)*btScalar(0.5) - voxelAabbMax;
for(int i = 0; i < m_voxelPositions.size(); ++i) m_voxelPositions[i] += offset;
}
}
//Estimate volume with smaller spheres
btScalar estimatedVolume;
{
btSphereShape volumeEstimationShape(volumeEstimationRadius);
int numCollidingVoxels = 0;
const btScalar estimationDiameter = btScalar(2.0) * volumeEstimationRadius;
btVector3 numEstimationVoxels = (aabbMax - aabbMin) / estimationDiameter;
for(int i = 0; i < ceil( numEstimationVoxels.x() ); i++)
{
for(int j = 0; j < ceil( numEstimationVoxels.y() ); j++)
{
for(int k = 0; k < ceil( numEstimationVoxels.z() ); k++)
{
btVector3 voxelPosition = aabbMin + btVector3(i * estimationDiameter, j * estimationDiameter, k * estimationDiameter);
voxelTransform.setOrigin(voxelPosition);
if( intersect(&simplexSolver, btTransform::getIdentity(), voxelTransform, m_convexShape, &volumeEstimationShape) )
++numCollidingVoxels;
}
}
}
//Although the voxels are spherical, it is better to use the volume of a cube
//for volume estimation. Since convex shapes are completely solid and the voxels
//are generated by moving along a cubic lattice, using the volume of a sphere
//would result in gaps. Comparing the volume of a cube with edge length 2(8 m^3)
//and the volume of a sphere with diameter 2(~4 m^3), the estimated volume would
//be off by about 1/2.
btScalar volumePerEstimationVoxel = btPow( estimationDiameter, btScalar(3.0) );
//btScalar volumePerEstimationVoxel = btScalar(4.0/3.0) * SIMD_PI * btPow( volumeEstimationRadius, btScalar(3.0) );
estimatedVolume = static_cast<btScalar>(numCollidingVoxels) * volumePerEstimationVoxel;
}
m_volumePerVoxel = estimatedVolume / static_cast<btScalar>( getNumVoxels() );
m_totalVolume = estimatedVolume;
m_collisionRadius = collisionRadius;
}
// Returns the size (in bytes) of the data blob
int32_t RtExternalImageInfo::getDataSize() const {
return getBytesPerPix()*getNumVoxels();
}
