Function SampleMesh

extensions/flexExtSoft.cpp:394–504

creates mesh interior and surface sample points and clusters them into particles

// creates mesh interior and surface sample points and clusters them into particles
void SampleMesh(const Vec3* vertices, int numVertices, const int* indices, int numIndices, float radius, float volumeSampling, float surfaceSampling, std::vector<Vec3>& outPositions)
{
	Vec3 meshLower(FLT_MAX);
	Vec3 meshUpper(-FLT_MAX);

	for (int i = 0; i < numVertices; ++i)
	{
		meshLower = Min(meshLower, vertices[i]);
		meshUpper = Max(meshUpper, vertices[i]);
	}

	std::vector<Vec3> samples;

	if (volumeSampling > 0.0f)
	{
		// recompute expanded edges
		Vec3 edges = meshUpper - meshLower;

		// use a higher resolution voxelization as a basis for the particle decomposition
		float spacing = radius / volumeSampling;

		// tweak spacing to avoid edge cases for particles laying on the boundary
		// just covers the case where an edge is a whole multiple of the spacing.
		float spacingEps = spacing*(1.0f - 1e-4f);

		// make sure to have at least one particle in each dimension
		int dx, dy, dz;
		dx = spacing > edges.x ? 1 : int(edges.x / spacingEps);
		dy = spacing > edges.y ? 1 : int(edges.y / spacingEps);
		dz = spacing > edges.z ? 1 : int(edges.z / spacingEps);

		int maxDim = max(max(dx, dy), dz);

		// expand border by two voxels to ensure adequate sampling at edges
		meshLower -= 2.0f*Vec3(spacing);
		meshUpper += 2.0f*Vec3(spacing);
		maxDim += 4;

		vector<uint32_t> voxels(maxDim*maxDim*maxDim);

		// we shift the voxelization bounds so that the voxel centers
		// lie symmetrically to the center of the object. this reduces the 
		// chance of missing features, and also better aligns the particles
		// with the mesh
		Vec3 meshOffset;
		meshOffset.x = 0.5f * (spacing - (edges.x - (dx - 1)*spacing));
		meshOffset.y = 0.5f * (spacing - (edges.y - (dy - 1)*spacing));
		meshOffset.z = 0.5f * (spacing - (edges.z - (dz - 1)*spacing));
		meshLower -= meshOffset;

		Voxelize((const float*)vertices, numVertices, indices, numIndices, maxDim, maxDim, maxDim, &voxels[0], meshLower, meshLower + Vec3(maxDim*spacing));

		// sample interior
		for (int x = 0; x < maxDim; ++x)
		{
			for (int y = 0; y < maxDim; ++y)
			{
				for (int z = 0; z < maxDim; ++z)