Calculates a Delaunay Tetrahedralization of the 'positions' point set - the same way the lightmapper.
Tetrahedralizes the space for Light Probes. outIndices index into the array of outPositions and every four indices correspond to a tetrahedron. During the tetrahedralization any position duplicates withing some tolerance are removed (the first element is kept, subsequent are removed), so outPositions might have fewer elements than positions.