[BUG] Square/Planar Artifacts While Volume Rendering NVDB Files Using Optix about openvdb

[KaavayGupta]

After alot tinkering around, I've finally figured out the solution.
The problem was in example code provided by OptiX. It was accessing the volume coordinates in the raymarching loop.

In the function template<typename AccT> inline __device__ float transmittanceHDDA(const nanovdb::Vec3f& start, const nanovdb::Vec3f& end, AccT& acc, const float opacity ):

It used ijk = hdda.voxel() to get the current coordinate.
Replacing it to ijk = nanovdb::RoundDown<nanovdb::Coord>(ray(hdda.time() + 1.0001f)); solved this issue.

Though, I still cannot figure out the exact reason why this solved it.

Thanks!