Does fvdb grids support tiles/background values?

[jdumas]

Hi,

I'm comparing the result of evaluating a VDB grid obtained by converting a mesh to SDF via openvdb::tools::meshToVolume. It seems that the results given by Grid.sample_trilinear() give incorrect values outside of the narrow-band, whereas openvdb::tools::BoxSampler::sample() correctly evaluate the sign and background distance outside of the narrow-band:

fVDB Sampling	OpenVDB Sampling

I don't see any notion of tile/background data in fVDB's documentation, so I imagine this data is lost when importing a volume from a NanoVDB grid?

[fwilliams]

Hey @jdumas thanks for flagging this - the sampling functions currently use a default 0.0 background value but it should be easy to add a background value as an argument to these.

We should also load the bg value in when importing a file.

We'll try to get to it as part of the next release or happy to help you contribute this if you need it sooner.

[jdumas]

I think it's more than a background value, you also need the per-tile values (the value for inside/outside is signed differently with OpenVDB).