I see, so setting all data points in a regular grid beforehand would not really make sense. Not sure about sparse voxel octrees, not my area of epxertise; maybe vtkImplicitVolume is something for you? It’s a volume that’s specified through a function computing its points as far as I can tell from a quick glance the docs… not sure how this determines at which positions it evaluates the function though, or whether it provides a kind of level-of-detail functionality, as you probably require, out-of-the-box…