@Chris_Rorden
We are definitely not trying to load 16K^3 datasets. MOst of our datasets are around 3-5 gigavoxels. This particular one is 2560x2560x676.
Issue might be relating to VTK reporting the MAX_3D_TEXTURE as erroneously as 2K, as shown in the error message:
ERROR: OpenGL MAX_3D_TEXTURE_SIZE is 2048
Invalid texture dimensions [2560, 2560, 676]
This error is consistent for same dataset rendered with GPU rendering both under Slicer and Paraview (5.6.0).