feature request model.voxel_plot

[shimwell]

Description

I have been using model.plot and geometry.plot for a while and was thinking it might be a good idea to add the equivalent functions for voxel plots. model.voxel_plot, geometry.voxel_plot, universe.voxel_plot cell.voxel_plot, region.voxel_plot.

One downside of this is that it would add about 400 lines of code to the repo

Alternatives

Continue to use the existing method, which requires an xml export and not particularly convenient for users as there is little automation.

my_geometry.export_to_xml()
vox_plot = openmc.VoxelPlot()
vox_plot.width = my_geometry.bounding_box.width
vox_plot.origin = my_geometry.bounding_box.center
vox_plot.pixels = [int(w* 0.1) for w in my_geometry.bounding_box.width]
vox_plot.color_by = 'material'
vox_plot.to_vtk(output='voxel_plot.vti')

Compatibility

compatibility would be fine, existing method would continue to work

[shimwell]

While looking through the code I notice that we make a voxel plot first as a h5 file and then convert to vti for viewing in paraview.

This can be two very large files if the resolution / pixel is high.

Ideally we would have a method a bit like model._id_map that can get the values and save straight to a paraview compatible file without having to do a convert. This would save time and disk space.