Add scattering model for shadow rays
This adds the possibility to blend between VTK's gradient-based shading method and a volumetric scattering model, which uses shadow rays, with a new parameter (replacing the boolean VolumetricShadow). It also adds volumetric anisotropy in vtkVolumeProperty, which is used by the anisotropy model. Little demo in paraview (the name and ranges of some parameters have been changed but the idea is here):
Edited by Gaspard Thevenon