3D visualization using pyvista

[mountaindust]

pyvista looks REALLY good for bringing VTK 3D visualization into Python in a manner that can actually be understood by a human. It even does mp4 rendering!

[mountaindust]

We will need to totally replace the current 3D interface. Here's what I'm imagining:

• Plot the agent locations (of course). Ghosting can be used for agents outside the domain
• Include text with basic information, like what we have now
• Include any immersed mesh structures and porous layers, like what we have now
• Instead of current kernel density estimation plots, include 2D projections of the KDE on three sides of the domain as psuedocolor meshes
• Try adding vorticity magnitude in 3D, but everything below a certain percent threshold value is transparent...? pyvista can compute the field gradients very efficiently through VTK. Or maybe some slices of arrows.