How to use renderMeshFromViewpoint

I am struggling getting this to work, by work, I mean get anything drawn on the screen. I am currently using a MTKView to show the color camera, SCNView to show a cube and scan area as well as other things, and now I want to show the mesh.

What all needs to happen in OpenGL to get this to work? I am looking at the scanner app and have implemented all I think I need, but still nothing showing up. I am just layering the metal view, scene kit view and now the GLKView…is there a problem in doing this? Thanks in advance!

I am looking at the Scanner App and wondering if a custom shader is used when rendering the mesh while doing a scan? Or if the shaders in the CustomShaders.h file are only used for rendering the mesh after the scanning is complete and the software is just displaying what was captures?