SPIKE: Renderer optimizations

1. Cull objects that are behind others
2. See the renderer implementation here (do this for all meshes):
https://github.com/dotnet/Silk.NET/blob/main/examples/CSharp/OpenGL%20Tutorials/Tutorial%204.1%20-%20Model%20Loading/Program.cs

See if there are calls that are run multiple times a frame but could be run only once.

Camera's should have a cone like collider whose lenght is defined as the render distance.
When objects are outisde of that cone, they are culled and not rendered.

https://docs.unity3d.com/510/Documentation/Manual/OcclusionCulling.html
https://en.wikipedia.org/wiki/Potentially_visible_set