Refactor rendering code to be more extendable, and better performant. about openrhythm

[mdsitton]

Changed the name of the issue, because the goal atm isn't really multiple backends. The goal is efficient rendering with opengl.

My current plans with this are to implement a SceneGraph which will be linked with some kind of Spatial Partitioning likely a QuadTree. The QuadTree will be used to do Frustum Culling for SceneGraph objects. This will get us a smaller list of objects which can be more easily sorted by the object state (Shader, texture, etc). This will reduce state changes and allow us to batch together objects of the same type to reduce api overhead.

I'm not sure yet, but if we use instanced rendering for stuff we can do Frustum Culling within a Geometry Shader to improve performance under certain circumstances.

[mdsitton]

I have been working on getting the back-end rendering infrastructure setup for this, and also trying to get the renderer more ready for 3d in the near future. Basic triangle batching is working however currently the texture code is kind of bad, so i'm working on cleaning that up still. Once the texture code is fixed I will be trying out Texture Buffer Objects for supplying mesh transform matrices to the shaders because not all hardware supports the sizes that will be needed for uniforms/UBO's.

[mdsitton]

I've basically got this to the point where it is fairly usable, and we are infact rendering 3D now. Closing