Day 134: Background Color

Today I noticed that the engine was lacking an obvious feature, the ability to have a background color instead of a skybox, so I added this functionality to the camera class, and now it's up to the user to decide which one to use.

Then I fixed a nasty bug that was giving problems to the particle emitters. It took me a very long time to fix, and even now I'm not sure why it was behaving like that. The error was a stupid variable not initialized to zero, and in release mode this created tons of problems.