Shader BGA about raindrop

[TomoAlien]

Basically, instead of using still pictures or images, it will allow people to use OpenGL Pixel Shaders as BGA.
This will allow for people with beefier GPUs to have high-quality resolution-independent background animations.

Obviously, this will require Fast Fourier Transforms to be implemented as to create visuals that respond properly to the audio. However, we'd need to know what kind of implementation to use.

Then there's the various variables that should be passed to the shader:
-Song Time - Time from beginning of the song
-Animation Time - Time from the shader being called via BGA change
-Current Song BPM
-Current Song Meter - Shouldn't be too hard, considering the value is already a float.

And maybe some for fun stuff:
-Combo Count
-Health Percentage
-Score Percentage
-Hit Accuracy Grade

[zardoru]

Might be important to add the aspect ratio.

[zardoru]

shader support is up. BGAs are still not up though.