Optimizing multiple shader effects

[clabe45]

Right now, rendering with a lot of shader effects can be slow. Each shader effect has to send the image as a uniform, run the GLSL shader, and then send the new image as a uniform for the next shader. This involves a lot of copying between the CPU and the GPU, which AFAIK can be expensive. I think we should find a way to either run all the effects for a single layer in one pass or avoid transferring the texture between the CPU and the GPU so much.

Reference:
vd.effect.Shader