I was going to draw my shadow map into one channel of a 16 bit texture and then draw a different shadow map into another channel of the same texture.
I realized that this might not be possible to do efficiently since my targetted hardware (Xbox) does not support blending R16G16 formats. (Although the HDRBlendable might make it possible if I need a blendable format to do this.)
Is it possible to mask one channel of a R16G16 texture on the Xbox? How do I do that?