I'm playing around with a RenderTexture and NGUI for some full-screen post processing and noticed that all of the shaders are setting ColorMask to RGB. (Inconvenient for me, because I want alpha values written out when rendering to a texture.) Is there any specific reason for this, other than that alpha isn't really needed when rendering to the screen? It looks like everything still works fine if I change it to RGBA, but I haven't tested thoroughly. Am I better off using a replacement shader when rendering to a texture?