So basically what I am trying to do is simple in concept but difficult to probably actually do with Blender. I have rendered a basic scene with just a flag(cloth physics) blowing in the wind(force field). I have UV unwrapped and applied a material and texture. What I wanted to know was whether you could somehow speed up the next render of the scene if only the texture image was changed? The idea is that people will design their own flag in a 2d image which then I put into a 3d scene for them to see it in ‘real life’
UV Pass is good in some cases, but sometimes it’s better to render shadeless colors (emission shader with your texture plugged into it) in a separate render. It will be rendering in no time, but will surely give better results than using UV Pass distortion.
Then use this render as your diffuse color when you combine the passes.