We are evaluating a variety of different graphic engines for use in our game and we want to be able to use 2 different textures for many of our sprite maps. One sprite map would be the standard RGBA values and the other sprite map would contain normal data for these sprites. To be clear, these are not 3D models. The normal map would just help the flat 2D sprites better react to lighting.
I've done this exact thing in OpenGL ES 2.0 and I imagine the shader code would work in Cocos2D, but I'm wondering how I go about doing this in Cocos2D? I know you can assign shaders to sprites, but how would I specify a secondary texture?