The simplified version of my question is: How can I create the blendmap texture, in code, so that I can pass that into my shader for multitexturing a terrain? Verbose version: I have a simple terrain (grid) with tiled textures. I have a shader that takes 4 textures and uses the rbga in the blendmap as weights when rendering the 4 tiled textures. I've always just fussed around in photoshop to make blendmaps, but now I want to be able to make them in my World Editor program. If a user selects a tile I want it to turn into the desired texture (grass, dirt, rock,etc..). Thanks in advance.