I have a textured model for which I would like to apply an alpha mask - it can contain several materials with several textures. The textures were applied using a given UV projection, and the mask I created needs another UV projection/unwrapping.

Can you tell me how to tell Blender to mask the object material (make it transparent) where the mask says so (values in [0, 1]), even if it uses a different UV maps than the texture (I cannot therefore use an RGBA texture). The ideal solution would not use Nodes, or should be as cross-render compatible as possible (switching from Blender internal to Cycles should bring no additional steps to get the same alpha mask effect). I am definitely open to Python scripting (I'd like to implement this functionnality in a script).

Any hints appreciated, Thanks !


In Cycles render use a texture with a selected uv input to determine a [factor] value with a mix node. The mix node has two inputs with a transparent shader and diffuse shader.

In Blender render use the material texture with a given uv to affect [influence] alpha. The material alpha may need to be set to zero.

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  • $\begingroup$ Thanks for your answer, this is what I was thinking of. However, if there is a more cross-render compatible solution, I would appreciate it. The thing is that I am scripting this material alpha masking with Python, and I am already working on complex material Node trees. So I would love to find a way not to use nodes. $\endgroup$ – Jonathan Chemla Aug 26 '15 at 5:54

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