How do I use the alpha channel of a texture for arbitrary data in Cycles? I'm trying to use the alpha channel of an image as my emission map in cycles, but for some reason, the render just renders the alpha and not the colour of the texture, even when I plug only the colour directly into the diffuse BSDF and the diffuse directly into the output node. I'm actually trying to mix the diffuse with an emission shader to make certain parts of the texture always illuminated. However, with this setup, the alpha channel renders on top of itself and looks pretty much the same as when just plugging the alpha channel directly into the output via a diffuse shader.

Note that my image is in TGA format, after I originally had issues with using alpha on a PSD (which would always render white).

Here is my node setup:
In order to do what you are you describing, you need to make a couple changes to your node setup.


Change the Mix Shader to an Add Shader.
Unplug the texture color from the multiply node and plug the multiply node into the Strength instead of the Color of the Emission shader.  You can now use the multiply node to adjust the strength of the emissive parts of the material.