Layered Shader [Update]

This post is in addition to my Layering Shaders with Mental Ray post and the focus of that was the mib_color_mix node. A thread on SimplyMaya reminded me that I needed to update this thing.

I found that plugging bare textures into mib_color_mix slots results in weirdo alpha channels in the rendered image, like a strange masking effect on the shader.

This confused me for a while, it seems that Mental Ray uses the top most layer on the mib_color_mix to generate the alpha channel, which in this case is a simple fractal texture. It ignored the fact that there are solid SSS and mia_material shaders beneath it.

I needed to have my fractal spit out a solid alpha, and this is where the "alpha offset" attribute comes into play.

Alpha offset allows me to add black or white value to my texture's alpha in a uniform manner. I set the value to 1. The rendered image will look the same but my little torus will be solid in my alpha mask now because my fractal's alpha is all white.

And of course a value of -1 will have my fractal not even show up in the alpha channel of my render, since since its now black.

Commentor JJJenkins was having problems with alpha offset affecting his color channel and these are the results of my tests.  Forgive my texture, it's the result of 10 seconds in Photoshop lol.