Rendering a correct Alpha

[afx]

I am dealing with some primitive rendering issues.

I have rendered out an image with an incorrect alpha and cant seem to fix it.

I have a scene with geometry copied to a popnet. I also added a light source which doesn't light all of the separate geometry, but a few of the ones within the lights gradient.

My issue is that the alpha has all of the geometry within it, and within compositing the un-light geometry is exposed as black, rather then not being there at all.

What the alpha should look like is dependent on what the light is cast upon and not all of the geo as a whole.

I am using a VEX super material and was wonder if there was a way to grab the rgb only for the alpha channel??

[afx]

Here is what i mean visually

Could this be because I am saving the frame out of mplay??

[SpencerL]

Here is what i mean visually

Could this be because I am saving the frame out of mplay??

It sounds like you want to use the luminence of your object as the alpha. If thats the case then a simple way of doing it is to just take the saturation down to 0 and reorder your image so either the R, G or B channel is set to your Alpha channel.

[afx]

Is there a way to do this in the VEX Super Material or should I take care of this issue in Compositing??

[DaJuice]

Hi Angelo, do you absolutely need to use the VEX Supermaterial? It's a bit old and there's no VOP network to play with. If you use the newer shaders in the Material Palette they all have VOP networks and it's very easy to add this effect using the TwoTone VOP. It provides basic toon-shading, and if we plug it into the alpha it will hide the parts that are not lit.

That's just one way to do it, I'm sure there are other methods.