I am new to Houdini, and primarily have worked on Maya. In my transition 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 some bunch of geometry copyed to a popnet. I also added a light source which doesnt light all of the seperate 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 pixels.

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

The alpha channel will be present for your objects even if they are in complete darkness, that is how an alpha channel works. Perhaps you should use a luminance key in your compositing network, rather than the alpha