Is there a way to composite out the object and only show its composited effect?

I have an object that I want to make a Glow effect, a volcano, but I do not want to see the Emitter plan in Cycles, just the glow effect from the Blur.

The Problem I have is when I alpha it back to the scene, the plan I use as the Emitter that is normally inside the volcano and hidden from view is now on the outside, not sure how to fix that.

Turning the camera off in Ray Visibility removes it from the compositor Render Layer, and I have no idea how to mask out the plan, since all I want is the blur effect it makes and not the object.

Update: There are a few issues with how this is done the right way, but just adding in a Color -> Z Combine fix my issue.

Sounds like you need to use the volcano as a Mask Layer.


Have the volcano on its own layer. In the Render Layer for the glow plane, select the layer for the volcano in the Mask Layer section.

Steve S

Thanks, but that’s not it, after playing with it a few hours, I found out the Z order is wrong, but my setup is complex, I am mixing Cycles and Internals in the same file, and even trying to composite in another scene, plus this layer is in Cycles, and I do not see any Z order includes, so I have no idea how to fix this, and searching the internet all night did not improve that, it seems masking the layer only remove it from the scene, since all scenes are composited, they do not show up on any layer you can mask this way.

One though is to figure out how to fix the z index, so its inside the volcano where it will be hid, I also have another object hidden from another object on that layer, so this I have to fix, so maybe I will work on that tomorrow, today was a wash, but thanks for the help, it gave me hope for a little while.