I have been fooling around with this today, without success. The idea started with me wanting to make a simple smoke swirl go through a light and then register on the surface below.
It has evolved into the same idea going through a spotlight with halo on.
I have everything working like I want, except I cannot seem to make an object transparent to the halo itself.
The object set on the left is a simple spotlight, halo step set to maximum. There is a cloud texture mapped to the light. The object set on the right is the same thing with the introduction of a simple plane. This plane I currently have set as Alpha zero, and the same texture as the spotlight assigned to the plane so that the “assigned texture affects alpha value” set on.
What I was hoping for was the swirl in the plane, would mask out the light and halo going down to the sphere, resulting in that nice shadow effect on the left. And allowing me to animate the texture on the plane to make it look like a layer of hazy smoke drifting through the light.
Anyway, with that said… is it even possible for the halo to pass through a transparent object? If so, how to do you set the tranparency to do it?