Invisible matte object (well sort-of)

[Tim Saunders]

Sorry for the duplicate post, but I thought I would put this in the v-ray section as well, since I might be able to accomplish it based on v-ray settings.

 

I'm wondering if anyone know how I can achieve this.

 

I am hoping to animate a space developing from the ground-up. I thought i would be able to place a large box over the space that was invisible. The box could mask everything it over-laps, but as the box is moved up, you could see everything beneath it. The problem is, I want to see this happen from a view above the space, similar to the second image.

 

The images below are obviously not the actual model, I just wanted to create some test. But I can't seem to make the box mask the objects it covers (physically), but still allow the camera to see the objects it is not physically covering. Obviously, once an objects has a matte/mask property, if it blocks the view of things behind it, they will be masked.

 

Does this make sense at all?

 

I guess another way to describe it would be like animated clipping planes. But only, the clip will be done on the scene's Z-axis, not the camera's.

 

Any ideas?

 

[dean@pikcells]

so am i right in thinking that you want everything inside the box to be invisible to the camera, and everything else visable?

[Tim Saunders]

Yes. that's why I added the "well sort-of" to the title. Because in the true sense, the object is not a typical matte object, because it would still allow objects behind it to be seen.