Geometry masking. Is it possible?

[brewster]

Jusr reposting an earlier question which I still can't figure out the answer to...

Is there a way to render particles (or anything) so that only what is visible from the camera view is included in the rendered images? I keep getting ALL my particles when I try to composite the two layers in After Effects, and I just want the ones that are visible in that frame. Can I use the visible geometry to mask out the particles that shouldn't be visible? Any suggestions would be much appreciated. I've been hunting through the on-line help for days, and my eyes hurt... : )

[empleh]

If you are using the hardware render buffer there is a check box that will mask out geometry. It is under the render modes of the hardware render attribute editor.

If you are using software rendered particles you can assign all of the geometry in the scene a "background" shader so that the particles will be occluded and the geometry will be invisible.

Does this help?

ww

[brewster]

Thanks for the reply. I am not sure whether to use HW or SW rendering. I have instance replaced Point particles with simple geometry, so the actual particles are not being rendered, just the instanced stuff. Dows the HW buffer handle this?

Thanks!

[empleh]

In that case I would probably use software rendering and a background shader on the objects in the scene that sometimes occlude the particles. I think this will work like you want it to.

I don't think that you can select what geometry renders and what doesn't in the hardware render buffer, but I'm not sure and I don't have time to investigate right now. :-(.

There might be a better way but at this time I can't think of it.

good luck,
ww

[joojaa]

You can controll it its just like the viewport everthing thats hidden is hidden in hw... And if you instance and want them hw rendered without the particles then just make the particle object 100% transparent!

same applies to drawing override!

[brewster]

Help! None of this is solving my problem! I want the geometry to act as a mask in the render, yet NOT be included in the alpha channel. In other words, I only want the instanced particles to exist in the alpha channel, yet be occluded by the other geometry when they are not visible in any given frame! Anyone?! Please!Arghh!

Brewster

[empleh]

Did you try using the background shader on the geometry in the scene? Not the particles but the occluding geometry. It works for me when software rendering.

ww

[brewster]

I'll try that now, but won't it still render the background shader in the alpha channel?

[empleh]

For me the background shader doesn't leave an impression in the alpha. You can do a quick test with two spheres. Partially occlude one sphere with another that has a background shader and look at the alpha and see what it looks like.

Good luck,
ww

[brewster]

You're right - it seems to work beautifully. I just got overwhelmed by all the options, due to the fact that I am trying to use Render Layers as well as learn this other stuff at the same time. Thanks for the help!

Brewster