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bgolden
06-25-2007, 05:11 PM
I have an animation of a marketplace where I want to isolate the trees from the rest of the animation so I can adjust their opacity in After Effects but unsure how to go about this.

Depending on where the camera is, sometimes the trees are in plane view and other times, they are partially behind buildings, light poles, etc. I've read various threads about miltipass, buffer export, etc., but still unclear how to A) only render the shadows of the trees [including any alphas in case items appear in front of the shadow and B) only render the trees in the same way where they have alphas that cut them off to appear behind or in front of other objects.

I've rendered out the animation without the trees, but now want to do a 'shadow pass' and then do a pass with the trees only - with none of the other items showing but the alphas of the other items included to clip the trees depending if something is in front of or behind the trees.

Lightwolf
06-25-2007, 05:17 PM
The trees pass you'd render out with all objects (except the trees) set as matte objects (black), alpha to 0. (object properties).

For the shadow pass you could try to see the trees to be unseen by camera, set all other objects to matte black, alpha channel to "use surface settings" and on all surfaces set Advanced->Alpha Channel->Shadow Density (make sure you save those objects with a different filename, just in case, mainly if you need the alpha channel of your main render without the trees).

Also, render tests to see if the passes contain what you need.

Cheers,
Mike

bgolden
06-25-2007, 06:47 PM
Mike to the rescue again. OK . . . I've started experimenting with the tree pass per your advice and it works like I want it to in the native renderer, but the alpha doesn't match up as I rendered the base frames in fPrime. When I try to output a test frame - the foreground elements come out black and no alpha appears to knock it out. I've tried with and without alpha on the render settings for fPrime, but no luck with either. Any ideas? Thanks again for the help Mike.

- Brad

Lightwolf
06-26-2007, 01:50 AM
Hm, I'm not sure if FPrime works properly with those options, I never tried it (we have a small render farm).

Sorry, I'm out of ideas then...

Cheers,
Mike

bgolden
06-27-2007, 10:18 AM
Some further research and it seems there is an issue with matching up LW alphas with fPrime. Trying to research and find out more and in the meantime, trying to find workarounds in After Effects with motion blur, choking, etc. Anyone else with info on this? Thanks.

Lightwolf
06-27-2007, 11:14 AM
Are you rendering with motion blur? As well as LW9.2?

Try making the motion blur a negative value in LW for the LW renders. Since 9.0 (I think) LW computes the motion blur in a different direction. It used to be from the current frame backwards in time, now it is forwards in time.

Cheers,
Mike

bgolden
06-27-2007, 11:28 PM
Hmmm. I'll give that a try and post the results.