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monovich
09-22-2006, 04:31 AM
I've run into a few problems compositing in AE in 32bit tonight and I'm not sure how to fix my problems so I thought I'd post here. I'm going to be integrating some 3d objects onto tracked plates and want to match the lighting.

Right now I've just rendered two passes and I realize that moving forward I'll probably need a few more, and if you have any advice here it'd be appreciated. I'm rendering out each pass as a seperate 32bit EXR file.

Ok, problem #1:

I rendered out a basic "shadow" pass (which really includes occlusion and the shadow right now). Normally with a shadow layer you can just hit the Multiply layer mode over the layer under it and the darks will darken and the lights will drop out. When you are in 32bit linear color space in AE, using the Multiply layer mode the darks appear to darken and the lights appear to lighten the layers below. With the HDR data in the EXR they seem to lighten the layer below that much more (because the whites are "bright"?). My question is - how do I get my shadow pass to darken like a normal shadow pass?
Did all of that make sense? Do I have the concept wrong all together?

problem #2:

With my EXR layer of the trucks comped in over the top of the background layers, I'm getting a small white halo around certain areas where the layers intersect (see example). This doesn't happen over an empty background, where it looks fine, only when it's laid over the top of other footage. I'm not really sure why this is. The footage was rendered over black with the black premultiplied out in the interpret dialogue box.

This is really the first time I've tried comping with 32bit layers in After Effects linear color space, and it's a bit confusing. Any help would be appreciated.

I know AE isn't a huge compositing package, but I don't have the time to learn another package right now.

thanks.

-sf
Mylenium
09-22-2006, 05:51 AM
Ok, problem #1:

I rendered out a basic "shadow" pass (which really includes occlusion and the shadow right now). Normally with a shadow layer you can just hit the Multiply layer mode over the layer under it and the darks will darken and the lights will drop out. When you are in 32bit linear color space in AE, using the Multiply layer mode the darks appear to darken and the lights appear to lighten the layers below. With the HDR data in the EXR they seem to lighten the layer below that much more (because the whites are "bright"?). My question is - how do I get my shadow pass to darken like a normal shadow pass?
Did all of that make sense? Do I have the concept wrong all together?

This is a common problem. Like Cineon, EXRs use logarithmic scales and store much more info in the bright areas. There is a special highlight adjustment effect somewhere (sorry, not in front of AE ATM, so I don't know the exact name and location, but I think it's under Utilities). You could also use the Color Profile Converter effect to limit the dynamic range and match it up with the range of your footage.


problem #2:

With my EXR layer of the trucks comped in over the top of the background layers, I'm getting a small white halo around certain areas where the layers intersect (see example). This doesn't happen over an empty background, where it looks fine, only when it's laid over the top of other footage. I'm not really sure why this is. The footage was rendered over black with the black premultiplied out in the interpret dialogue box.

This is really the first time I've tried comping with 32bit layers in After Effects linear color space, and it's a bit confusing. Any help would be appreciated.
-sf

Similar to the first problem, AE will "blow up" all effects to the full 32 bpc range when you work in that mode. This means it will produce overbright pixels when layers add up. You should use the tools mentioned above again or properly convert the color space by using the Compander effect (it will auto-compensate) on your background plate.

Mylenium
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09-22-2006, 05:51 AM
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