XM Magdalena 3D print, GGeorgy (3D)
LC #42 Pipers Alley

View Full Version : Shadow composite problem.

02-20-2003, 05:42 AM
I'm very sorry for even asking this, because I'm sure the answer has to be on the forums here somewhere, I just can't seem to find it, and I'm in somewhat of a time crunch, here.
Alright, I'm using buffer export to export my shadows to file. It's groovy. I got that. Problem is this: i have stand-in geometry that's recieving my shadows that I'm compositing into live-action film. My shadows are all fine, but my geometry is being anti-aliased against the stand-in geometry...which is very bad. In other words, when I bring in the moving geometry, I have really cool white halo's around it where it's been AA'd against the white geometry in the scene instead of nothing.

I hope that made sense. =)
Any ideas, d00ds?

I'd really hate to have to render this all twice. =)

Mike RB
02-20-2003, 06:26 AM
Make sure you set the surface properties of the stand-in object 's alpha value in the advanced tab to shadow.

02-20-2003, 06:31 AM
Yep, it's set to shadow density. But, for some reason, if you watch it render in the previewer as it goes through the frames, it renders WITH the stand-in geometry in there, even though it's only supposed to recieve shadows as alpha density. =P It doesn't show up in the final render, but you can tell it's been anti-aliased against it. It's weird as hell.

Mike RB
02-20-2003, 06:44 AM
use the matte color option in the object render properties and set it to the same as your background color.


02-20-2003, 06:49 AM
It's too bad I can't have a "matte image" instead of "matte color" =)

Mike RB
02-20-2003, 06:57 AM
dont render with your image in the bkg, render on black or whatever and them together in post.

02-20-2003, 07:00 AM
Yeah, i know this, but I dislike matting it against black. It makes it seem almost outlined sometimes...like if the composited object goes against something white, for instance. That's just me being anal, though. Black is 99.9% unnoticeable. I should just stick with that.

Thanks for your help, Mike.

Mike RB
02-20-2003, 07:06 AM
if you background is going to be green, use that, whatever will be the least noticable.


02-20-2003, 07:08 AM
The part that sucks is that it travels between several things in the background. Some light, some very dark. Yehaa for fun post. =)

02-20-2003, 10:27 AM
you could use a matte controll in composite afterwards. donīt know wich tool you use but I know that most apps like combustion or AE have a funktion where you can postprocess the matte with shrink, blurr to avoid the typical outline effect that happens when you have a cg element with alpha. as alphas are not antialiased they are not as acurate when you render with AA.

02-20-2003, 11:54 AM
Can't you map the background image onto the standin images as a front projection so they will completely blend in with the background?

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