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Rhothgar
07-26-2007, 08:53 PM
Please if anyone knows why this is happening I could really use some help.

I have not gotten an answer from tech support....

Please take a look at the attachments....

Why are the hypervoxels picking up the RGB from objects that should not be showing up? :bangwall:

Dodgy
07-27-2007, 03:24 AM
Because they are semi transparent. What you want to do is render them over a black background and then use A holdback matte technique.

http://www.digitalartform.com/archives/2005/10/compositing_pre.html

What you really should be doing is colour keying the male character over the render, so you don't actually use the alpha of the render at all. Ie removing the Blue and placing her over the rendered frame as it is.

Rhothgar
07-27-2007, 05:18 PM
Because they are semi transparent. What you want to do is render them over a black background and then use A holdback matte technique.

http://www.digitalartform.com/archives/2005/10/compositing_pre.html

What you really should be doing is colour keying the male character over the render, so you don't actually use the alpha of the render at all. Ie removing the Blue and placing her over the rendered frame as it is.

Thanks for your response Dodgy. I really appreciate your help. :) Please keep in mind the problem is not the compositing but getting a clean alpha for the hypervoxels...in the final comp the blue screen will be keyed out and the live action character will be the top layer so the skeleton will not over lap etc.

I noticed this problem while basically setting up the rough shot (almost like an animatic) just to get a better idea of how the final shot will look (there are several other layers not shown) normally I would be rendering with a black background but since a sky dome is used for lighting with radiosity and "unseen by camera" does not seem to work in 9.0 I had to set the sky dome alpha to constant black... but as you can see in the alpha pic that seemed to work for every thing else BUT the hypervoxels.....:foreheads I have to drop a clean background in anyway so rendering both the RGB and Alpha is a must regardless...I wonder if all of this will be a non issue once I can use 9.2 I hope so. Thanks again for your reply!

Rhothgar
07-27-2007, 05:48 PM
Because they are semi transparent. What you want to do is render them over a black background and then use A holdback matte technique.

http://www.digitalartform.com/archives/2005/10/compositing_pre.html

What you really should be doing is colour keying the male character over the render, so you don't actually use the alpha of the render at all. Ie removing the Blue and placing her over the rendered frame as it is.

I just did a test.

Basically I took the skydome and ground plane out and rendered against a black background. this time the dust is perfect. Thanks!

so what I'll do is just render the skeletons in one layer with the skydome and radiosity then render the hypervoxels in a separate layer against a black background....glad the comp guys are doing the final comp and not me.

Thanks again for your help.

Maxx
07-29-2007, 10:43 AM
Isn't there a trick where you can set up your HDRI image with ImageWorld, then put a black image as the background image in the Composition tab and the render will use the lighting info from the HDRI but render the black background? I can't remember if that's it exactly, but I seem to remember a thread on just this issue either here or at spinquad. This sounds like it could save you some time, Rhothgar.

Rhothgar
08-01-2007, 09:48 PM
Isn't there a trick where you can set up your HDRI image with ImageWorld, then put a black image as the background image in the Composition tab and the render will use the lighting info from the HDRI but render the black background? I can't remember if that's it exactly, but I seem to remember a thread on just this issue either here or at spinquad. This sounds like it could save you some time, Rhothgar.

Maxx,

Thanks for the comments. I can't say that I've heard of that trick but its sounds like something I really need to check into...Thanks for mentioning it. The frustrating thing is that in LW8.5 all I had to do was go to object properties (for the skydome object) to the render tab and check unseen by camera. The radiosity information from the skydome would still be present AND I'd get a black background. Was just too easy and cool not to do it that way. It even worked in LW6.5. So I was quite surprised to see that it does not work in 9.0 but I have heard it does work in 9.2.... now I wonder if that is true....