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mattshort
11-22-2005, 02:43 PM
I've got an explosion with debris (created with hypervoxels) I want to comp into a scene with After Effects. How can I get shadows of the explosion & debris on the ground plane and render them out seperately for compositing? There is no object currently for the ground plane, I just set up a collision effector.

RussDude87
11-23-2005, 02:13 PM
It seems to me that the explotion itself would make light and therefore that part wouldn't cast a shadow, but for the debries... I beleive there is a save motion option under the particle options, you can do that for your objects, and then you can take your high-render time explotion out of the render. I'm not on a LW equiped computer or I'd find what I'm talking about. As for shadows, I'd just get a single poly plain texture it green for composite sake. Then I'd put a light (distant or a spot with a wide angle) at the same angle as your destination. Then when you bring it into After Effects there should be an option in there to hide green. This would cause your shadows to be cast, but the plain wouldn't show up.

Again, I can't test this here as I dont have those programs avilble right now, but that's the jist of it.

mattshort
11-24-2005, 05:04 AM
Thanks for the tip. I set up a ground plane object (green) and made that my collision object. I then made everything else unseen by camera to get a shadow pass on the green ground plane and keyed out the green in AE. Then I adjusted the shadows (opacity/blur/CC) to make the comp realistic.

lwaddict
12-15-2005, 08:05 AM
Whew...that's a lot of work.

Did ya try just setting up some planes as shadowcatchers with the diffusion affecting the alpha channel and saving that sequence?

I might be working this wrong, not in front of my PC, but I've always had it done this way and the comps come out great with no chroma keying necessary.

Just my two cents.

mattshort
12-18-2005, 02:42 PM
Whew...that's a lot of work.

Did ya try just setting up some planes as shadowcatchers with the diffusion affecting the alpha channel and saving that sequence?

What's the recipe for that? That's what I was trying to figure out. I'm using 7.5.

lwaddict
12-18-2005, 05:04 PM
In the Surface Editor, for the plane that you plan to use to catch the shadows...
go to the Advanced panel and set the Alpha Channel for Shadow Density.

Make sure to either render the sequence out as either a 32 bit TGA or a pair of files, JPG and Alpha JPG for example.

Try it. BAM. Nice compositing piece eh?

jeremyhardin
12-18-2005, 06:19 PM
you can also have a light that just cast's shadows, but doesn't add to the brightness of things. a negative light with a black color and white shadows do this. here's a plugin that automates it:
http://jeremy.lwidof.net/lscript/#shadow_lights

mattshort
12-21-2005, 02:45 AM
In the Surface Editor, for the plane that you plan to use to catch the shadows...
go to the Advanced panel and set the Alpha Channel for Shadow Density.

Make sure to either render the sequence out as either a 32 bit TGA or a pair of files, JPG and Alpha JPG for example.

Try it. BAM. Nice compositing piece eh?
Thats what I was looking for, thanks!