Is there a way to do this?

[timmatron]

Ok, so for our next animation we want to have some moving 3d people, which we've never done before. I want to composite them in seperately so we don't have to calc. gi on every frame for the whole thing.

But my question is: Is there any way to isolate a shadow cast per object? In this test, the box would represent something like a building, in which the shadow would be present in the main animation. But then when I do the people shadow pass, I would like to retain only the shadows of the people, but still have the alpha be cut off where the people shadows meet the model shadows. See my example below.





I know there is the tutorial Vlado put together on compositing, but it looks like a little more work than I want to do, and honestly, I don't totally understand how to make it work yet. What does everybody else usually do for animated 3d people, shadows, etc?

Thanks

[Morbid Angel]

well your thinking is not im the right track a bit. If you want to composite things, then you need to separate things for control. What you need to do is to render all shadows as a separate pass. Then you will have individual control over the shadow of the building and the cheracter, which you can use to cut out one from another or whatever. If I understood correctly, if you only want cheracter shadows but not building shadow, you can select the building and uncheck cast shadows. This will produce only cheracterts shadow.
So for example to minimize the amount of work, you can render your main pass with the building and the shadow, then render the cheracter shadow and the building shadow on its own.
That would be more or less simple. But I would render everything per pass, like raw gi, rgb, spec, reflection and so on then composite all of those together. Its a good idea, because if you render building shadow embedded into the color pass then you have no control over it post.
Have fun.

[timmatron]

Thanks. I would like to get to the point where I can composite all the elements together in Combustion, but I don't think my skill level is quite up to that point yet. Can't wait for the output to Combustion workspace in 1.5 But maybe I will give it a shot. Are there any Vray/Combustion specific tutorials I can reference that anybody knows of?

But at least I think we may do what you mentioned, and render the building shadow pass, and people shadow pass seperately, and then just subtract the building shadows from the people. I suppose that would work for now.

[panthon]

I have faced the same problem with no quick solution but manually masking shadow passes. There was a -rather complicated- tutorial about spherefade thingies in the official help but I havent even bothered to try. I dont use vray shadow pass, but maybe that's a thing u could look into, using it as a mask with multiply blending mode...

I am not sure about 1.5 exporting combustion workspaces. As far as i know, even if it creates a *.cws file, layers will not be ordered correctly, just dropped there for you to do the hard work.

[timmatron]

I am not sure about 1.5 exporting combustion workspaces. As far as i know, even if it creates a *.cws file, layers will not be ordered correctly, just dropped there for you to do the hard work.

Aww that sucks! Well, better than nothing I guess, but I was hoping it be as well integrated with Combustion as standard elements are.

[dlparisi]

Since your not calculating the GI for the people shadows they probably won't match up, intensity wise that is. You'll be able to fade them outin combustion but only globally, so there will probably be some mismatch.

Here's a thought though, what if you treat the people like RPC's and set them to not cast shadows. Set the building elements in VRAY Props as matte and set the alpha to -1 and render out sequence of tga's from the lights point of view with separated alphas (you'll either have to use a spot really far away for VRay or a parallel light with the scanline renderer (and set up a new matte material) as I've had trouble rendering out orhtographic views via VRAY). They'll have to be pretty hires though to encompass all of your scene. Next, calc your GI like you described (i.e. no people), save it and set to use that file. Load the alphas from the previous pass into the projector of the light and in the material editor set it to invert. Just tried it here and because the ground plane,etc already have the GI calc'd the 'shadows' also get muted. Only thing I don't know is how to load up a series of stills in the proector map without loading a avi or quicktime, anyone? **edit**Just hit the sequence button when you load up the frames, duh**edit**

Technically this doesn't answer your question (people only shadow..) but it does avoid calcing every frame with the people. Hope it helps.

[timmatron]

Hmm, I hadn't thought of using a project light. Sounds like a good idea.

[miraldo]

to load a series of images you can use the IFL format. in the "select bitmap" dialogue box, if you choose one of the frames and turn on "sequence" the IFL file is created automatically.

[flino2004]

http://www.spot3d.com/vray/help/VRay...rials_anim.htm

[timmatron]

http://www.spot3d.com/vray/help/VRayHelp150beta/tutorials_anim.htm

Yeah thats the one I was refering to. I had a hard time understanding it, and I really did try.