Include shadows in `Material ID`

[joethelion]

Hi there !
Is there a way to include the shadow of an object (made of a material X), in the `material ID` channel in of material X ?

[andybot_cg]

That's a good question. Is there a way to make a "shadow catcher" material in vfsu?

here's the first thread I found explaning it: http://www.chaosgroup.com/forums/vbu...033#post251033

I know there's been plenty others since.

[fpedrogo]

Unfortunately we don't have the matte shadow option in V-Ray for Sketchup, but we do have the matte shadow channel and the shadow channel that allows you to save all the shadows in a different render.

Best

[joethelion]

Thanks for the replies. I was trying to render an object in a box; create a mask with the object and its shadows, so that I could add or remove the object as a layer separately, as there are many such objects. It seems I`ll be able to get its shadows only if I render objects one by one using the matte shadow channel.

[andybot_cg]

I would use a different material for each separate object, and then give each of them a different material ID color. Then if you select the "Material ID" VFB channel, you'll get a saved image that has a different color mask for each object. This way, you should only need to render once, and you can select which object to mask or include by color.

[joethelion]

Actually I`m doing that already but my problem was; when the object is in place it should also have shadows, whereas when I use material ID only, I can`t have the shadow information. And as there are many different objects, shadows get inside each other when rendered in one go, and shadow matte channel becomes useless, That`s why, I was thinking if I sacrifice the shadows of an object on another object; but settle with the shadows of the object on the box itself only, then rendering one by one should work I think.

[andybot_cg]

oh, right - overlapping shadows would be an issue... hmm, complicated. Guess you are stuck with multiple renders.

[joethelion]

I guess so, but thanks anyway