Contact shadows pass in Maya?

[user_deleted]

Does anyone have a trick for rendering out a contact shadow pass in Maya 3? I have a character and I want to just get a shadow around the feet - cast only by the area around the feet.

I've tried using a spotlight with decay regions - to isolate the light to the area around the feet and the shadow plane - but the shadows seem to ignore the decay regions.

Thanks,

Laurence Cymet
Lighter/Compositor
Calibre Digital Pictures

[scottr]

You could use a closetPoint on surface Node, but they are extremly heavy. It would create a color change on the surface when two pieces of geomtry get close to one another. Might work for a render pass.
Just a thought.
If you want me to email you one let me know.

-scott rays-
digital artist
Kleiser-Walczak Hollywood

In reply to:
Does anyone have a trick for rendering out a contact shadow pass in Maya 3? I have a character and I want to just get a shadow around the feet - cast only by the area around the feet.

I've tried using a spotlight with decay regions - to isolate the light to the area around the feet and the shadow plane - but the shadows seem to ignore the decay regions.

Thanks,

Laurence Cymet
Lighter/Compositor
Calibre Digital Pictures

[perseus2]

In reply to:
Does anyone have a trick for rendering out a contact shadow pass in Maya 3? I have a character and I want to just get a shadow around the feet - cast only by the area around the feet.

I've tried using a spotlight with decay regions - to isolate the light to the area around the feet and the shadow plane - but the shadows seem to ignore the decay regions.

Thanks,

Laurence Cymet
Lighter/Compositor
Calibre Digital Pictures

Can't you just turn shadow casting off for all objects but the feet?

[user_deleted]

Unfortunately, several of the characters walk with their hands or roll on the ground etc... Requiring many parts of the character to cast contact shadows - which made things even more complicated when those objects did not come in contact with the ground as they still cast shadows. We found that solution became more complicating than faking the contact shadows in combustion.

Thanks for the reply though.

[user_deleted]

In reply to:
You could use a closetPoint on surface Node, but they are extremly heavy. It would create a color change on the surface when two pieces of geomtry get close to one another. Might work for a render pass.
Just a thought.
If you want me to email you one let me know.

Unfortunatly we are doing a serial and "heavy" is a word that elicits an unfavourable response form my superiors. However, if you have a file handy I'd love to see it. You can e-mail me at laurencec@calibredigital.com

We've tried playing with intensity curves but they dont seem to affect shadow casting. The Ideal thing, would be a "slice plane" that can be found in Houdini and 3d Studio Max - which could be put above the ground and only allows surfaces that pass below it to be visble/shadow casting.

Thanks for your help.

[starrider]

Easiest way would be a negative light...parent it to the feet and give it a intensity curve for decay...that way you can control exact distance of the shadow or negative light....and make sure it only illuminates the ground as to not suck light off the feet too....

I imagine you could also texture map the color as to the shape of your feet making a perfect soft shape in the negative light....

mrPooH
www.TheLightOmelette.com

[sunil_born2win]

Hello Icymet,

you can use negative lights indeed, and restrict them to a small area, use the light linking options to have them affect only the low part of your model (provided it is in several parts), and also if you're using depth map shadows, use the options of Use Dmap in any axes. If your disable your light in all the axes, and only keep Use Y- Dmap, it will render MUCH faster. You'll find those option boxes in the attribute of the light, at the end of Depth Map Shadow Attributes column. Hope this helps

Alban

[user_deleted]

Assuming you have a FLAT floor/surface...

you might be able to coax a useable pass with the sampler node pointY output fed thru a range into the transparency of the shadow casting objects - with a directional light abovethis will give you a shadow for all surfaces that are visible (eg between y=0 and y=2).

This could be rendered from the camera view and comped in 2d, or rendered ortho from above, then applied to the floor as a shadow texture on the main render.

might work...

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"It's so obvious, it's bound to be a trap" - Cato