Shadow creation without light

[Benken]

Why dont you render out a Shadowpass and then ad the object (with a nother light setting) in Photoshop....If you understod my bad english :)

[ThirdEye]

In C4D we have a "shadow caster" checkbox that does exactly what you need to do. Maybe there's an equivalent in Maya? :shrug:

[CaptainObvious]

If Maya allows for lights with negative intensity, you can do it the following way:

Create a light with negative intensity and disable shadow casting for it.

Duplicate the light, and flip the intensity to a positive value, and enable shadow castic.



The negative light will make the scene darker everywhere. The positive light will bring it back up to the previous brightness everywhere except where the shadow falls, so now you'll have a dark shadow and the rest of the scene will look like before.

Turn off specular highlights for both lights, too! And lens flares etc should obviously not be used either.

[tedious]

In Maya, you don't need to use the "two lights" trick (although that way works too...)

To make a Maya light cast shadows only, just set its color to black (so it doesn't brighten anything) and set the shadow color to a -1 value (so it darkens where the shadow is cast.)

Tedious

[JacobCarmona]

Tedious that single technique works only with raycast shadows not with raytracing shadows. :sad:

[neuromancer1978]

Its been a few weeks since I booted up Maya - but isn't there two Emit checkboxes - one for Diffuse and another for Specular? Turn them both off and the only result is a shadow?? I could be wrong, but I think that would work?

[CaptainObvious]

Its been a few weeks since I booted up Maya - but isn't there two Emit checkboxes - one for Diffuse and another for Specular? Turn them both off and the only result is a shadow?? I could be wrong, but I think that would work?
That won't work, because a shadow is just a lack of light. If a light doesn't make anything brighter, it won't make the shadows darker. You'll have to trick the renderer, basically. Lights that just cast shadows without illuminating anything are not physically accurate worth a damn.

[jeremybirn]

To make a Maya light cast shadows only, just set its color to black (so it doesn't brighten anything) and set the shadow color to a -1 value (so it darkens where the shadow is cast.)

Yep, that's the simplest way to do it in Maya. It works with dmap and raytraced shadows, too.

-jeremy

[gerardo]

Yes, the trick that use one black light with negative shadows works in most 3D apps. Depending on your scene you may want to try also to fake shadows with some occlusion shader (ctrl.occlusion maybe?). In most 3D apps this is commonly quicker than raytraced soft shadows.



Gerardo

[ChrisSosa]

I think if you apply a use background shader on all your ellemnts that will be receiving the shodows in your scene + the positive and negative light source you should be able to render out just the shodows in your scene. I work at a studio that uses the same technique. Though I think I might be missing a few steps.

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