Shadow Colour

[creaty]

How would you alter the colour of a shadow in Softimage 3.9? I have ambient light turned off.

[pomme]

The colour of the shadow is based on the effected object's ambient colour. Shadow's colour is not able to alter. Let's say if you have 2 objects are in the shadow, one blue and one red. In real world, they both doesn't have the same colour of shadow. Same as 3D. If you are able to alter the colour of the shadow. Let's say you changed it to dark green. Then both object will appear a wired looking shadow.

[fredc]

I would swear I saw a shader for this not long ago. However, if nothing else comes up try this.

1. Create a copy of your object (hope it isn't a large character, if so you might try an instance.).
2. On the copy, go to material editor, make the object's diffuse color what you want, like red. Then select it to be a shadow object, and partially transparent.
3. Make your shadow light source exclusive, and then assoicate your original object with it. This is so only your copy casts a shadow.

That's it. You should now see a colored shadow. In this case it should have a redish tint. You might even be able to pull off a "free" soft shadow by selecting blur (on the material dialog). It seemed to work in my test, but I hesitate to say it is a real solution for this, since it would seem to cause a paradox and rip a hole in time and space as we know it. )

Of course you can always do it in post with a shadow pass.

Hope this helps,
Urp

[creaty]

Thanks for the help but I found a way to make the shadow colour.

First make a spot light with the colour you want the shadow to be, in this case red (RGB 1 0 0 ). This light has no shadow settings applied. Then duplicate the light and make the light colour RGB -1 0 0. Turn on shadow for this light and in the scene you will get a red shadow but no red light.

[fredc]

Your right. I use this technique for shadow passes, but I never thought about using it for colored shadows.
Nice idea!!!

Urp

[devdoka]

The problem with this method is that the lights need to be exactly opposite in color with matched positions/orientation in order to maintain color balance within the scene. Also, your render times will increase with each light added. If you need to change the shadow colour, then both lights must be editted each time. You also can't easily adjust the shadow umbra factor.

If you're using mental ray, you can use an alternate solution:

1) Select original object and de-activate shadow rays. This makes the object visible to the camera and in reflections.
2) Duplicate the object. Turn primary and secondary rays off, turn shadow rays on. This makes the duplicate invisible to the camera and reflections, but still casts shadows.
3) Make duplicate partially transparent in the material editor.

Using this method you don't need to futz around with the lights which keeps render times lower and leaves the door open to create other inclusive/exclusive groups for your lights. You can also texture the duplicate object to create patterns in your shadows (such as blur maps to create raytraced soft shadows without using area lights). Mental ray is a faster renderer anyway.

Matt

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Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com