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Just shadows thanks... no illumination.

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sector09
Just shadows thanks... no illumination.
on Jul 26, 2007 at 7:55:25 pm

I'd simply like to ad lights to a scene, casting shadows on a specific surface, without illuminating that surface as well. How do I go about doing this?

At first I tried light-linking / shadow-linking... but I'm obviously doing it wrong.

Then I've tried the use-background-shader on an offset copy of my suface, but this seems like a very clumsy solution.

Please excuse my ignorance & help....



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SSGGMM
Re: Just shadows thanks... no illumination.
on Jul 27, 2007 at 12:09:03 am

Try creating a new render layer. Click the little flag. Go down to render pass options. Uncheck beauty, check shadow. Render. Look at the alpha.



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Steve Sayer
Re: Just shadows thanks... no illumination.
on Jul 28, 2007 at 2:33:10 pm

One cheap trick you can use is the following:

1) Create your light(s), have it illuminate both the shadow-casting and the shadow-receiving surface (could just leave 'illuminates by default' on).
2) Set the intensity of the light to be very low, like 0.001. This will not add any noticeable amount of illumination to the scene.
3) Set the shadow colour to be darker than black--do this by clicking on the shadow colour swatch, and typing a very large negative number in the 'value' attribute. Putting a value of -1000 will produce a normally-dark shadow from this minimial-intensity light.

The 0.001 and the -1000 get multiplied by one another to produce a value close to 0, which is normal for a shadow. By bringing the shadow value closer to zero, you make it appear paler. You can add colour, too, but the hue will be reversed due to the negative sign.

Sometimes this is useful, sometimes not... maybe it will work for you. Good luck!

-Steve


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Steve Sayer
Re: Just shadows thanks... no illumination.
on Jul 28, 2007 at 3:03:43 pm

Addendum: this works differently for raytraced vs. depth map shadows. A quick test showed that using values between 0 and -1 for the raytraced shadow worked better; the extremely large negative values work for depth map shadows.

I tried with Maya software, not sure about mental ray etc.

-Steve


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Marco Loreto
Re: Just shadows thanks... no illumination.
on Sep 19, 2016 at 2:17:28 pm

Hi... I know this is a very old thread, i'm using Maya 2016 and i can't use negative values for the shadow color, i type "-1" and it turns to zero when i press enter.

I tried to do the same in a computer's friend with Maya 2015 and it worked. Is this something that changed in Maya 2016?

Please, help me out! Thanks!


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