alpha channnel

# 1 26-08-2008 , 07:33 PM

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Location: Hastings UK

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I am trying to render a scene and need it to clip out my characters in the alpha channel when they walk behind objects in the scene. I have been told this is what I need to do but cannot work it out.

"You will need to Turn the church model into a black
hole matte object so it correctly clips the characters out in the alpha channel and I will also need a
separate shadow pass for your people as well."

Any help with this is much appreciated.

Thanks,

Leon

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# 2 26-08-2008 , 09:10 PM

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well if it's not a complicated object or if the object doesn't move a whole lot you can just create an animated mask layer in your compositing program to ensure the church shows and the characters 'go behind it'...

otherwise the 'black hole matte' is actually a material. it's called the 'use background shader' and when applied looks green in the viewport. it doesn't show up in renders but shows up in alpha channels, and it still receives shadows from the other objects in the scene.

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# 3 26-08-2008 , 09:49 PM

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Originally posted by NeoStrider
otherwise the 'black hole matte' is actually a material. it's called the 'use background shader' and when applied looks green in the viewport. it doesn't show up in renders but shows up in alpha channels, and it still receives shadows from the other objects in the scene.

Originally Posted by

The black hole matte is actually in the material attributes, blinn, lambert, phong etc etc, its in the matte opacity tab in the drop down menu.

You also get the option to overide cirtian materials in the render layers so that it does this for the layer its rendering.

You could use the surface shader, but the matte opacity is just the job for this.

"No pressure, no diamonds" Thomas Carlyle

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# 4 26-08-2008 , 10:06 PM

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Thanks for the advice guys, will give this a go this evening.

Thanks again,

Leon

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# 5 27-08-2008 , 10:15 PM

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Ok I have got things working but for some reason the skin is white. I cannot work out why this is and am trying to suss the reason. Any help is much appreciated.

Thanks,

Leon

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