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layers and alpha

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jo_graphix
layers and alpha
on May 28, 2007 at 10:07:14 am

i have an animation of 2 elements, the first element is sometime over the second one and sometimes under the second one...


i need to render 2 layers but with specific alpha channels to composite them later in combustion or after,

somebody could give me a small help in maya how to export layers with correct alpha for each layer?
actually each layer export normally with normal alpha but without considering other layer.

or it should be compoisited using Z depth later in combustion?

i am lost...
much thanks if somebody can help me and tell me the professional solution for this problem.



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Chad Briggs
Re: layers and alpha
on May 28, 2007 at 12:52:26 pm

There are many, many ways to handle this, but the most straightforward is that you'll have to render out both elements as a seperate pass, using a useBG shader on everything else in the scene.

For example, say you have a blue ball and a red ball, circling around each other. You can set up one pass where the red ball has a usebg shader, a second pass where the blue ball has a use bgshder on it. This will effectively cut out a hole in the alpha where the other ball is supposed to be. You can also achieve the same thing by using the black hole setting on the shaders for the ball. (i think)

Lastly, you can render one pass with both balls in the scene, then render another pass with a pure red and blue shader, ambient color at 100%. Then you would take this layer into your comp app and tell it to use the solid colors as an alpha channel. This can be a nice fast way to generate several alphas at once.

hope that helps
Chad


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jo_graphix
Re: layers and alpha
on May 29, 2007 at 6:29:45 am

thanks. sure it helps, i will try it.
the project is visible here:

http://test.graphixmotion.com/transition_v5b_cam3_h264.mov

(17mb)


thanks much.



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