maya_mental ray transparency and matte opacity probs

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Old 12 December 2007   #1
maya_mental ray transparency and matte opacity probs

As much time as I've spent in Maya, this continues to be a problem I can't figure out:

I'm rendering something with a shader that has transparent areas. The areas render as transparent, but their matte overrides the matte of what's behind them. Below are some images that more clearly explain the problem:

http://www.jewsus.com/question_tran...1_playblast.jpg
(basic scene inside of Maya)

http://www.jewsus.com/question_tran...n_02_render.jpg
(rgb of render, looks as expected)

http://www.jewsus.com/question_tran...ender_alpha.jpg
(alpha of that same render -- see how you can't see the nose of the plane? like the propellar's matte is overriding anything that's behind it, instead of adding to it)

http://www.jewsus.com/question_tran..._background.jpg
(the resulting image composited on top of blue sky -- you can see how this is a problem, since there's sky showing through where the nose of the plane should be)


Now I feel like I've really exhausted the options I know:

- in the shader I've tried mapping matte opacity to a texture, and everything else I could think of

- in the object attrs I toggled all of the mental ray properties involving transparency, etc.

- I made sure that raytracing is on and my rays counts are all turned up to 12


Has anybody solved this? I really would be enormously thankful if I could solve this.

Cheers,
Ben
 
Old 01 January 2008   #2
What shaders are you using? I tried a couple lamberts and I cannot replicate it. The object behind the semi-transparent object still has a complete alpha.
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Old 01 January 2008   #3
Quote: - in the shader I've tried mapping matte opacity to a texture, and everything else I could think of


you can use maya shaders just fine


Quote: - in the object attrs I toggled all of the mental ray properties involving transparency, etc.


Toggle off? Because you should toggle visible in transparency of the plane ON for MR to show the plane in propeller's matte.



I've had this problem before but when I understand how to tweak those attributes everything make sense.
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Old 01 January 2008   #4
details

The propellar is phong and the plane behind it is blinn. I have tried toggling all of the MR attributes both on and off and nothing seems to work.

I just tried making both objects have lambert shaders and there was no change. Perhaps I'm building the shader wrong... I have the texture's outcolor mapped to the shader's transparency. Matte is set to 'opacity gain.' I wonder why it's not working the same for you guys.

Well thanks for your help, if anyone else has any ideas I'd love to hear them!

-Ben
 
Old 01 January 2008   #5
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