View Full Version : Maya Shaders not rendering transparency maps? :(

12 December 2011, 02:37 AM
so another night of pure bugs and one more to add to my frustration list :(

Can mentalray not render transparency maps?? any maya shader blin, phong etc I adjust the transparency colour and the object renders transparent. Now I ad a simple black and white map to the channel and the object remains at full opacity!? tried it with diferent maps still no effect.

I cant even find a mentalray material with transparency!! whats going on??

12 December 2011, 03:24 AM
Depends how the map looks and the UV's on the objects.. How are you plugging it into the transparency?

And the mia_material_x is the main MentalRay material, it's used for most things, it has transparancy, as well as many other great features, including physically accurate shading.

But the map should work with any materials transparency.

12 December 2011, 04:19 AM
One of two things might help:

1. Are you linking your mia_mat_x into your shading group in the mental ray section? You'll want it connected to Material, Shadow, and possibly the Photon slots if you're using GI.

2. In the mia_mat_x is a slot for "Cutout Opacity". This is different than transparency, but both can be driven with a texture map (image file or otherwise). The Cutout Opacity is how you knock out leaves, for example, or for hair shading sometimes too.

Hope that helps. Not really a bug, just gotta know where to look sometimes! There's a lot to learn with this stuff.

12 December 2011, 07:49 AM
Also make sure that the "alpha is luminance" checkbox is checked when you are connecting the alpha (the blue line in the hypershade).
It is in the "Color balance" rollout (in the file node for example).
Otherwise you'll connect anything if the file has not his own alpha... this tricked me more than once :curious:

12 December 2011, 11:03 AM
Thanks for the suggestions guys,

After fiddling with settings I managed to get some results with the mia_material_x, Alpha is luminance wasn't set so checking that sorted it out, cheers nookie :) Though still no joy with maya shaders :(

12 December 2011, 11:27 AM
InfernalDarkness: you were right about the cutout channel, that seems to be the one to use ;)

12 December 2011, 11:44 AM
ok mia_material_x is just doing wierd crap now. I moved the light and the colour turned black with shadow in some wierd refractive way. I cant turn off refraction. I just want a simple material to use as a mask and I still cant get the standard maya material transparency to work :(

12 December 2011, 11:27 PM
I've run into a problem where material_x will render transparency to the alpha SOMETIMES. I've played around with it for hours to see if I could find a reliable fix, but it was still hit and miss on a per render basis.
I'm rendering my background elements separately and comping them, so here's my workaround:
Copy the transparent object(s) to a new layer and assign it a white surface shader. For objects that intersect the transparent object and should mask the transparency, add them to the layer and assign them a surface shader that is black. You can also set the alpha of this surface shader to black so it will erase from the alpha, but all you need to do is render this layer (which will go very fast) and use it as a luminance mask to comp the bg into your transparent objects. This has the huge added advantage of post render options (blur, distortion, transparency, etc.) to control your refractions.

12 December 2011, 01:28 AM
I've never had problems rendering an alpha cutout pass with Cutout Opacity, in the mia_mat_x_passes. Perhaps we should set up a test scene and dissect it, see if we can't reproduce the issues?

I have had some issues with z-depth passes and the regular, non-passes mia_mat_x shader. This should seem evident however, as the _passes shader is designed for passes, and the standard _x is not.

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12 December 2011, 01:28 AM
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