View Full Version : Raytrace shadow transperancy
07-05-2003, 08:40 AM
These pictures illustrate a problem I am having with Maya 5's ray traced shadows using transparency.
The first picture shows the fully opaque 'hair' (no transparency) working as I would expect.
The second picture shows what happens when I assign a transparency map to it - the shadow almost completely disappears.
The third picture shows the shadow object with 'primary visibility' turned off but 'cast shadow' is still turned on, you can see clearly that the shadow is barely showing up, although more appears at the top of the head - the area at the back of the head should be completely black.
The fourth picture shows the head model with no shadow object for reference.
So I'm wondering how to get the hair shadow object to cast a shadow as seen in the first image. Is this a bug in Maya or am I doing something wrong?
What if you duplicate your hair object - assign a fully opaque shader and turn primary visibility off. Now turn off cast shadows on your visible hair object and map as you like.
07-06-2003, 03:07 AM
Thanks for your reply colt, but that doesn't actually solve the problem as I want to use a map with holes in it to cast the shadow. The shadow I want has to have softer edges than straight geometry produces.
Thanks for your time. :)
07-06-2003, 03:22 AM
Looks like your light's 'Ray Depth Limit' is too low.
(If that's not it, check that you have enough shadows under raytrace quality in render globals -- it can be limited globally or per light, whichever's lower.)
07-06-2003, 05:58 AM
Thanks for the reply Jeremy. I tried raising both of those values and it didn't make any difference.
Might be time to start that 'Class-Action Against Alias|Wavefront's Rendering Engine' thread I've been thinking about...
07-06-2003, 06:56 AM
Sorry. Still seems fixable: Export just selected geometry to a new file, load that and in the new scene add a new light and new shaders. Make sure it's a raytraced shadow, the surface is double-sided, it's not refractive, you have enough refraction steps, use an ordinary shader like lambert or phongE, try the same scene in Mental Ray for comparison . . . it should just be a little clicking around probably faster than the lawsuit.
07-07-2003, 04:49 AM
Thanks for the reply Jeremy. I tried doing what you suggested and again it didn't work - Mental Ray giving the same result as the software renderer.
What I did find seems to work is making sure that the surface has two sides (as opposed to also being double-sided), so that two sections of geometry pass between the lights and shadowed surface, such as with a sphere.
I found that lofting the hair surface back on itself and repeating the texture seems to do the trick. I still get the transparent section showing up slightly but that has been a bug in the renderer for many versions (though they did actually fix it at one stage).
Thanks again for your help. :)
07-07-2003, 06:10 AM
Getting transparency maps to show up in shadows, that was never possible with Depthmaps right? Just wondering if that was another thing they fixed over the years and I missed it... :)
01-15-2006, 01:00 PM
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