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View Full Version : Nasty black refractions even with huge trace depths

happychopper
03-15-2009, 05:24 PM
Hi guys, embarrassing problem here... some nasty black refractions on simple objects (check the pics) even when dialling up all the trace settings to large amounts.

I've got an A+D material, based on physical glass (with 30cm refraction falloff to yellow) and even with enormous global trace depths, max refs, max refract as well as equally large ref + refract settings in the material the pesky black patches turn up.

The pic shows the liquid object from a drinks bottle and a test chamfer cube. Both are nice clean poly objects and are sitting in a completely white self illuminating sphere (so there's no dark corners to reflect)

The settings in the first pic are : Max Trace Depth: 100, Max Ref: 100, Max Refract: 100 and on the A+D material: Refract 100, Ref 100

And the second: Max Trace: 3, ref: 3, refract: 3, A+D Material: 3, 3.

I'm completely miffed by this - cann anyone assist?
happychopper
03-15-2009, 05:51 PM
It's my "max distance" and "color at max distance" settings... they're buzzing the material all the way down to black (even though they're set to a nice lemony yellow).

Still don't understand exactly why, but at least the problem black patches have gone...
happychopper
03-15-2009, 06:56 PM
My other error was not using photometric lights - that has properly cured the problem
AdrianWilliams
03-16-2009, 01:47 AM
could you upload the scene so we can have a play?
happychopper
03-16-2009, 10:17 AM
Not really, it's a work job and I'm NDA'd. I'll whack the finished job up on my site. What I've learnt from my tinker on Sunday night is that for perfect CG bottles:

Photometric lights: a must (I'm lazy and was stuck in my ways to standard lights)

A+D material: work up the base glass preset but be careful using "refraction max distance" and "colour at max distance" - this is where you'll be landing yourself is dodge black spots area. A+D material is designed to work with photometric lights only.

Read the help file around the A+D material section about IOR settings and geometry - why can't Maya's manual be like this?!?! I'd tried doing this but wasn't sure how - the method explained is clear and concise. Thanks to Pete Draper for pointing it out.

Phil
TwiiK
03-17-2009, 09:54 AM
Is it completely fixed for you now that you're using photometric lights?

I had the exact same problem and was unable to fix it. I set every refract/reflect trace depth setting to the maximum and I still had black in my glass. My environment was even illuminated white and I was using photometric lights.

I tried with just using colored transparency and also the color at depth setting, but I still had black in my glass.

The object I had problems with was a bottle almost identical to yours and my black areas where in the exact same positions. The bottle was green glass with a brown liquid inside, modeled properly like described in the A&D help files. But there was black visible where you have black in your render.

I never bothered to make a thread or try to sort it out, but seeing as you did I'm curious if it's completely fixed. :)
happychopper
03-17-2009, 04:41 PM
Not sure there - throw the file over if you want and I'll have a look at it.

In the 'render settings' the trace depth I'm happy with at the moment (for a single bottle render) is 10 (total), 8 reflections, 5 refractions.

For the A+D material I've left them up at 30 for ref and refract but these numbers get clipped by the 'render settings' numbers mentioned above.

Bung us a test file and I'll have a look for ya,

Phil
happychopper
03-18-2009, 12:40 AM
Twiik, Are you sure you've got the IOR of your liquid material set to something around 0.8?
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