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Powell
04-05-2004, 09:06 PM
After doing quite a bit of rendering in various software packages using Mental Ray, I believe that I have found a issue with Maya and Mental Ray. It always seemed that my Maya renders were way too bright when using HDRI and Final Gather. I have found that the problem is in the irradience color on all Maya surfaces. The Maya default irradience color is set to a value of 1.0 1.0 1.0.
When the Final Gather computes irradience on a surface, it should divide that value by .318 or pi...not the Maya default of 1.0. By going in and manually changing all the irradience values on on surfaces to 0.318 0.318 0.318 should solve this problem.

Let me know if this helps.

Jozvex
04-05-2004, 11:25 PM
Yes you're right, (but you already know that).

The other thing people have to remember is to disable Maya's default lighting. Unless you create at least 1 light in your scene, or specifically turn the default lighting off in the Render Globals, Maya will use three (I think) point lights as well as your FG or HDRI.

I like to create a 'null light' which is just a point light with 0 intensity. It turns off the default lighting, and then if I decide I want GI or caustics, I have a light ready for 'photon emission only'.

:thumbsup:

Randolph
04-06-2004, 09:35 PM
Originally posted by Jozvex
Maya will use three (I think) point lights as well as your FG or HDRI.

I think it's only one directional light by default. God knows how many test renders I messed up by forgetting to turn if off... :rolleyes:

Anyway, it seems a matter of what version of mr you use and sometimes of the hdri image itself. Some people/tutorials tell you to connect the hdri to the ambient and the colour node, some to the ambient only, some tell you to adjust the colour gain values of the HDRI node, some say that you should use a lambert material, some to apply it to a surface shader etc.
Maybe we all should go back to three point lighting and die in peace ;)

Jozvex
04-06-2004, 11:12 PM
Haha. I'm a surface shader and 'adjust the colour gain' guy myself.

Hopefully Maya 6 might have a proper HDRI adjusting tool like the free plugin for Max.

Powell
04-07-2004, 12:46 AM
Ive found that adjusting the gain of the image tends not to be the best way. Usually when you are raising or lowering the gain on an HDR image in Maya, it begins to clamp it. This clamping can add quite a bit of extra unwanted noise to the final render. (*especially if you are using a HDRI that was compiled from lightprobe images!*) If you want to adjust the values of the image itself, Id reccomend using HDRI Shop and changing the image exposure. Too bad maya doesnt have a feature like that built in....

Jozvex
04-07-2004, 04:26 AM
Yeah, that's what the Max plugin can do (it was made by Blur studios for Brazil but it's free to be used without it). It has histograms etc.

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