View Full Version : Object completely ignored by Final Gather?

07 July 2011, 04:56 PM
Hey guys,

I have a problem here with 2012, is it possible to make an object fully ignored by the final gather? I just want it for reflection purposes. I unchecked Final Gather Cast and Final Gather Receive but it still affect my render (stopping the FG rays outside of my reflection sphere surrounding my scene, for instance).


PS: Also the additional color of the mia_material_x_passes doesn't work as intended (not making it incandescent). The small preview shows me how the shader should be, but it renders as if no texture was connected to it, can someone confirm? I compared with 2011 and it definitely doesn't work in my maya 2012.

07 July 2011, 06:12 PM
There's a custom attribute "FinalGatherHide" you can use to block an object's Shape Node from any FG calcs, entirely. DJX wrote a wicked little script ( to make it even easier.

07 July 2011, 06:45 PM
Damn, I think I saw this script last week, but I completely forgot about it... Thanks :thumbsup:

07 July 2011, 01:50 PM
Coming back with my incandescence / additional color / surface shader problem. There seems to be a huge problem with converting the intensity units when using a mia_exposure_photographic. While the scene is lit correctly, these incandescent or surface shaders will be black unless you boost the Cm 2 factor, and then burn all the other shaders.

It works fine with a mia_exposure_simple...

07 July 2011, 01:59 PM
Leave the cm factor how it was and increase the value of the colors of the individual surface shaders etc. You'll probably need very large numbers. I've had values like 1000000 depending on my scene.

You may be interested in taking a look at the mia_lightSurface shader (I think thats the right name). You can use this as an alternative to the surface shader and it gives you independent control over reflection and final gather contribution.


07 July 2011, 05:09 PM
I actually tried to multiply the color value of my surface shader by 100 000 but I couldn't see any difference, maybe I should have continued.
Anyway, since camera lens shaders are not rendered in passes, I got rid of it, I have to do the tonemapping in post.

Thanks guys

07 July 2011, 09:51 PM
I actually tried to multiply the color value of my surface shader by 100 000 but I couldn't see any difference, maybe I should have continued.

This isn't really the best way to get the results you're looking for, and obviously having to crank the values up that high with no results isn't helpful for you. I've done the same thing before though, I feel your pain!

For light-emitting shading, you really should be using the mia_light_surface shader, which plugs into the mia_mat_x in the "Additional Color" slot. This shader has three main controls (Intensity, FG Contribution, and Reflection Contribution) and a few other controls, such as per-light specific linking and the main Color of course, which can be linked to image files for example.

Some rough examples from another thread here:

The lightbulbs themselves, here...

And here, at the tips of the chandelier lights (from an actual, physical lighting fixture I had to model for this scene...) :

I use this shader for anything that lights up, short of say Portal Lights and stuff like that. Anytime your light source is geometry (bulbs, tube lights, LEDs) this shader is very helpful and renders quick too.

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07 July 2011, 09:51 PM
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