Continuing on my previous post Mental Ray Production Library– Enabling mip Shaders .We can now start exploring the available new nodes.

In this session we will have a closer look at  how to use the mip Shaders, in particular the mip_rayswitch_environment, the mip_cameramap, and the mip_mirrorball
to composite 3d elements onto a live action background.

The HD vr. can be found here.

The following is Zap comment on the video

“Nice work Ash.

I only have one, single, tiny comment on all this; To adjust the brightness of the shadow, the “correct” way to do it with this shader is to modify the “ambient” parameter.

Changing the shadow density of the light is bad, it is always evil. “Shadow density” of a light makes no physical sense. In real life, what causes shadows to not be pitch black is other light coming into it from other places. “Shadow density” style settings has always been a horrible insane nonphysical hack, and are a type of setting that you should never touch if you want your rendering to have any form of “physical” meaning.

To clarify; whatever you put into the “Ambient” parameter of mip_matteshadow is properly counted as this “additional light”, and will behave correctly, get occluded by the AO ets. Setting the “shadow color” of the light will just make part of the light go straight through the object, and this will not let your AO lock it down properly, because the AO is only applied to the ambient component, so this “part of light” you are letting through the object will always illuminate the matte plane, never allowing it to go “black” anywhere, which can be problematic.

Of course, when you do very small changes (such as you did) it might not be a bit progblem. Just thought I’d let you know, though

And anyway …. other than this minor nitpick, you are 100% spot on with the rest of the tutorial.

Nice work!”

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This entry was posted on Sunday, October 25th, 2009 at 5:46 pm and is filed under Maya, Mental ray. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.