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Stankluv
11-15-2009, 01:31 PM
So, if I export a .ma file from zb 3.5 with a fresh color texture map from polypaint and a freshly baked displacement map; and then open that file in Maya.

Then if I want to work in a linear/adjusted workflow and change my render options>quality>framebuffer> gamma to .4545, set my Data type to "RGBA (Float) 4x32 Bit and render out to .exr; my question is what do I do to my default exported-from-zb textures.

My instinct is to apply a gamma +2.2 adjustment node to each of the maps, but I am looking for some confirmation and ideas about how some other people are popping their Zbrush 3.5 .ma exports into Maya for this work flow.

I have been in a production environment where I barely understood the reason at the time, but the lighting sup was advising me to tweak the dispmap file node's color balance values for reasons of this purpose. I prefer the gamma node for the sake of book keeping ease. I am just seeing if I am in the ball park to what other peole are doing



Thanks.

Nathan
11-16-2009, 08:25 PM
actually you want the opposite.
you want to put a 2.2 gamma on your framebuffer, and an inverse gamma (.4545) on each texture coming from zbrush.

also, you only want the gamma on the framebuffer for "previewing" the render. you don't want to save the image with that gamma baked in, so you want to use it just to see how the renders look as you're setting them up, then disable the effect when you render to .exr

I've also found that the framebuffer gamma method is kind of screwy (at least it used to be). your best bet is to use a lens shader on the camera. select your camera, open up it's attributes, scroll down to the mental ray settings, and add an "mia_exposure_simple" to the "Lens Shader" slot. when you do that, it should be set automatically to 2.2, but double check it to make sure.
then when you're ready to render to file just remove the lens shader or set the gamma to 1.0

Stankluv
11-16-2009, 11:11 PM
ok, thank you for your reply.

Just to be clear, what I have been doing is setting my frame buffer to .4545, and adding the lens shader at 2.2, for preview purposes, render with lens shader gamma at 1. Render out to .exr.


does it matter which number value is used, as long as they cancel themselves out to 1? Or was I just totally bass ackwards?


Thanks again.

Nathan
11-16-2009, 11:39 PM
leave the framebuffer gamma at 1.0 and never change it.
lens shader at 2.2 for preview, then set lens shader to 1.0 to render to exr.

the gamma 2.2 will make your render brighter and washed out initially. you need to compensate for that with lighting adjustments and use linear textures (.4545 gamma on zbrush textures).

and yes, you want to use 2.2 and .4545 as those most closely mimic the conversion from linear space to video/srgb space.
also, whenever you open one of your rendered out exrs, most likely whatever you are using to view it will be automatically applying a 2.2 gamma, so it should look the same as your preview framebuffer.

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11-16-2009, 11:39 PM
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