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joie
11-26-2009, 05:59 PM
I am studing renderman for maya with the demo and would like to know how renderman deals with linear space rendering.

Should I do something to render in linear space like I do in mental ray?.

Thank's.

Xharthok
11-26-2009, 07:49 PM
Well, you can go to the Rendersettings -> Passes -> Pass:Final Defaults -> Outputs and increase the value in the second field under Exposure to 2.2 (Gamma). But you have to convert your Textures to linear space (e.g. with a gammaCorrect node set to 0.45). Remember not to gamma correct your Bump/Displ maps. Also all your color swatches are now wrong and you have to correct it for proper display.

joie
11-27-2009, 07:21 AM
So I have to do exactly the same things I usually do with mental ray, I thought renderman dealed with those issues the correct way, you know, it's Pixar, they always do things the correct way :P

kiryha
11-27-2009, 08:40 AM
I never have deal with linear workflow in renderman. Just render passes that u need with 32bit depth and get the desire result at composin stage. No need to think about gamma, swatches or any alike mentalray headache. But i use renderman, not renderman for maya.

joie
11-27-2009, 08:51 AM
If you don't change gamma in the textures or renderer and you render in 32 bit depth and do that in postproduction..., isn't that the same as render in Mental ray also in 32 bit depth?, I'm confused.

kiryha
11-27-2009, 10:02 AM
Im confused about this question for long time too:) But i think its the same.
In mentalRay i use exposure node on my cameras, because its easy way to get nice picture. I dont change framebuffer gamma, leave it at 1. Sometimes i do gammacorrection of my textures, sometimes i dont(the main my goal- get nice picture with less aforts, if its posible to do it without extra nodes-its ok for me). Render in 32bit float and than compose all the stuff.

leif3d
11-27-2009, 06:25 PM
You have to do what Xharthok explained.
Gamma correct any color swatch manually, as well as textures.
In RfM or Slim you can add a Renderman attribute to file textures for gamma correction. It's called "apply sRGB" under the texture RM attribute. This will allow for correct display in the viewport and de-gamma at render time, unlike the gamma correct node.
If you have RMS you can set the gamma to 2.2 in IT (similar to MR lens shader). If you have RfM you can set the gamma to 2.2 under Final Defaults > Outputs > Exposure (gain, gamma), but it will be embedded in the image, instead of being a LUT.

if you are skipping any of this, you are not doing a correct linear Workflow. That doesn't mean you can't do incredible art working the wrong way though, that's a whole other subject...

leif3d
11-27-2009, 07:08 PM
Now, that sRGB attribute for file textures is great, but How about procedural textures or ramps?, that attribute isn't avalable...


That would be a good request to post in the pixar forums. :)

joie
11-27-2009, 07:10 PM
Thank's leif3d for the explanation, now this is great. I can change renderman's frame buffer gamma to 2.2 and check textures sRGB and then everything renders the way it should.

Now, that sRGB attribute for file textures is great, but How about procedural textures or ramps?, that attribute isn't avalable...

Thank's in advance.

joie
11-27-2009, 07:15 PM
Mmm, I guess I can try to ask for it in the demo section of the official forum... :)

ndeboar
11-28-2009, 01:50 PM
yeah, slim really should come with a gamma node. I ended up just writing one from scratch.

I've also written a new delux shader that converts all color inputs it linear (.445), which is really what everything should do in the future.

leif3d
11-28-2009, 07:25 PM
yeah, slim really should come with a gamma node. I ended up just writing one from scratch.

I've also written a new delux shader that converts all color inputs it linear (.445), which is really what everything should do in the future.

It's probably possible to use an expression node to write a power function too...
But yeah, I agree, Slim could use a gamma node. I'm surprised there isn't one.

Are you planning to share your delux Shader or gamma node BTW?

ndeboar
12-01-2009, 01:53 PM
Are you planning to share your delux Shader or gamma node BTW?

Wrote it for work, so well ties into all our custom libs/aovs/ ect.

If people really want it, i can write a gamma node. It's really not that hard, check out Cutter on fundza, its what i use for all my Slim devleopment. It come with basic Slim templates, and you can quite easily bang up a gamma node from that. You can also publish straight to slim from it, which i love.

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