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LWF - what am I doing wrong?

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15 years 4 months ago - 15 years 4 months ago #1338 by nickroz
Problem:
I just realized that the Linear Workflow color mapping checkbox in Vray1.50sp3 is supposed to be unchecked for LWF. Now gamma seems baked in to EXRs in After Effects.

Workflow:
Max2010>SolidRocks (0.8x)>VFB(1.50sp3a)>OpenEXR format @1.0gamma>After Effects CS4. I'm using ProPhotoRGB colorspace for all maps, so it's 1.8 gamma workflow.

Settings:
Max: Gamma/LUT - 1.8 input, 1.0 output, affect colors/selectors=ON
SolidRocks: Gamma Correction on, 1.8, LATER button selected (don't affect colors, adaptation only)
Vray color mapping: Reinhard, g1.8, 0.3 burn, no clamp, linear workflow checkbox deselected (they really need to rename that)

Process:
I set cameras and light according to the SR minipreview (with gamma 1.8 on, LATER deselected).
I'll send out some half/full process renders to VFB (with g1.8, LATER selected) and use sRGB in the VFB to view the exposure.
Final render is from SR (g1.8, LATER on) to VFB. In VFB, I turn off clamping, turn off sRGB and save each channel as EXR to 1.0 gamma.
When I open in After Effects, the image looks as it did with sRGB on in the VFB.

Notes:
1. Monitors all calibrated with a Spyder3Elite.
2. After Effects is adjusted for Linear 32-bit workflow in the ProPhotoRGB working space.
3. In After Effects, the EXR footage is interpreted as sRGB2.1_____ on import. It says the colors are linearized to display correctly in my monitor colorspace. If I try changing to ProPhotoRGB interpretation, all the colors get oversaturated.
4. In my previous workflow (with the linear workflow color mapping checkbox selected), I would do the same process and have to apply an inverse gamma (0.5556 for 1.8) to the EXRs in After Effects.
Last edit: 15 years 4 months ago by nickroz. Reason: forgot the a in sp3a

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15 years 4 months ago #1339 by subburb
Hi NickRoz,

you're right, this checkbox need to be renamed...
spot3d.com doc says :
"Linear workflow - when this option is checked V-Ray will automatically apply the inverse of the Gamma correction that you have set in the Gamma field to all VRayMtl materials in your scene. Note that this option is intended to be used only for quickly converting old scenes which are not set up with proper linear workflow in mind. This option is not a replacement for proper linear workflow."

if i understand well, the resulting image in AFX is just like if gamma 1.8 is already applied ?
and, you're right, if the "later" button is ON when rendering with Sr, normally the render is computed "as is" it have gamma 1.8, but don't apply it, letting you apply gamma later in AFX.

So, houston, we've a problem.

i'm actually making 0.8x build, for max2010/SP3a compatibility.
i must say that gamma things in max2010 are just a pain to implement/understand.
Fortunately Autodesk team is very reactive.

please can you tell me if you've had the same problem with max 2009/sp2 ?

i need to find if the problem is max2010 related, sp3 related, or both to make the right correction.
and your feedback can help ;)

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15 years 4 months ago #1340 by nickroz
I hadn't got my head around LWF in 2009/sp2, so I can't help you there. Seeing as though I was using the LWF checkbox in sp3a - I haven't really got it now either.

I ran some tests. This is from a scene I setup with SR0.75/0.8x and I had the LWF checkbox on (probably not the best test scene). When rendering:
-LWF checkbox is now off
-all saved through VFB with clamp off and sRGB off
-all saved as JPG/1.0gamma and EXR/1.0gamma then brought into AFX for review

1. JPG looks fine as-is in AFX. EXR needs 0.55 gamma (1.8 inverse).

1.exr

2. JPG highlights blown out in AFX. EXR looks close as-is.

2.exr

3. JPG looks fine as-is in AFX. EXR needs 0.55 gamma (1.8 inverse). SAME AS #1??

3.exr

4. JPG needs 1.8gamma curve to look like EXR in AFX. EXR shadows good, highlights blown out.

4.exr


If you could provide an ideal test scene, I'll run tests again.
n

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15 years 4 months ago #1341 by nickroz
Ok, if I understand correctly - since I had the LWF checkbox on while setting this scene up, my camera/sun is overcompensating because all of my materials had an inverse gamma applied (darker). In that case, all of these renderings should be darker/less contrast because my sun should be turned down and my materials should be at normal gamma.

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15 years 4 months ago #1342 by subburb
butbutbut... where did you get your 0.8x build ??

yes Sr is intended to manage LWF without any correction in materials. this can explain.

as i'm not deeper than you in the lwf process, prehaps can you tell me what's wrong with SR, and how it should work to your eyes ?

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15 years 4 months ago #1346 by nickroz
You sent me the 0.8x build a couple of weeks ago to get rid of the annoying gamma popup.

I wouldn't change much with SR- maybe just overrides to manage gamma on a more advanced level. It would be nice to know exactly how the gamma was programmed into your script so I could work in LWF.

Ideal workflow would be to bring in g1.8/2.2 maps and have Max gamma/LUT prefs ON. Rig cams/lights using minipreview in SR and/or VFB with sRGB ON. Send out final renders (later ON) through VFB to 1.0 gamma and comp in AFX/Nuke/Combustion.

Maybe you could make a LWF gamma sticky so we can all figure out the proper SR LWF.

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