dare i say - linear work flow...

[chrisjacks21]

I have finally taken steps and begun to look into using LWF, I realise that this is old ground and well documented by many people. My main confusion arose around the differences between the Max and Vray frame buffers and saving out images when using this workflow. So I have outlined below my initial understanding of the BASIC process.

1. In Max preferences:
- enable Gamma/LUT Correction
- set Gamma to 2.2
- select ‘Affect colour selector’ and ‘affect Material editor’

2.When opening bitmaps, change gamma to 2.2 in the gamma override box (or use colour correct plugin)

3. Rendering with Max frame buffer (MFB):
- Your render will be gamma corrected in your MFB.
- However if you save as tga/tif/jpg etc, the gamma will not be burned into the image, you will have to adjust the gamma in photoshop using the inverse gamma setting (0.4545)
- Alternatively save as EXR file, this will carry through the gamma correction in linear space

4. Rendering with Vray Frame buffer (VFB):
- Your render will appear dark, click on the ‘display colours in sRGB space’ in the VFB. This will preview the gamma correction - if you save as tga/tif/jpg etc, the gamma will not be burned into the image, you will have to adjust the gamma in photoshop using the inverse gamma setting (0.4545)
- Alternatively save as EXR file, this will carry through the gamma correction in linear space, no adjustment needed in photoshop.
- Alternatively if you want to burn the gamma into the image, go to Vray Colour mapping, leave type to Linear multiply and set gamma to 2.2. Now in VFB, you don’t need to use the sRGB preview button, your render should appear correct and when you save as tga/tif/jpg the gamma is burned in and no photoshop adjustment is necessary. (Note, don’t save as EXR if using colour mapping gamma as end image will have double gamma applied.)

If I am INCORRECT in my understading, feel free to correct me!!

I hope to try and roll out this workflow on future commercial projects.

[3LP]

Hi chris,
i think you're close to the thing.

There is a tutorial on aversis website that explain quite well the LWF 2.2
http://www.aversis.be/tutorials/vray...l_gamma_01.htm

and alternatively you can use this plug-in :
http://www.chaosgroup.com/forums/vbu...ad.php?t=42988

I use it it's really great !


Hope it will help

Best regards

Stan
3LP Team

[instinct]

you're pretty much there. Keep in mind tho that rendering linear (NO burnt in gamma) you should go float by all means. As the .4545 reverse gamma will make you loose quite a lot of color information when going the 8bit route.

Regards,
Thorsten

[chrisjacks21]

3LP - yes I have seen both those tutorials, both very useful.

Instinct - i will bear that in mind, working in float is another workflow that I want too try and incorporate in future projects

[Crayox13]

Also trying to switch to LWF. You guys always use exr?? I always saved in tga until now, and adjusted exposure in VFB.

[Clifton Santiago]

@chrisjacks21: All sounds right, except in step 2, why don't you just set the bitmap input gamma in preferences to 2.2, so it does it automatically to any bitmaps?

[Crayox13]

Also, darker areas will now appear less detailed, when using this gamma, what would you guys use to improve this? Change some thresholds or just increase subdivs?

[Clifton Santiago]

@Crayox13: in Color Mapping, set your gamma to 2.2, and click Don't affect colors (adaptation only). This allows V-ray to take samples at the 2.2 gamma so that there are enough samples in dark areas, without affecting the gamma of the rendering.

[Crayox13]

Awesome! Thanks for this important tip. One other thing I find now strange. Gray colors have been scaled a lot, so now I have many light gray colors, but only few dark gray and then suddenly black. Is that ok? It seams wrong.

[Crayox13]

Also, my screen is calibrated with Spyder3Elite. In options it says gama 2.2 Is that ok? Or should I set my screen to gama 1.0, if yes, how?

[Clifton Santiago]

In theory, you could do gamma at 1.0 and then adjust all your software to work with that, but I think that sounds difficult. I set my monitors to sRGB profile, calibrate with Spyder 2 Pro (I need to upgrade) to gamma 2.2 and 6500 K. All software except Max seems to work correctly with those settings by default.

As for your grays, or contrast, you need to keep practicing until you understand how to light your scene in a gamma adjusted environment. Previously you have been overlighting your scenes because you were fighting against the gamma curve of you monitor, which is too dark in mid-ranges. Now that its corrected, you just need to get used to it. It should only take a few days. Withing about a week of switching to LWF my renderings were plenty dark and contrasty. I would recommend either re-doing the lighting, or switching back to 1.0 for old scenes. After a few months, even your old scenes will be LWF, so you won't have to switch back any more.

[Crayox13]

Ok, so my screen should be left with this profile.

But, what I meant in MAX, the problem now is (still haven't light my scenes) color picker bar. You know, the vertical one that has intensity - nuances of gray from white to black. It used to be linear, but now almost all vertical bar is light grays and on top I have only few dark grays and then suddenly black. Does that make any sense? Does everyone else has this in LWF?

[Clifton Santiago]

Oh I see. Yes, that's a side effect. I just get used to it and select colours based on what I see rather than specific rgb values. If you need specific rgb values, or want to see your colour swatches in linear, just use the colour correct plugin.