Full linear setup in Sketchup

mattvanwyk · 18 Apr 2016, 09:49

Last week i've been searching the internet for a good answer on this but nothing helped.
Tutorials have been written for 3ds max but nothing for SU.

I read up on Linear workflow and decided that i really wanted to give it a shot as it handles refl refr etc much more realistic.
As far as i know SU2016 in combo with Vray 2 is a linear setup, so all my inputs (jpg, png etc) should be gamma corrected before i insert them in the project for it to do the math correctly (correct me if i'm wrong here plz)

In Vray we all know the color mapping options tab, but my question is: how should those settings be if i want to work truly linear inside sketchup/vray. Should i also make adjustments inside the SU preferences itself?

So far i've been using uncorrected jpg's as textures and used the Reinhard colormapping with 0.85 burn ratio but this is not true linear as far as i know...

Who can tell me how to setup SU and Vray to work fully linear?

Thanks you in advance!

valerostudio · 19 Apr 2016, 19:02

Its a good question and I think you have not received a response because most SketchUp/VRay users are not using that workflow. I have yet to understand how LWF works in a SU environment because we are missing a critical component that MAX has, which is the LUT/GAMMA options in the preferences. It's those settings in Max that 'correct' the textures as you bring them into the Mat editor.

I have always just used linear color mapping with clamping off and save to 32 bit EXR files and have not had any issues, but I might have been doing it wrong the whole time.

http://www.3dtotal.com/tutorial/1552-linear-workflow-the-whole-shebang-3ds-max-v-ray-misc-after-effects-by-daniel-dye-render?page=3#.UG3nP000V8E

I don't think the purpose of LWF is that it gives more realistic renderings. I think you can still make a crappy rendering with LWF, there are a lot more things at play there then just your color mapping.

mattvanwyk · 21 Apr 2016, 13:44

And did you had the options "Correct LDR textures" and "Correct RGB colors" checked on? Or did you imported alread gamma corrected images in sketchup. or none of the above?

valerostudio · 22 Apr 2016, 15:14

Why would you ever manipulate a texture outside of the engine? Is that what you are suggesting? You should never have to correct them outside of your engine, my understanding is that you have to tell the engine to correct them because VRay is using 1.0 Gamma.

I just read this tutorial and it is all starting to make more sense to me.

http://www.aversis.be/tutorials/vray/vray-20-gamma-linear-workflow_01-old.htm

Based on what is being said here, my guess would be that you should NOT tick those on as long as you have Input Gamma set to 2.2. Although maybe you need to tick them on for Correct RGB? I guess it might be worth a couple of test renders with it on and with it off. If you test it, post your results.

I just have never understood it. All I know is that if I export to EXR and use Linear mapping with clamping turned off, I can get what I need from Photoshop as far as correcting lighting goes.