How to get better VRay renders (aka working in linear space)

[jujubee]

Here's the results of the settings with 771+ diffuse materials (I kinda got lazy with the naming throughout the apartment) changed from 2.2 to 2.5 colorcorrect, 2.5 Max gamma bitmap and input, and 1/.4 gamma correct:



You can see in reference to my second image that the colors are now lighter and shadows are slightly brighter. I dont know if the results warrant taking a scene from 2.2 to 2.5.

[flipside]

CCS, your exterior with materials applied looks sturated enough on my monitor! I would even say a bit oo saturated (especially blue and red), sky and grass seems ok. The light shadows are simply because you use a 1/1 balance on your sky/sun. Maybe this looked different before, but on a sunny rendering I always use at least a sun twice as bright as the sky color, or even more. for example sun 1.2 and sky 0.5, take care not to blow out light areas.

Juju, how do you use adobe gamma for two different monitors? I don't seem to succeed in doing that. I also have dual screen (crt and lcd on one system).

Cecil, normally you calibrate your monitor to a 2.2 gamma. So you have to do this for your laptop too. If you don't calibrate, you have to test with the gamma charts from aimdtp to figure out what your monitor gamma is.

Here is my test. It is a little dark (at least on my monitor) but this is because when I made this image, I didn't calibrate my monitor yet. So back then it looked brighter. This is straight out of max:



I'll do another test with stronger sky etc to get it light enough straight out of max. I changed nothing to my mats compared to earlier tests in the appartment thread, only the color correct gamma correction (no extra saturation etc...). Without this linear workflow, I always had to heavily post process in PS to get rid of blown out areas, I also used GI saturation back then etc... Now Everything looks right straight out max, without any tricks.


Ok here's the lighter test, straight out of max:

[cecil gittens]

Flipside, here an image of the latest project i am working on. I did not do any post processing. this is stright out of max. Gamma color correction
LM 0.434
DM 1

Cecil G

[jujubee]

Wow Flip - your scene turned out pretty well and it doesnt looked washed out. So you've applied CC to all your diffuse channels set to 2.2?

[flipside]

Look pretty good to me. I usually like the strong sun effect. I think in your image the sun should be a bit stronger, if you look at the image from a distance, you almost don't see that there is a sun shining trough the windows.

[flipside]

Wow Flip - your scene turned out pretty well and it doesnt looked washed out. So you've applied CC to all your diffuse channels set to 2.2?

Yep, and then the things as discussed before and as cecil uses. Display gamma=2.2, gamma color mapping, vray vfb--->save.

Oh and I used fur on the rug instead of displacement

[Gijs]

@jujubee, what is the value of your brightest white in your scene?

[jujubee]

@jujubee, what is the value of your brightest white in your scene?

Bright - you are correct about reflectance values but to the best of my knowledge this isn't washing out the scene.

@Flipside - I just took a look at your file (thanks for sending) and we're doing the same steps. The big difference I am seeing is that you have adjusted your lighting to the VFB so it 'previews' in VFB correctly - and this looks excellent. But if you copy this to Max frame buffer or save out to .exr and import into PS, your rendering will be washed out. Also, if you apply throbs curve in the VFB, this will show you what the 'burned-in' floating point values look like - again a washed out image. VFB by default does not show the linear workflow space.

[jujubee]

Hmmm. Thinking about this and I think it's making sense now. Perhaps VFB is displaying it (gamma correction color mapping to 1/.45454) correctly, but with Max preferences set to 2.2 gamma and viewing it in the MaxFB, or saving out to exr (again using Max's exr export function), perhaps the gamma is being applied twice from the Max gamma settings stemming from burned-in Vray processing.

Could the VFB preview in relations to applying the Gamma correction Color mapping been right all along? This would make the other methods of viewing the information false. This method was introduced after the tutorials were written and I don't know if our writings reflect this methodology anywhere.

Edit - Flip. Sorry, I think you were right and I was wrong. I think some of us are introducing an extra correction by saving out to exr (stemming from Max gamma 2.2 settings.)

This in turn brings up another question - if we want to save out with this method to exr/hdr, how do we negate the double correction? Do we have to do this by switching off Max gamma 2.2 every time or do we have to bring down the gamma values for the HDRs in postprocessing (which I've been doing all along- not shown in any of my previous images.)

[Gijs]

@jujubee, what is the value of your brightest white in your scene?

Bright - you are correct about reflectance values but to the best of my knowledge this isn't washing out the scene.

Also keep in mind that in this particular scene you are working on, your lighting and viewing direction is almost the same, which causes a lot of flatness in this image.

[CCS]

CCS, your exterior with materials applied looks sturated enough on my monitor! I would even say a bit oo saturated (especially blue and red), sky and grass seems ok. The light shadows are simply because you use a 1/1 balance on your sky/sun. Maybe this looked different before, but on a sunny rendering I always use at least a sun twice as bright as the sky color, or even more. for example sun 1.2 and sky 0.5, take care not to blow out light areas.

The oversat of blue and red is due to overaggressive self-illumination - easily fixed in materials.

Last night I came to a better balance of light/shadow with a 2.5 sun and a 1.0 sky - almost the same ratio as you mention! (Is there a benefit to halving them both as you did?)

My main question at this point is whether my image is done correctly. If so, then I can desaturate and otherwise adjust materials as necessary. But if my workflow is not proper, I don't want to waste my time. The key issue here is whether I can trust the image in the VFB for making these adjustments. (Again, I am using gamma color mapping.) Is my VFB image correct???

[Gijs]

The key issue here is whether I can trust the image in the VFB for making these adjustments. (Again, I am using gamma color mapping.) Is my VFB image correct???

if:
1 your monitor is calibrated well and
2 you are using gamma correct color mapping with bright=1/(calibrated monitor gamma)

then your VFB shows the linear data correctly.

[flipside]

Hi ccs, my ratio was just an example I made up 2.5 vs 1 seems good, it depends on the effect you want: how sunny it is and how clear the sky is.


Gijs, is it correct to say that when doing your points, the gamma is burried in the image, so in fact it is not linear anymore? When I save the vray vfb, it looks the same in an image viewer too, but jujubee seems to have problems when he saves his image as hdr/exr, looking like there is an extra gamma 2.2 applied. (he doesn't have the general bitmap export gamma set to 2.2).

[flipside]

---just a side note----

It's funny, the good old GoncaloP used this technique already in 2003, telling everybody and noboby listened. He didn't seem to know the technical reason like explained here, but still he managed to see the problem.
http://www.chaosgroup.com/forum/phpB...ighlight=gamma
http://www.chaosgroup.com/forum/phpB...ighlight=gamma
http://www.chaosgroup.com/forum/phpB...ighlight=gamma

It's a pity he suddenly vanished!

---end side note---

[jujubee]

He was pretty good, kind, and very helpful - shame to lose him.