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

[rfellers]

What is the best way to determine the gamma and correct on an LCD monitor?

[cpnichols]

I have foudn that the free version of this:

http://www.praxisoft.com/pages/products.wiziwyg.html

Is a pretty good way to calibrate your monitor, if you don't have a probe or anything. WAY better then the adobe gamma thing that realy screws things up.

[Sawyer]

See I thought I had it but...

I was viewing GI Interiors which I just got last night and Chris in your section on linear space your drak bright mulitpliers are set to .4545, .4545 not 1, .4545.

Now I have not finished the dvd yet but that was confusing to me.

[timmatron]

See I thought I had it but...

I was viewing GI Interiors which I just got last night and Chris in your section on linear space your drak bright mulitpliers are set to .4545, .4545 not 1, .4545.

Now I have not finished the dvd yet but that was confusing to me.

I just covered that part too and that was also my understanding. If you are set to linear color mapping, you keep it at 1, but if you use gamma correction color mapping, then you set to .4545....but I have yet to try it out.

[DaForce]

Chris what is so bad about the adobe gamma thingy?

[Gijs]

Chris what is so bad about the adobe gamma thingy?

if I may answer,

it is highly inaccurate, it has to do with the patterns, they don't work well on most monitors. I haven't tried the program Chris pointed to, but the Aim dtp method is a lot better than using adobe gamma only. (actualy the aim dtp uses adobe gamma, but not for evaluation)

[Sawyer]

Sorry about the confusion. You should use dark=1 and bright=1/gamma. I've edited the wrong post.

This was what I went from originally but on the interior gi dvd Chris has both bright and dark set to .4545 or 1/gamma.

[Gijs]

I have just made some tests: when using gamma correction,
bright multiplier=gamma correction
dark multiplier=global light multiplier (example: if this value is 1, and you render with a vray light with multiplier 8, it is effectively the same as rendering the scene with a light mult. of 16 and a dark mult. of 0.5)

Now I think of it, this is pretty handy if you want to turn the light intensity down globally (or changing from old non-linear scene to linear)


Vlado, can't this easily be changed to something like this:
global light mult: ...
gamma correction: ...

when color mapping is set to gamma correct?

[cpnichols]

Sorry about the confusion. You should use dark=1 and bright=1/gamma. I've edited the wrong post.

This was what I went from originally but on the interior gi dvd Chris has both bright and dark set to .4545 or 1/gamma.

Yeah... there is a mistake in my DVD, and I figured it out after it was recorded, which was a while ago, after a conversation with Vlado. The reason I set both to 0.4545 was a matter of habit, and poor labeling of the Color-Mapping.

A long with an apology for the confusing (especially on a subject that is confusing to start with), I should explaing why I accidently misled you.

When color mapping first came about it only had the "Exponential" option. At which point you could add a multipier of 2.2 to both Light and Dark, to come close to a gamma corrected image. It was not exact, which is why the "Gamma Corrected" option was added. By habit (and since the labels had not changed) I habitually changed both to 0.4545.

The correct thing to do is as has been posted above: bright = 0.4545, dark = 1.0

Again, sorry about the confusion.

[throb]

The correct thing to do is as has been posted above: bright = 0.4545, dark = 1.0

Again, sorry about the confusion.

honestly, i would avoid that at all.
i would use the viewer button that goes to sRGB which is in later builds.
until then use a LUT ala my tutorial.
why?
this way your mats, etc get the gamma applied and what you see is what you get.

[cpnichols]

The correct thing to do is as has been posted above: bright = 0.4545, dark = 1.0

Again, sorry about the confusion.

honestly, i would avoid that at all.
i would use the viewer button that goes to sRGB which is in later builds.
until then use a LUT ala my tutorial.
why?
this way your mats, etc get the gamma applied and what you see is what you get.

I want to make sure and let you know that I agree with Throb on this. I believe that I make that point on my DVD. Someone back me on this. But there are those that don't have the ability to write out float and have float editors that can do the gamma for you, so I explain that method (a hack) to burn that gamma into the image.

[Gijs]

until then use a LUT ala my tutorial.
why?
this way your mats, etc get the gamma applied and what you see is what you get.

which is exactly what gamma correct color mapping does, only more accurate I suppose (a real gamma curve). If you are using the linear float data in the first place, why would you avoid gamma correction color mapping? The advantage using gamma correction over the LUT-curve is that Vray adjusts its sampling to it (importance sampling). The effect is that you don't need to increase your subdiv. too much to get the shadows noise-free.

As a side note I want to emphasize again that sRGB is a standard not developed for monitors, but for TV. There is no monitor that has a sRGB response curve naturally. So it may be good for film industry, but for other purposes, sRGB is most of the time not a color space to aim for.

[timmatron]

Chris, in your dvd you didn't mention anything about adjusting Max's gamma to 2.2, but all the other tutorials I have seen are saying to do that. I guess I'm a little confused about that.

[cpnichols]

Chris, in your dvd you didn't mention anything about adjusting Max's gamma to 2.2, but all the other tutorials I have seen are saying to do that. I guess I'm a little confused about that.

Actually I do... I mention it in Chapter 6 when talking about texture baking. Applying the gamma in Max, allows you to see the material that are in gamma corrected space, as well as render the image in Max in correct space.

[cpnichols]

The advantage using gamma correction over the LUT-curve is that Vray adjusts its sampling to it (importance sampling). The effect is that you don't need to increase your subdiv. too much to get the shadows noise-free.

Not really convinced that this is true. If you look at the rawRGB, and rawGI, it would seem that Vray still does everything in linear space, (as it should) and then applies the color mapping at the end. Either way, I think that adjusting "Clr thresh." in the Irrdiance mapping would be a better way to push more samples in the darks.

I also think that pipelines and methodology is something that will be debated for a long time.