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Pavlov
05-19-2013, 05:39 PM
Hi all,
maybe not everyone knows this: if you use LW's sRGB workflow, and if you disable ANY tonemap option into Kray, you get identical results. The only idifference is in translucency, because Kray will take GI in account.

The thing which fooled me for a while is that Kray's preview is NOT sRGB compatible, so you see gamma compressed render (darker) while it computes, but when it's done, you'll get a gamma corrected result and it will look exactly like VPR.
I find LW's sRGB very nice in terms of hues and shades, so i wanted to match it with Kray, because it has a much superior GI (expecially for corners), and i found this.
So an optimal workflow is: set everything in Lw with VPR, and render just final image in Kray to avoid LW's nasty issues in small detail GI.

Paolo

Nicolas Jordan
05-19-2013, 07:17 PM
I have no trouble getting getting GI detail with Lightwave in the corners of geometry with my renderings. Settings like this tend to work well. The most important part is probably setting the "Minimum pixel spacing" to 0.1. You can also leave the "Minimum pixel spacing" at 1.0 and simply crank up the "Multiplier" setting to something like 200% instead of the default %100 and you should get a similar result.

Pavlov
05-20-2013, 01:59 AM
hi,
well... with 2 bounces probably it's ok, and it depends on the interior anyway.
I've a 5 bounce interior with lot of indirect light, and even with rays 1000/500 and MPS 0.3 it's quite splotchy, and it takes several hours for a 2500 pixel image. Kray solves it nicely with no splotch at all in 1 hour, and it's 100% identical. Anyway i'll try with lower MPS, but times will be killer.

Paolo

Pavlov
05-20-2013, 02:11 AM
Another question: Kray's pics seems to be correctly seen into image viewer, and i can save them from there.
I cant get them saved in sRGBG from image saver (they are saved dark). Any suggestion =?
And again, what does exactly sRGB means ? It doesnt seem to be the classic gamma /2.2 in and *2.2 out, like Linear Workflow should be. Anyone knows exactly which kind of correction sRGB performs ?

thanks,
paolo

Pavlov
05-20-2013, 02:58 AM
i.e. here are two pics. One is Lw's corrected one, the other is Kray's, which just got the sRGB compression, but is saved dark.
Is there an automatic action (no manual tweaks please) to bring Kray's one to sRGB colorspace in PS ?

thanks,
Paolo

Ztreem
05-20-2013, 03:12 AM
Can't you load the image in LW and show it as sRGB and save it out?

Mitja
05-20-2013, 03:16 AM
i.e. here are two pics. One is Lw's corrected one, the other is Kray's, which just got the sRGB compression, but is saved dark.
Is there an automatic action (no manual tweaks please) to bring Kray's one to sRGB colorspace in PS ?

thanks,
Paolo

I believe you can't do it in PS, since the color space affects textures/maps too (and befor the rendering). Or something like that.
Have you askef in Kray's forum?

Pavlov
05-20-2013, 03:35 AM
Ztreem, yes it work... you load the render and set it to Linear into image editor, and it's corrected. Thanks 1
Mitja - this pic is rendered using LW's sRGB, so Kray already got a correct sRGB input for textures and everything. It just missed the sRGB correction OUT.
The method above fixes it, and tyou get a Lw-matching output.

Paolo

MSherak
05-20-2013, 04:18 AM
i.e. here are two pics. One is Lw's corrected one, the other is Kray's, which just got the sRGB compression, but is saved dark.
Is there an automatic action (no manual tweaks please) to bring Kray's one to sRGB colorspace in PS ?

thanks,
Paolo

http://filmicgames.com/archives/299 (Great expanation of Gamma)

KRay works with Lightwave CS when the tonemap is disabled. This is cause KRay hands a linear image back to LW and it handles the CS. So for your test renders you are correct in disabling the tonemap.

When you want to render the frame (or sequence) and output it from KRay you have to set the it Tonemap to what would be sRGB since the save does not go though LW's CS. So the settings you want when you store the image from KRay are:

Tonemap:Gamma
Limit DR after Tonemap
Parameter 2.2
Exposure 1.0

This will save the image from KRay exactly like you see with Lightwave and sRGB set. Just have to remember to set it back to disable and don't limit to work with LW CS again or basically KRay will hand a sRGB image back to LW CS and it will get another sRGB applied. Glad to see you working with color space.

-M

Pavlov
05-20-2013, 04:56 AM
Hi,
yes i guessed that, but problem is Gamma 2.2 is not exactly like sRGB. There's something sRGB does on colors too (not just brightness), and it's not reproduceable within Kray tonemapper.
Loading it into LW image viewer does the job so it's solved... anyway i'd like to understand really what exactly does sRGB profile, beside linear workflow compression and decompression.

Paolo

MSherak
05-20-2013, 05:35 AM
sRGB and gamma 2.2 are close. Yes there is a difference. Check out the link.

http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/

Breaks down the math between the conversions. If you want all the control of your image just save out as .HDR in KRay and edit it in Photoshop. PS will use the ICC standard to display the image in sRGB. And if you want to lock the look of this in the in the HDR, duplicate the background then convert to 8-bit. This forces PS to use the ICC instead of pulling up their HDR to LDR panel.

-M