Chaos Corona Forum

General Category => Porting and API => [Archive] Chaos Corona for Maya => Topic started by: hugojackson18 on 2015-05-12, 05:46:57

Title: Rendertime Difference when Colormapping_Gamma On
Post by: hugojackson18 on 2015-05-12, 05:46:57
Hey

I've noticed a massive difference in render time between when I start the render with Colormapping_Gamma on 2.2 or on 1.
I'm not using Corona's own colormapping as I'm using Maya_2015 new color management system and I'm using a Custom LUT, but when I put the Colormapping_Gamma at 1, it is much much longer than when it is on 2.2, and I can see that it's sending a LOT more samples when it's on 2.2

Any reason for this? I've read somewhere that brighter images were longer to render, so I was wondering why it was the opposite here.

Here's a couple of images

You can see as well that if I put the gamma back to 1 AFTER the render is complete, the image is identical.

Render started with Gamma at 1 (ColorManagement ON)
(http://s30.postimg.org/kurmk6d75/test_gamma_1.jpg)

Render started with Gamma at 2.2 then reverted to 1 after the render completed (ColorManagement ON)
(http://s14.postimg.org/77s1ise2p/test_gamma_2_2.jpg)

Gamma at 2.2 with ColorManagement ON
(http://s27.postimg.org/s297o71ar/test_gamma_2_2_Color_Man_On.jpg)

Gamma at 2.2 with ColorManagement OFF
(http://s15.postimg.org/siscvifm3/test_gamma_2_2_Color_Man_OFF.jpg)

I find it a bit obscure, so I thought there might be an issue somewhere. I don't mind using Corona's Colormapping but I'd much rather using my custom LUT.

If anyone knows why this is happening, as it's a really stranger behaviour to me.
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: hugojackson18 on 2015-05-12, 05:49:55
EVEN WEIRDER

When I start the render with Gamma at 2.2 AND Maya's Color Management is OFF from the start, it's even quicker to render!!!

(http://s28.postimg.org/bun2nqbn1/test_gamma_2_2_Color_Man_OFF_Start.jpg)

I was looking for render times optimisation, that might be the fastest i found!
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: hugojackson18 on 2015-05-12, 06:01:14
It would be great as well if someone could write a detailed explanation of what this part of the render settings exactly do.

(I'm talking about the bottom part of it, with all the samples options.)
(http://s11.postimg.org/6psw1k5k3/Untitled_1.jpg)

I know the manual is outdated (this part is not even in the manual) but if someone could tell me, I could actually try to update the manual with some of the infos I found here and there.

Thanks!
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: romullus on 2015-05-12, 09:12:29
You can go there and look into performance rollout: https://corona-renderer.com/doc/
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: maru on 2015-05-12, 11:23:36
It would be great as well if someone could write a detailed explanation of what this part of the render settings exactly do.

(I'm talking about the bottom part of it, with all the samples options.)
(http://s11.postimg.org/6psw1k5k3/Untitled_1.jpg)

I know the manual is outdated (this part is not even in the manual) but if someone could tell me, I could actually try to update the manual with some of the infos I found here and there.

Thanks!
I guess Corona settings work the same for different software versions so you can read about most parameters in our helpdesk (it is currentlt 3ds Max-only):
https://coronarenderer.freshdesk.com/support/solutions/folders/5000156713
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: hugojackson18 on 2015-05-12, 23:05:44
Cool thanks guys for the docs!
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: haggi on 2015-05-12, 23:31:10
I'll have a closer look at the gamma differences. Seems really strange to me.
Title: Re: Rendertime Difference when Colormapping_Gamma On
Post by: Ludvik Koutny on 2015-05-12, 23:39:18
Hmm, this could be due to the Maya's native VFB perhaps spending more CPU time on redrawing and gamma correcting than Corona does on rendering itself?