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control intensity of color transported with gi


jonas_bloch
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hi there,

we are sitting here in berlin getting started with vray.

we already finished a interiorviz for the new airport in berlin. we had to do the columns and ceiling all in white and the floor an red tone. our problem: due to gi we got a strong red touch on our white surfaces.

though we had to do some postwork in ps.

our concern: how can one control the amount/ saturation of color transported with gi?

 

we`d appreciate any hint.

one idea is to render an imap with a desaturated texture, then render the final image with the previous imap. didn´t try it yet.

 

thank you for your help,

 

regards,

 

jonas bloch

 

www.archimation.com

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Hi Jonas,

If surfaces with a particular material are causing too much color bleed, you can reduce the GI produced by those surfaces in VRay properties.

 

But unfortunately that also reduces the amount of light it is bouncing back too, and therefore will darken your scene. That's why I think the saturation control is better, because it just controls the color of the GI, not the color of all your materials, lights, etc.

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you can also use the material "VRayMtlWrapper" which you could use on the red material by choosing it in the material editor then clicking the "standard" tab and choosing "VRayMtlWrapper" without discarding the original red material which will be used as a base material. You are able now to control and reduce the generated GI for this material.

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...are you working in correct Linear Color Space? if not, this would help also. if you are working in Linear Color Space, but not viewing it with the a curve correction, then you are probably bouncing to much light around in your scene causing extra bleed.

 

This is the first and most important thing to check. If you are not working in the correct color space, your darks (shadows, bounce light) will be too saturated, working in the correct color space will solve a lot of this.

 

My approach is to try an many "natural" things as possible. Doing this by reducing the amount of color that a material has, changing the color of a light source, etc... changing the "saturation amount" of the GI will work, but is a last resort in my mind...

 

Also keep in mind that color bleeding is a real thing that photographers deal with every day. See attached image which is a real photograph that someone posted a while back on the vray forum.

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Yeah, now that just wouldn't look right without all that color bleed would it? So obviously a certain amount of color bounce is desireable and has a positive effect on the realism and unity of a scene.

I don't necessarily agree that switching over to linear workspace is the most important thing for this guy to think about. He is not saying he wants to completely change how he works and read through countless numbers of confusing threads on the Vray forum, only to adopt a method that will either be greatly simplified or even surpassed in the future. He just wants to turn the color bounce down a little bit. And that is a whole lot easier than doing the linear work space thing. I think it is definitely a method worth learning and using, but for this purpose, the best answer to his question is in my first post.

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I totally agree with Tim!

 

its simpler to control saturation than use LWF....and LWF is confusing. I probably have read every thread and tried to understand....but failed.

 

The Vray overide material works too..but i dont think its available in the released version.

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Yeah, now that just wouldn't look right without all that color bleed would it? So obviously a certain amount of color bounce is desireable and has a positive effect on the realism and unity of a scene.

I don't necessarily agree that switching over to linear workspace is the most important thing for this guy to think about. He is not saying he wants to completely change how he works and read through countless numbers of confusing threads on the Vray forum, only to adopt a method that will either be greatly simplified or even surpassed in the future. He just wants to turn the color bounce down a little bit. And that is a whole lot easier than doing the linear work space thing. I think it is definitely a method worth learning and using, but for this purpose, the best answer to his question is in my first post.

 

And how did you edit that photo? In Photoshop? Then take your render and edit it in Photoshop, that is what Photoshop is for. My point is learn to do things correctly first... it will benefit you in the end.

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good morning first of all,

and thank you very much for your comments.

impressive photo by the way, reminded me alot of our last viz.

meanwhile i had time to watch christopher nichols interior lighting tut yesterday. for sure we want to work in correct color space. this is new to us, but worth it to deal with. what an improvement to be able to work with hdr images. so thanks for the `hit one button get immediate effect` advice. this will also help. now it takes some time to implement things.

greetings,

 

jonas

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And how did you edit that photo? In Photoshop? Then take your render and edit it in Photoshop, that is what Photoshop is for. My point is learn to do things correctly first... it will benefit you in the end.

That is the ideal solution. But sometimes you just gotta do it the quick & dirty way too! :)

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Linear Space took a little time for me to grasp, but in reality, it is almost as simple as rendering without it. You only need to make sure Max's gamma controls are set properly, and that you have curve correction turned on.

 

The biggest pain for me is the lack of extensive support in Adobe products.

 

Anyway, I don't think Linear Space is going away, and it can only help me learn more.

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http://throb.net/site_main/LinearWorkflow.html

tutorial from sfrender

interior lighting tutorial by christopher nichols, chapter 7

 

....right now i`ve just a very rough idea about the linear space thing.

but the sources above will help me through it. that`s what i found.

does anybody know additional resources?

 

jonas

 

the hardest part for me was not grasping the concept, but understanding what settings i should be using in Max and Vray.

 

if i am set up right, i have the following...

 

Max

Gamma... 2.2

Bitmap Files.. Input 2.2, Output 1.0

 

Vray

enable curve correction of..... 0, .64 and 1.0,1.0 set to free.

 

make sure the curve it is not enabled when you save.

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where can i find the curve correction in vray?

is it in the frame buffer?

 

use the first button on the bottomof the frame buffer window to set it, and the 6th button over on thebottom of the frame buffer window to apply it.

 

if you are in middle of a project though, you may want to wait until next project. i have been able to make the switch mid project without to much of a problem before, but it is not recommended as it may screw up your materials.

 

another thing, i have 'effect material editor' checked in the max preference settings.

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