Indirect illumination question

decumano · 2 Feb 2014, 10:37

Hi SUers,
I have a little problem with this scene: the scene is quite like I want, but if I try to set the background texture more yellow the external color of the white wall becames yellow.
This is normal, and if I decrease the "indirect illumination-post processing-saturation" value I solve the problem; but this setting modifies all the scene; what can I do to modify only this texture reflection?
The material has default settings.
I'm using Vray for SU version 1.48.93

Thanks guys

andybot · 2 Feb 2014, 14:44

I would use your "material ID" pass to create a mask for your exterior walls. That way you can fine-tune the color in post-processing. Another thought is to try adding a material to the exterior that is slightly blue to counteract the yellow.

decumano · 2 Feb 2014, 15:10

Thank you andybot.. the second choice seems to be difficoult, is not easy to find the correct match between colors

the first: I never used the ID pass... I found this page: http://www.chaosgroup.com/en/2/material_ID_channel.html
so, with this method I should use a post-processing software... and probably I would lose all shadows... isn't it? And the image could appear quite flat

I don't know. Doesn't exist a way to directly overlay the material color?

jiminy-billy-bob · 2 Feb 2014, 15:57

The Material ID pass is just a way to quickly select the material in photoshop, using the magic wand.

decumano · 2 Feb 2014, 16:17

Right, ok... and then I could change the color manually... It's ok, but if I wanted to do an animation I would not use PS for all the frames... this is the reason because I would find a direct solution

rspierenburg · 3 Feb 2014, 13:01

Well I suppose you could set up a Batch macro in PS to do all the frames after you figure out the first one.

andybot · 3 Feb 2014, 15:32

yep, animation gets complicated quickly. If you had something like Adobe AfterEffects, you could use the MaterialID as a mask in the video, but doing a batch process in PS would still be tedious. That's basically why I was thinking if you can counter-effect the color shift directly in the render by playing with colors, it may be a lot simpler once you get something you like directly from vray.

andybot · 3 Feb 2014, 15:37

@decumano said:

Thank you andybot.. the second choice seems to be difficoult, is not easy to find the correct match between colors

the first: I never used the ID pass... I found this page: http://www.chaosgroup.com/en/2/material_ID_channel.html
so, with this method I should use a post-processing software... and probably I would lose all shadows... isn't it? And the image could appear quite flat

I don't know. Doesn't exist a way to directly overlay the material color?

glad you found my tutorial

It's not exactly the same process for what you need though. Like jiminy-billy-bob says, you just use the materialID as a mask by selecting the area, and using a new hue/saturation adjustment layer to adjust the colors of your original render. You don't have to delete out any of your original rendering (or its shadows) to make the adjustment work.

valerostudio · 3 Feb 2014, 16:46

@andybot said:

yep, animation gets complicated quickly. If you had something like Adobe AfterEffects, you could use the MaterialID as a mask in the video, but doing a batch process in PS would still be tedious. That's basically why I was thinking if you can counter-effect the color shift directly in the render by playing with colors, it may be a lot simpler once you get something you like directly from vray.

I think if you made an action that uses Select Color Range and you pick that ID color and run that batch, it should work effectively.

andybot · 3 Feb 2014, 18:36

@valerostudio said:

@andybot said:

yep, animation gets complicated quickly. If you had something like Adobe AfterEffects, you could use the MaterialID as a mask in the video, but doing a batch process in PS would still be tedious. That's basically why I was thinking if you can counter-effect the color shift directly in the render by playing with colors, it may be a lot simpler once you get something you like directly from vray.

I think if you made an action that uses Select Color Range and you pick that ID color and run that batch, it should work effectively.

Is there a way to batch the process so that PS will load the correct main pass and the mask for each frame, without loading each one individually?

Also - for the mask, I would just use white for the materialID color, as you are only doing that one color. This would simplify making the layer mask...

dkendig · 3 Feb 2014, 21:50

ouch! Or you can use the wrapper material on the ground plane, referencing the texture that you are currently using on the ground plane, and set Generate GI to 0.0

dkendig · 3 Feb 2014, 22:17

here's an example scene

wrapperExample.skp

decumano · 4 Feb 2014, 08:06

Oh, I'm sure yesterday I replied... I was wrong.
So thank you all for your posts! Andybot so that's your tutorial? Well...
With animations I usually use the batch to correct the frames... but as andybot said, loading pass for every frame is a problem...
and dkendig solution (referencing texture..) is complex for me, sure!

Probably the only one... is to find the correct match between colors, I'll try.
Even if, it's really strange that is not possible to set the material texture as totally not-reflecting, would be useful.

Thank you all

rspierenburg · 4 Feb 2014, 12:21

Unfortunately Devin I don't think the Wrapper solution would work in this case as the OP is using Version 1.48.93

andybot · 4 Feb 2014, 13:21

@dkendig said:

ouch! Or you can use the wrapper material on the ground plane, referencing the texture that you are currently using on the ground plane, and set Generate GI to 0.0

Of course! Though like Rob says, it depends on having 2.0

Actually, can you get the same effect by adding another diffuse layer that's gray and not having the original layer contribute to GI? Can you only get that effect with wrapper material?

dkendig · 4 Feb 2014, 15:58

whoops! I missed that version number... 1.48.93? Any reason you're not using at least 1.49.01? It was a free upgrade. You might end up saving enough time using the wrapper material in to justify the upgrade cost to 2.0. Depends on the learning curve required to do this all in post, and time it takes to actually get the result you want.

Andy- I don't think there's really any other way around it, excluding what has already been discussed, aside from doing two separate render passes. One with just the model, and the other with the ground plane. That's how I would have done it back in the day.