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Indirect light in closed room
Posted: 07 December 2012 10:35 AM   [ Ignore ]
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Hello,

I got a simple white room with a spot light and indirect lighting (see pic).
When I give the floor in this room a simple color, the whole room get colored with indirect light (see pic). Is there a way to keep the indirect light, but not have it so colored?

Thanks,
Elele.

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Posted: 07 December 2012 11:11 AM   [ Ignore ]   [ # 1 ]
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I’ve always thought that color bleed seems excessive in Carrara but it never occurred to me to do such a simple experiment. That does look pretty bad.

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Posted: 07 December 2012 11:19 AM   [ Ignore ]   [ # 2 ]
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Things to try:
reduce the saturation of the colored surface (real life has no such equivilent as 100% saturated color)
Add an subtle ambient color that counter balances it (opposite color on the wheel)
Use shadow buffer lights with shadows turned down to 60% so they act as fake bounce light (watch out for transparent textures)
Turn down the GI to 40%

Carrara is an art tool, not a physics emulator. Does you scene have a white ceiling to bounce white light back into the scene?

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Posted: 07 December 2012 11:27 AM   [ Ignore ]   [ # 3 ]
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Seems to me that the purpose of Indirect Light is to provide a (cheap) approximation of real world behavior. It also seems clear that it could be doing a better job.

There’s no need to get defensive. This feature could be better ≠ Carrara sucks.

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Posted: 07 December 2012 11:52 AM   [ Ignore ]   [ # 4 ]
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Thanks for the replies smile

There is a white ceiling and the room is completely closed.
Making the color less saturated actually makes things worse, seems carrara adds saturation with each bounce.
Here’s an example with the floor 255 240 255 (light purple). There room gets a lot more purple than the original floor color.
To what should i apply the ambient color? To the light?
I don’t really want to add other lights to fake IL, caus I might as well just fake the IL then.

Also added a screeny with the render settings.

Also added a screeny of the scene, to show it really is only the floor that is colored :D

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Posted: 07 December 2012 12:36 PM   [ Ignore ]   [ # 5 ]
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That is totally bizarre. I’ve had some great results with GI. I see your render settings, which look fine. How do you have your lights and ambient lighting set up? With Indirect Lighting (Full GI) I think you want the ambient lighting set to 0, where you actually want it up higher than default when using ambient occlusion. Not sure if that will help.

Also what color are your “white” walls and how shiny are your surfaces - this also has an impact.

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Posted: 07 December 2012 01:03 PM   [ Ignore ]   [ # 6 ]
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The shaders are just plain colors with everything else turned off and a spot light (see pics).

BTW, I don’t want to complain about Carrara or “attack” anything. Sorry if it comes over like that. I’d just like to know if there’s a way to fix this without faking the IL. I like the IL in Carrara a lot, but i can’t get it to work in closed rooms :(.
Also Studio has the same problem :D. I haven’t tried in Poser but it probably has the same issue…

As far as i know at least, the problem is the closed room, but i could be wrong. Added a pic with the ceiling removed (creating an “open” room), wich looks much better IMHO. I also did the promo renders for my poses in carrara in an open space and i like the way it looks. I just would like to be able to do that in a closed room too.

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Posted: 07 December 2012 01:11 PM   [ Ignore ]   [ # 7 ]
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Here’s a closed room test I did to emulate yours. the floor is pretty dark brown, walls are a flat white.

1 spotlight at 65%
GI set at 350%

I expect the brown to bleed, but it is tricky to control.

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Posted: 07 December 2012 01:15 PM   [ Ignore ]   [ # 8 ]
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That looks pretty good, i’ll try with a darker color too.
PS: the spot in my renders is pointing straight down on the floor, dunno if it is set up that way in your render too?

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Posted: 07 December 2012 01:37 PM   [ Ignore ]   [ # 9 ]
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Did a series of renders for different lightness of the floor (all settings same as before, with the ceiling turned back on)
Color 1 = 55 40 55
Color 1 = 155 140 155
Color 1 = 215 200 215
For the darker colors there seems to be less color bleed, but as it gets lighter the il gets more colored…

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Posted: 07 December 2012 01:39 PM   [ Ignore ]   [ # 10 ]
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Your ray depth is far too high.

25 bounces? Every bounce will just add more colour and in a closed box the light will always bounce. You’ve already discovered that you need to let it escape.

Also (and this is a purely personal bias and unrelated to the colour issue) you are probably overdoing it on the object and shadow accuracy. I only go that sharp for hard edged technical excercises. For normal viewing you can get away with a lot less.

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Posted: 07 December 2012 01:54 PM   [ Ignore ]   [ # 11 ]
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Here’s one with max ray depth set to 1. I thought it would get darker, but it’s the same as 25. I guess max ray depth only affects reflections and not the GI.

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Posted: 07 December 2012 02:01 PM   [ Ignore ]   [ # 12 ]
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Elele - 07 December 2012 01:15 PM

That looks pretty good, i’ll try with a darker color too.
PS: the spot in my renders is pointing straight down on the floor, dunno if it is set up that way in your render too?

My spot was pointing into the corner.

FYI: I tried adding a hardwood floor texture map with some reflection to it -very difficult to control the room color! I am giving up, for now.

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Posted: 07 December 2012 04:11 PM   [ Ignore ]   [ # 13 ]
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Elele - 07 December 2012 11:52 AM

Thanks for the replies smile

There is a white ceiling and the room is completely closed.
Making the color less saturated actually makes things worse, seems carrara adds saturation with each bounce.
Here’s an example with the floor 255 240 255 (light purple). There room gets a lot more purple than the original floor color.
To what should i apply the ambient color? To the light?
I don’t really want to add other lights to fake IL, caus I might as well just fake the IL then.

Also added a screeny with the render settings.

Also added a screeny of the scene, to show it really is only the floor that is colored :D

have you tried to play around with the photon count? try to drop the photon count down to 2000 or 5000 and eventually increase the ambient light

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Posted: 07 December 2012 04:13 PM   [ Ignore ]   [ # 14 ]
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Hi Elele.

The only way I found to control the color for GI in an inclosed area is to setup the Irradiance map feature(Render room), and
then add or adjust textures after saving the map(similar mentioned on p.677 of PDF manual). To add; the IR map currently has a bug for animation, but should work fine for the first frame.

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Posted: 07 December 2012 06:18 PM   [ Ignore ]   [ # 15 ]
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I’m not sure what you’re expecting for results, or what you think the “problem” is.

I’m no where near an expert in radiosity, nor do I have a clue how Carrara’s version is implemented, but I think you need to step back a bit and consider what happens in the real world. As Holly accurately said, it’s not designed to be a physics emulator, and there’s no guarantee the results will accurately reflect the real world, but the results are probably closer than you might think.

First consider how lights and materials operate in the real world. If, for example (and I’m not saying this is the case you’re discussing), you have a completely white light in a completely white room shining on a red floor, the ONLY light bouncing around the room will be red. That’s because the white light hits the the floor, takes on the red color of the floor, and becomes red light, which then colors every white wall it hits with red. Even the spot on the floor hit by white light turns red.

Now, much of this depends on a lot of factors.

The properties of the floor and walls, for example. If they are non-reflective or very bumpy, etc., less light will be bouncing off the floor, and therefore the room will be darker, and, in this case, less red. The properties of the materials involved are hugely important when considering how real light will travel.

Where is the light pointing? If it’s pointing at a white wall, the “color bleed” as some seem to want to call it will be less because only reflected light, not direct light, hits the red floor first.

It’s also a function of color saturation, and relative colors of the floor and walls and light. As well as intensities.

And if the only color present in any lights or materials in your scene are, say, red, then what do you expect? Of course the light in the room will be colored red. Radiosity takes your white light from your light and bounces it a bunch of times off the red floor. Of course you’ll get a lot of “color bleed”.

Now, I’m not saying that the Carrara radiosity is correct or not correct. I’m merely saying it’s really, really complicated, and before you say it doesn’t look right you have to know what “right” is first. And I suspect it’s less a function of which dials you spin and which boxes you check than whether your expectations are in line with the real world.

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