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Indirect light in closed room
Posted: 08 December 2012 06:20 PM   [ Ignore ]   [ # 61 ]
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evilproducer - 08 December 2012 05:03 PM

If you’re trying to realistically light an interior room why wouldn’t you consider setting the lights up realistically as well. In most cases that wouldn’t be spotlights..

Okay, so all of this discussion of lampshades and spotlights and translucency and frosted glass comes down to your belief that you should model your lights realistically? Umm, okay, guess nobody can argue with that.

I’m scratching my head trying to figure out what that has to do with the topic we’re discussing (y’know, radiosity and what everyone is calling “color bleed”), but I’m sure all of the scientists here can sort that out.

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Posted: 08 December 2012 06:22 PM   [ Ignore ]   [ # 62 ]
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Where can i adjust it then?
...I don’t know what a shadow buffer is :D

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Posted: 08 December 2012 06:27 PM   [ Ignore ]   [ # 63 ]
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Elele - 08 December 2012 06:18 PM
JoeMamma2000 - 08 December 2012 06:06 PM
Elele - 08 December 2012 04:56 PM
JoeMamma2000 - 08 December 2012 04:53 PM
Elele - 08 December 2012 04:41 PM

Is there a way to get rid of these harsh transitions (see pic)? .

Enable soft shadows for your lights. And disable/set to zero all ambient light.

Soft shadows won’t work I think, since they aren’t really “cast” shadows but the shadows from the geometry itself.

I think you’re mistaken….

Really? Do I need some special setting?
All I get when using soft shadows is this (see pic)
The soft shadow doesn’t alter the shadow of the cube itself, only the “cast” shadow.


Are you talking about how deep black the shadows are, or something else? because to me, it looks like it’s behaving as it should. The light doesn’t cast a shadow, something blocking the light casts the shadow, just as in real life. If you’re talking about the edges of the cube defining the shadow on the shaded side of the cube, that’s to do with the sharp edges. If the blur in the second picture is to strong, lower the radius of the light.

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Posted: 08 December 2012 06:31 PM   [ Ignore ]   [ # 64 ]
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Elele - 08 December 2012 06:18 PM

Really? Do I need some special setting?
All I get when using soft shadows is this (see pic).

AHHH, okay, when you said “sharp transitions” you didn’t mean “cast shadows” ?

The reason why the cube in your example has a black, unlit side is because there is no light there. And as a scientist you know that light only travels in straight lines, so there’s no way your directional light source could illuminate that back area on its own. There would have to be either another light source, or light bouncing around the scene for some reason.

That’s not the job of the single light source in your scene, though. It’s the job of either a radiosity simulator, or the artist who places a simulated bounced light source behind the cube so that light bounces into that area and provides some illumination.

Which is why when people “fake GI” they add not only a main light source (or multiple primary light sources), but the also add bounce light sources to simulate the light from those primary lights bouncing on the walls, floors, etc.

 

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Posted: 08 December 2012 06:36 PM   [ Ignore ]   [ # 65 ]
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JoeMamma2000 - 08 December 2012 06:20 PM
evilproducer - 08 December 2012 05:03 PM

If you’re trying to realistically light an interior room why wouldn’t you consider setting the lights up realistically as well. In most cases that wouldn’t be spotlights..

Okay, so all of this discussion of lampshades and spotlights and translucency and frosted glass comes down to your belief that you should model your lights realistically? Umm, okay, guess nobody can argue with that.

I’m scratching my head trying to figure out what that has to do with the topic we’re discussing (y’know, radiosity and what everyone is calling “color bleed”), but I’m sure all of the scientists here can sort that out.


It has a lot to do with it. I’m currently rendering a scene with a translucent sphere around a bulb light. The room walls are white, the ceiling is white and the floor is a reflective brown color. So far the render doesn’t have all the reflected color bleed that the OP was concerned about. So if this works to mitigate the color bleed, then my point about trying to mimic real world lighting in a simulation that tries to mimic real world light bounce is correct at least on a basic level. Is that enough on topic for you?

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Posted: 08 December 2012 06:56 PM   [ Ignore ]   [ # 66 ]
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JoeMamma2000 - 08 December 2012 06:31 PM
Elele - 08 December 2012 06:18 PM

Really? Do I need some special setting?
All I get when using soft shadows is this (see pic).

AHHH, okay, when you said “sharp transitions” you didn’t mean “cast shadows” ?

The reason why the cube in your example has a black, unlit side is because there is no light there. And as a scientist you know that light only travels in straight lines, so there’s no way your directional light source could illuminate that back area on its own. There would have to be either another light source, or light bouncing around the scene for some reason.

That’s not the job of the single light source in your scene, though. It’s the job of either a radiosity simulator, or the artist who places a simulated bounced light source behind the cube so that light bounces into that area and provides some illumination.

Which is why when people “fake GI” they add not only a main light source (or multiple primary light sources), but the also add bounce light sources to simulate the light from those primary lights bouncing on the walls, floors, etc.

 

My art lingo isn’t really top notch, I’ll try to explain what i mean:

The top surface of the cube is the brightest, then the right and then the back.
The light on one surface is pretty evenly distributed though and each surface is lit differently, hence creating the “harsh transitions” i was talking about.
Is there a setting for soft shadows that can soften the difference in intensity between the surfaces of the cube?
Relating to Holly’s render, is there a setting she can turn on/off in the soft shadows to reduce the “harsh transitions”, or does she need to add more lights to do that?

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Posted: 08 December 2012 06:59 PM   [ Ignore ]   [ # 67 ]
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evilproducer - 08 December 2012 06:36 PM

So if this works to mitigate the color bleed, then my point about trying to mimic real world lighting in a simulation that tries to mimic real world light bounce is correct at least on a basic level. Is that enough on topic for you?

Yes, of course, if 80% of the room is illuminated by direct white light from a bulb, and 20% is by bounced light off a colored floor, then obviously the room illumination will have less color than if all of the room illumination is from colored bounce light off the floor. If that’s an important revelation for discussion, then I’ll stand aside. I figured it was obvious. Maybe not. 

 

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Posted: 08 December 2012 07:07 PM   [ Ignore ]   [ # 68 ]
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Elele - 08 December 2012 06:56 PM


The top surface of the cube is the brightest, then the right and then the back.
The light on one surface is pretty evenly distributed though and each surface is lit differently, hence creating the “harsh transitions” i was talking about.
Is there a setting for soft shadows that can soften the difference in intensity between the surfaces of the cube?

I think you have a basic mis-understanding about light and how it travels, as well as materials and surfaces and how they interact with light.

If a uniform, directed light beam illuminates a surface (eg, a side of your cube), then that entire surface will have that same level illumination. Try it sometime in a dark room with a bright and uniform flashlight.

The spotlight in your scene is perfectly uniform, the surfaces on your cube are perfectly uniform, there is no bounce light in the scene, and there are no other shadows or objects to cast shadows on the cube.

The only way you can get a variation in illumination on any surface is if something causes it. Either your light source becomes non-uniform or something else in the scene causes some variation.

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Posted: 08 December 2012 07:07 PM   [ Ignore ]   [ # 69 ]
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Elele - 08 December 2012 06:22 PM

Where can i adjust it then?
...I don’t know what a shadow buffer is :D

Hi, yes, sorry….

Click on your light and the click on the EFFECTS TAB. Under Shadows you should see a drop down list that allows you to select SHADOW BUFFERS. They are a kind of “soft shadows” that calculate very fast but are not always practical because they do not respect an object’s shadow on itself (for instance the shadow inside a figure’s nostrils or inside their mouth)...

Everything is a tradeoff. Some lights have advantages and weaknesses…. Also try Tube Lights and Shape Lights (with and without Shadow Buffers), which also have their quirks, but can look more directionless, like Ambient Lights but with shadows…

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Posted: 08 December 2012 07:21 PM   [ Ignore ]   [ # 70 ]
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Here’s one with the shadow buffer (thanks :D). It does create a little gradient on the right side of the cube (red arrow), but I don’t see how you could rely on that to get better renders, it looks more like an error to me…

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Posted: 08 December 2012 07:29 PM   [ Ignore ]   [ # 71 ]
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Here’s some test renders I did. The IL was set to it’s default. For this series, I placed a sphere with white, translucent shader over both a spotlight and bulb light. I rendered a version for each with the sphere and without the sphere.


The first image is with the spotlight and no sphere. The second is the spotlight with the sphere. The third is the bulb with no sphere and the fourth is the bulb with the sphere.


Edited to add that I used soft shadows on the light with light radius of .5 ft.

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Posted: 08 December 2012 07:34 PM   [ Ignore ]   [ # 72 ]
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Elele - 08 December 2012 07:21 PM

Here’s one with the shadow buffer (thanks :D). It does create a little gradient on the right side of the cube (red arrow), but I don’t see how you could rely on that to get better renders, it looks more like an error to me…


Shadow buffers are meant to mimic raytraced soft shadows. They’re designed for speed. All things being equal, raytraced soft shadows are more accurate. Shadow buffers can be can be useful, but there are a bunch of caveats, some of which Holly mentioned.

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Posted: 08 December 2012 07:36 PM   [ Ignore ]   [ # 73 ]
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JoeMamma2000 - 08 December 2012 06:59 PM
evilproducer - 08 December 2012 06:36 PM

So if this works to mitigate the color bleed, then my point about trying to mimic real world lighting in a simulation that tries to mimic real world light bounce is correct at least on a basic level. Is that enough on topic for you?

Yes, of course, if 80% of the room is illuminated by direct white light from a bulb, and 20% is by bounced light off a colored floor, then obviously the room illumination will have less color than if all of the room illumination is from colored bounce light off the floor. If that’s an important revelation for discussion, then I’ll stand aside. I figured it was obvious. Maybe not. 

 


And yet everybody kept talking about spotlights and no other light types except Holly in her example. So yeah, maybe it was obvious, just not to everybody.

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Posted: 08 December 2012 07:47 PM   [ Ignore ]   [ # 74 ]
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JoeMamma2000 - 08 December 2012 07:07 PM
Elele - 08 December 2012 06:56 PM


The top surface of the cube is the brightest, then the right and then the back.
The light on one surface is pretty evenly distributed though and each surface is lit differently, hence creating the “harsh transitions” i was talking about.
Is there a setting for soft shadows that can soften the difference in intensity between the surfaces of the cube?

I think you have a basic mis-understanding about light and how it travels, as well as materials and surfaces and how they interact with light.

If a uniform, directed light beam illuminates a surface (eg, a side of your cube), then that entire surface will have that same level illumination. Try it sometime in a dark room with a bright and uniform flashlight.

The spotlight in your scene is perfectly uniform, the surfaces on your cube are perfectly uniform, there is no bounce light in the scene, and there are no other shadows or objects to cast shadows on the cube.

The only way you can get a variation in illumination on any surface is if something causes it. Either your light source becomes non-uniform or something else in the scene causes some variation.

As far as I know the difference in intensity between the surfaces of the cubes comes from the angle they make with the light beam.
The top of the cube has the largest angle (closest to 90°), hence the light is spread over a smaller area resuling in a brighter side, no?

Now how would you add lights to a complex model like the one Holly used, to fake IL and get smooth gradients? I think it would already be pretty difficult for a simple cube…

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Posted: 08 December 2012 07:47 PM   [ Ignore ]   [ # 75 ]
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evilproducer - 08 December 2012 07:36 PM
JoeMamma2000 - 08 December 2012 06:59 PM
evilproducer - 08 December 2012 06:36 PM

So if this works to mitigate the color bleed, then my point about trying to mimic real world lighting in a simulation that tries to mimic real world light bounce is correct at least on a basic level. Is that enough on topic for you?

Yes, of course, if 80% of the room is illuminated by direct white light from a bulb, and 20% is by bounced light off a colored floor, then obviously the room illumination will have less color than if all of the room illumination is from colored bounce light off the floor. If that’s an important revelation for discussion, then I’ll stand aside. I figured it was obvious. Maybe not. 

 


And yet everybody kept talking about spotlights and no other light types except Holly in her example. So yeah, maybe it was obvious, just not to everybody.

I did, but everyone missed it…or fell asleep while I was banging on about other stuff.

Nothing is too obvious to mention. That’s at the heart of many moments of revelation.

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