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Indirect light in closed room
Posted: 08 December 2012 04:27 PM   [ Ignore ]   [ # 46 ]
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RoguePilot - 08 December 2012 03:59 PM

To answer one of your questions, in a 100% sealed room with a constant light source the photons would continually accumulate until it was filled entirely with light. This is clearly an impossibilty and actually impossible to observe..

No, I wasn’t angry, merely frustrated. As I usually am in this forum.

Thanks for the description of what happens on a photon by photon level, but I’m not sure what that adds to the discussion.

Fine, in the real world, light energy dissipates, so the room never fills with infinite light.

Now, back to the issue at hand…

 

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Posted: 08 December 2012 04:34 PM   [ Ignore ]   [ # 47 ]
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holly wetcircuit - 08 December 2012 03:16 PM

Here is an example of why I don’t use GI much….

The top image uses GI to “fill in” the lighting. This is pretty much the default setting (100% Indirect Lighting, Interpolation = 20%, 5000 photon count…) If you click the image you can see “ashiness” in the lighting so this initially has a *wow* look of GI, but on closer inspection this is not acceptable…. I could turn off Interpolation and step up the photon count, but this image already took almost 2 hours to render….

Now look at the bottom image. This is where I “faked” GI. The scene uses 6 Ring Lights at the top of the columns. All I did for the “fake” GI is duplicate the lights in the scene, cut their brightness in half, and drop them down to the floor at the base of the columns…. Now there are twice as many lights in the scene, but it renders in 2min 45sec. Go ahead and look at the image large. It has no ashiness, but the lighting is very close… nearly identical… But with a few minutes extra work with the lighting in my scene, I have saved 1hr 57min of rendertime….

GI is actually the “fake” method to get good lighting. As you can see it comes at a ridiculous cost in rendertime.

You can really see the difference in noise throughout the picture. The one without GI is pristine.

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Posted: 08 December 2012 04:41 PM   [ Ignore ]   [ # 48 ]
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That looks pretty darn close smile

Is there a way to get rid of these harsh transitions (see pic)?
That’s one of the main problems I have when I try to fake GI: Due to the relatively small amout of lights, some parts of the geometry don’t catch enough light compared to other parts. The GI bounces compensate for that, but i don’t know how to do it another way.

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Posted: 08 December 2012 04:53 PM   [ Ignore ]   [ # 49 ]
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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.

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Posted: 08 December 2012 04:56 PM   [ Ignore ]   [ # 50 ]
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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.

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Posted: 08 December 2012 05:03 PM   [ Ignore ]   [ # 51 ]
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JoeMamma2000 - 08 December 2012 03:25 PM
evilproducer - 08 December 2012 11:39 AM
evilproducer - 08 December 2012 09:00 AM

Just a thought here, but in a room lighting situation, generally you don’t use spot lights which are very focused and bright. You usually use a bulb with a translucent shade of some sort. What happens if you assume it’s a ceiling light, place a translucent light shade below it and then see what you get?


Just quoting myself as it was the last post on the previous page and may get overlooked in the coming crap-storm. wink


Just to reiterate though, how many people really light their rooms with spotlights?!?

Apparently you think that was such an important point that you need to re-iterate it, so I’ll address it.

I could give you a long list of lights used in room lighting situations that act like spotlights. In fact in my living room I use what are called “track lights”, which are a row of small, narrow beam spots mounted in a metal track you can move and adjust. They are used for accent lighting, and in my case that’s all that lights the room.

Also, most lighting fixtures and lamps are set up to focus a bulb so that it acts pretty much like a spotlight. You even gave an example, where a shade is used to focus the light. Because in fact a bare bulb in the room hurts your eyes, so nobody uses it. So really the vast majority of lights used in a room situation are some form of directed light, not a bulb.

Just take a look at the IES profiles of many of the lights provided by manufacturers and you’ll see that in fact there are many, many lights with spot-type profiles, either because of the bulbs themselves or the reflectors they are mounted in.

However I’m not sure what that all has to do with what we’re discussing….

Are you saying that if you use a spotlight in your simulation, which you’re not used to seeing lighting a room in real life, then your results might look weird because you’re not used to seeing it in real life? I dunno, but I don’t think that’s the issue the OP is having. I think it’s more about expectations.

It is about expectations, you’re right. But it’s also the light. Track lighting not-withstanding, most lamp shades are not opaque, which is why I made a point of putting translucent in my post as well. End table lamps usually have a cone shaped paper or fabric covered paper shade which does direct a lot of light down and also up through the bottom of the shade. With most shades I’ve observed, the shades are also allowing light through the sides and at the same time diffusing it.

Ceiling lights are another good example. Many times they’ll have a frosted glass shade or globe around them. The non-globe style does reflect light back to the ceiling and also out the sides depending on how deeply dished it is, but they also let a lot of light through the bottom which will also diffuse it. A globe of course will let light out in all directions, just diffuse it even more than a bare bulb.

All my examples direct light, but also allow for substantial omni-directional light bleed, which spotlights don’t. Maybe your track lights are different and have translucent housings, so you see it differently. I don’t know.

My point is, that Carrara does take the translucency channel into consideration when rendering and in fact I’ve read in the manual that Indirect Lighting is supposed to give the best results for rendering translucency and SSS. 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.


As Holly pointed out, Carrara’s an art program and not a simulator, but real life lighting conditions are also a factor to consider when using a lighting model that is supposed to simulate bounced light. Personally, I avoid using it due to the time hit.

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Posted: 08 December 2012 05:10 PM   [ Ignore ]   [ # 52 ]
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BTW, I tried with the bulb and messing with translucency (and the photon count and the gamma :D), but so far iI haven’t gotten it to work.
The translucency thinghy is tricky though and i’m not sure i really understand it yet. More testing is needed!!! (Like Rogue, I’m a fellow scientist in case you hadn’t noticed :D )

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Posted: 08 December 2012 05:16 PM   [ Ignore ]   [ # 53 ]
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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.


Sometimes I’ll render a low res. image to see how the lighting looks in the shadows. I usually do this with the Skylight and in outdoor scenes, not with Indirect Light and indoors, but it could help you with light placement.


Also, I know Joe hates ambient light, but used with caution it can also help lightening dark areas. The problem most people have with it, is they leave it at the default 20% brightness and the white color chip. You need to adjust it per scene, so in my opinion, I wish it defaulted to off, instead of on.

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Posted: 08 December 2012 05:25 PM   [ Ignore ]   [ # 54 ]
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I haven’t gotten to the light setup yet since i can’t even stop a single light from coloring the entire room.
I don’t really like to use ambient light in most cases since it lights everything evenly and doesn’t really look right to me… but i did already try it in this case though :D

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Posted: 08 December 2012 05:45 PM   [ Ignore ]   [ # 55 ]
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Playing around a bit with lights, so if I get a good result I’ll post the settings.

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Posted: 08 December 2012 05:48 PM   [ Ignore ]   [ # 56 ]
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Has anyone tried IR maps yet? You can add a slight bit of color needed to a floor or wall shader(s) etc. without changing the GI settings or light color. Render to save the IR map. Then add or adjust other room textures and render again using the saved map(IR maps should also be much faster for testing). Not a total solution but atleast it can fake(or adjust) the way color adds to a room.

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Posted: 08 December 2012 06:06 PM   [ Ignore ]   [ # 57 ]
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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….

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Posted: 08 December 2012 06:08 PM   [ Ignore ]   [ # 58 ]
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tbwoq - 08 December 2012 05:48 PM

Has anyone tried IR maps yet? You can add a slight bit of color needed to a floor or wall shader(s) etc. without changing the GI settings or light color. Render to save the IR map. Then add or adjust other room textures and render again using the saved map(IR maps should also be much faster for testing). Not a total solution but atleast it can fake(or adjust) the way color adds to a room.

Is the IR map the same as the IL Layer from multipass renders? I’ve been playing around with that, caus i can’t open the IR map in other programs.

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Posted: 08 December 2012 06:18 PM   [ Ignore ]   [ # 59 ]
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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.

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Posted: 08 December 2012 06:20 PM   [ Ignore ]   [ # 60 ]
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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….


You’re right, I think Elele is thinking of shadow buffers.

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