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Old 24-02-2003, 08:26 PM   #1
Zytrex
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Exclamation GLOBAL ILLUMINATION DISCUSSION

Am I the only person getting fed up with GI because of how difficult it can be to get even barely acceptable results without ending up with horrible rendering times? The movie and game industry has been getting along without GI for a very long time because it is so slow. I have some scenes that take more time to render than it took to design. That, to me, is quite disgusting.

There are some situations where GI can help the design process. For instance, if one is modeling a complicated character or vehicle, a well set up skylight-style GI can help identify problems in the mesh. But for a final render, no pun intended, I like to see some depth and shadow, not just some dark areas where the faces are close to each other and at an angle facing each other, or close to it. In other words, skylight-style GI is out for final renders as far as I'm concerned.

So how about full blown radiosity or something in-between? Well, if it's of any quality, the render times will blow you away, even if you are only doing a still. Animation? Out of the question! I read an article about Final Fantasy: The Spirits Within. In it, people working on the project said that the average render time for a final frame in the movie was 90 minutes. And when I say final frame, I mean all frames that were rendered separately and then composted together into one frame. So that's 90 minutes, on their PIII Linux machines, for several different frames that are turned into one frame in the movie. I have a P4 2.53 with 512MB DDR and I have a scene where, after about 40 minutes of calculating radiosity, takes about 150 minutes to render. That's a total of 190 minutes for a single frame. Sure, if nothing in the scene changes, I don't have to recalculate the radiosity, but what kind of animation has no movement? And my room is very simple compared to the scenes in Final Fantasy. I just have six walls, three windows, and two tables! And what's more, this is just my scene. I've read things on here where people spend 4 to 8 hours rendering a single frame.

I remember back to before I had access to global illumination. I would render an animation while I slept. There would be 8 or so lights for well rounded lighting and about 400 frames. When I got up in the morning, it would be all done. Remember that scene of mine that would take 190 minutes to render? Before I added GI, I had a whole bunch of lights in there to get it looking good and the whole thing would render in about 15 minutes!

There are many ways to make light appear to bounce around a scene. I wish I knew some of the tricks to faking GI. Sure, you can put lights of colors corresponding to colors in the scene near geometry that should be receiving that color through bounces of light from other geometry, but that isn’t nearly as easy as it sounds. At least, it isn’t for me. If anybody wants to comment on why they like or don't like GI, please post. Hey, if you think GI is great, tell me! I know it sounds like I hate GI, but I really just hate that it’s slow. Having used it a lot, I am aware of how great the results can be. So now I address those of you out there who have been setting up good lighting in a scene without wasting time with global illumination. Please, tell us how you do it. Even better, show us. Thank you!

If this thread works out and people start posting, perhaps the admins will consider making this a sticky thread? I'm sure the many people out there who have GI but are sick of the render times and the many more people out there who don't have GI at all would love a thread about making realistic lighting for a scene!
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Last edited by Zytrex; 26-02-2003 at 05:31 PM..
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Old 25-02-2003, 01:53 AM   #2
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.... .... .... .... .... .... or not.
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Old 25-02-2003, 03:22 AM   #3
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Personally I use GI mostly when I want to render a single object, so it shows up better. For scenes I prefer to use common lights, lots of them sometimes, 2 or 3 dozens are normal.
Each scene is different and needs a different approach to how it is iluminated, for example in a particular scene I ended up ligthing things using the SHADOWS of some lights, strange as it may seems it worked very well.
As i said each scene needs a different lighting, but outdoors scenes look more or less the same, a main light (Sun or Moon) a sky light and some light bounced from the ground. What I do is create three rings of omni lights, 12 for each one. One ring of bluish lights, the larger and placed higher than the rest; that will be the skylight, a second ring, usually smaller and bellow the first one, the lights have the same colour as the main light, although a bit washed out or mixed with the sky light. That makes the fill light. And the third is another ring placed bellow the ground level and the omnis have the average colour of the ground. Then I add the main diretc light, plus a few secondary spots or omnis. All this makes quite nice, soft lighting and keeps render times reasonably short.
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Old 25-02-2003, 10:24 AM   #4
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Well Goig!

I like that idea. How large are the rings compared to the scene? Like, does the diameter of the ring go all the way from one side of the scene to the other? The third ring being the average color of the ground, I assume that is to simulate light bouncing off of the ground? And the blue lights; are they supposed to be the lighting from the blue sky? I'm just trying to clarify because some people like to use a blue tint in night time scenese and I want to be sure of what you are talking about.

Also, what was that about shadows lighting objects?
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Old 25-02-2003, 12:12 PM   #5
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It just looks so nice

Here's an ooold scene that I never finished (like most).
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Old 25-02-2003, 12:44 PM   #6
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Well, like most things around any 3d package GI is just a tool, and sometimes it useful and sometimes it isnīt...
I do agree however in that thereīs been an overuse of GI lately and most cases it was not justified! Most people (including me)usually smack a skylight and a spot and call that a lighting scheme, and the truth is that it does not look bad at all even tough it does wash up the scenes a lot.
But mostly I think itīs just the alure of the new toy...as more efficient GI calculation methods come up, with the aid of the ever increasing power of desktop PCs, GI sudently became available to almost everyone, and they all wanna have a go at it I guess.
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Old 25-02-2003, 12:52 PM   #7
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I dont agree at all. GI gives you much better results than non GI. If an image looks washed out , tweak it. Being skilled with GI gives much nicer images than being skilled with normal lights. If it looks bad with GI it's just because it needs tweaking/changing, like with everything.

Oh and just to avoid misunderstandings for me 'more realistic'=better

(unless it's completely abstract or intensely impressionistic of course, but then that's per definition )
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Old 25-02-2003, 10:34 PM   #8
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Kit: I agree with you completely.


Incitatus: I do not think that GI gives you much better results than with normal lights if you have good skills with normal lights. What GI does is make it easier to set up the lighting in a scene. You place a few lights for lamps and things like that, and you let GI do the rest. I think any person can look at a scene and figure out where light is going to bounce around. It might be a little tedious, but the results can be very good.
  I do believe that GI provides better results, not much better, but better, however, at a horrible penalty in rendering time. For GI to actually look good, where there are not artifacts all over the place, dirty shadows, and grainy lighting, the rendering times increase around ten times or more, depending on how complicated the scene geometry is. That might be okay for a still, if you don't mind waiting over night to see the results, but as I said before, it's completely impractical for animation.
  I know I've referenced this before, but I still think it's a perfect example. The lighting in Final Fantasy: The Spirits Within was perfect. The people working on the lighting had been working their whole career without practical use of GI and knew how to light a scene realistically. Here's a question for you: It is very common practice to render different parts of a scene separately and then composite them later. This gives the artist much more control over how a scene looks. In a situation like that, I don't even see how GI could be used? If only some of the geometry is there, how is there supposed to be a radiosity solution?
  I think that GI tends to take control away from the artist. When you use normal lights, you can get it to look exactly how you want, if you have the skills; but with GI, the computer decides how it should look. Other than making some surfaces more accepting to color bleeding and reflected light, and of course tweaking the endless number of quality controls, there isn't a whole lot you can do to customize the way GI lights a scene. Unless, of course, you dim down the GI and start adding normal lights to do some of the fine work to make the scene look just how you want, of course then you're half way to just faking GI all together, but you're still cursed by the horrible rendering times.
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Old 26-02-2003, 03:30 AM   #9
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Zytrex, usually I make the rings one half or twice as big as the scene, in example, if the whole scene fits in a sphere of 100 units of radius then I make the rings 150-200 units in radius.
As for the blue colur of the lights, yes is to fake sky light, I use the same colour of the background sky, but more towards white, to avoid too much colour.
I agree with you about the abuse of GI, and how traditional lighting is disregarded; as far as I can tell no 3D artist would get anywhere without knowing how to set up a proper lighting scheme.

Hereīs an example of a rendering (well a composite of 3 renderings) done with the method I described, looks GI or what?
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Old 26-02-2003, 04:55 AM   #10
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That looks excellent. Not just the lighting, the model too. In my opinion, that looks better then what one would get from a skylight. With this pic, you can actually see shadows, but with skylight, it just gets dark where geometry faces are close to facing each other. And with radiosity, you would have to add walls to make the light bounce around, unless you had a lot of light sources which kind of defeats the purpose, you know what I mean? What kind of shadows are you using?
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Old 26-02-2003, 01:24 PM   #11
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i kno NOTHING about lighting ...


but Goig that looks great .... ever thought of writing a tutorial on it???
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Old 26-02-2003, 02:41 PM   #12
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Addendum: donīt get me wrong, I do belive that GI are one the greatest things to happen to CG in a long time, and I belive that as PCs develops we will all be probably be using GI almost exclusivly since rendering times will go down dramaticaly (hopefully). My only complain is that most people just use the standard skylight+1 spot even for final renders and as most things that become standarized, it looses itīs edge... it becomes standard ( AKA boring!).
I have to disagree with you Zytrex when you say that GI takes control away from artists however. I think that with a good GI program you can still have full contrtol over the lighting.... besides I love having those light rays bounce around and those color bleeding effects are just yummy!
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Old 26-02-2003, 03:21 PM   #13
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I still don't agree zytrex you are comparing simple GI with advanced normal lighting setups.
Anyone can place a spot and a skylight just as anyone can make a basic 3point lighting setup. The trick is to learn to use GI. In reality the light doesn't come from all directions at the same intensity, therefore using a skylight like that is simply bad use of GI.

btw lighting for an animation doesn't need to be as precise as for a still, the brain of the viewer does most of the work in an animation.

And I'm sure if the makers of final fantasy had had the oppertunity to use GI they would have jumped at the chance.

Look at the shadow of the top left leg of the bed in my scene, it has a pefectly nice shadow -> GI
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Old 26-02-2003, 05:30 PM   #14
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Incitatus and Kit: I think we agree with eachother more than you realize. I agree that skylights are very simple types of GI. I agree that full blown radiosity can have excellent results. I do think, however, that GI can be faked a little easier than most people think. Even though light bounces around a room in different amounts in different colors, a person can still look at a scene and get a pretty good idea of where to put lights, what intensity they should be, what color they should be, and what their diffuse/specular/shadow options should be, and get pretty good results. Getting back to agreeing, I think radiosity can be fine for stills as well. It is certainly true that in animation, since the camera isn't looking at the same spot for long, it isn't as important that that spot looks perfect.

Now let's get back to what I would like this thread to be for: How do you people out there set up your lighting? Do you have any tricks you use for certain effects? Let's open it up to GI too. What software do you use? Have you found any shortcuts to decrease render times? For increasing quality? Wusup?
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Old 26-02-2003, 09:49 PM   #15
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Nice topic Zytrex, I'll make it sticky as you asked. I think the GI vs traditional setup debate is one we should look into. Personally I can be very lazy at times & the whole skylight + 1 spot thing is a quick & easy fix for previewing scenes. For final renders I still use GI/skylight, but I tend to use a main key & also a rim light, so essentially I'm just using the skylight as a fill light in a 3 point setup. I also ALWAYS play with a lot of the settings - light colour, shadow colour, shadow density, light multiplier, hotspot & falloff, soften diffuse edge & contrast etc etc, even for preview renders. So it does go to show I think that learning the basics still applies to GI.
btw, a good skylight for max 4 & 5 (yes I know 5 has a built in one but this is faster & good,) can be found here: http://home.wanadoo.nl/r.j.o/skyraider/e-light.htm
or
http://home.wanadoo.nl/r.j.o/skyraid...ad/e-light.zip
It also accepts bitmaps for image based lighting.
(If you ask nicely Jenn might put some bitmaps she made for it up for download.)
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