I’m struggling to figure out how to create realistic outdoor lighting.
I’ve tried a GI spotlamp parented to Icosphere, but I’m just not happy with how that turns out - it looks obviously like fake global illumination!
So if anyone could share any tips on creating a realistic looking outdoor light setup?
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Brian
When I have tried to mimic outdoor lighting in the past I have worked with a modified GI setup with the power of the lights in the GI sphere varying (the lights in the area that the main light shines from is brighter) and also with slight coloration, lights on main shadows side with a slight blue and main lights with slight orange (or such, depends on day time) %|
Hope that helps some 
neat color trick!!!
The trick is to simulate the real life. On a bright day, you have a blue skydome (sky) and one yellowish spot/point light (sun). This is why real shadows often have a slight blue tint. The shadows from the sun have rather sharp edges. The color values have to be adjusted when the daytime changes.
When it is cloudy, the hard shadows produced by the sun disappear and all shadows become very soft because only the skydome is left.
It’s more than that. What you’re probably trying to imitate is the lighting of a professional photograph which was set outdoors. Go to the local park early in the morning and hope to find a studio photographer working there. You’ll see that he’s using a lot more than “natural light.”
Ex minimis, he is definitely starting with what God gave him, which is: - A warm red sun which is probably coming from a low angle; it’s dawn or it’s dusk. - Blue light coming from overhead, dimmer than the sun (of course), directionless but casting shadows. Thou shalt read: (the second half of…) http://download.blender.org/documentation/html/x4029.html Right now! 
Start with “Area Light” and keep reading.) But our photographer did not simply rely upon God… oh, no-siree! He or she’s got several off-camera assistants with him/her, and they’re holding reflectors made of cloth coated with a silvery or bronze coating. There may be diffusers of translucent cloth breaking up the harsh shadows from the sunlight. A lot of attention is being placed on “getting catch-lights in the eyes.” He or she is studying the viewfinder, blipping the scene with an incident light-meter (the funny one with a little plastic ball on the front, which you see every Hollywood type wearing around his neck in those ‘Making Of…’ videos that we all love), worrying about exactly how much light the “brightest” point is reflecting to the lens, versus the “darkest” one. He’s recomposing the shot, making tiny adjustments to achieve that “natural” shot, all for reasons that he can barely explain to a layman, and all so that the aforesaid layman might never notice them in the first place. 
Yessir, for reasons known only to him/her, Dr. Richard Feynman, and … you, Gentle Reader … there is a good reason for all this, and believe it or not, it does apply directly(!!) to you! :o
(Pause to let the orchestra crescendo die down…) %| Ahem. … I guess I do get carried away sometimes. 
But since we’re halfway there, shall we go-for-it? …
You see, film does not see the world as our eyes do. Not even close. And video is even more limited. Our God-given eyes scan the scene, and the amazing carbon-based computer between our earlobes assembles those scans into “our perception of” the scene. We can instantly recognize about 24 f-stops of range between “black” and “white.” Film can capture about 5, and video is even less. (After you drop the words ‘zone system’ to the film-guy, ask your friendly neighborhood videographer to explain ‘white balance.’)
Even when we are working with computer-generated video data, the principles are the same. We’re constructing a single image which the viewer will then scan with his/her eyes. We have to achieve the illusion that this image is remotely similar to what the viewer would perceive by scanning the original scene with those same eyes.
Ponder this: look at the video scene in front of you right now. On my screen it’s a warm brown and the text appears in crisp black-on-white. Now, turn the monitor off! In a few moments, you’ll see a uniform dark-gray field in front of you. But it doesn’t seem as “dark” as the “black” field where this very piece of text appeared just moments before, now does it? When you turn the tube back on, the area where this text appears now seems to be darker than the turned-off screen surface seemed to be, does it not?
This effect is achieved by the relative contrast between the areas which your eye perceives as “brown” and those which it accepts as “infinite black.” Film has a similar phenomenon. All media of this sort does… all media which relies upon transmitted light (from the screen surface) to emulate reflected light (from the real world objects we seek to depict). The printed-page, by comparison, is completely different… right down to its RGB vs. CMYK color-space. You can really get lost in the physics at this point, and not being a physicist myself, I must pull back. But you get the idea. You run smack-dab into the same physics that still photographers and cinematographers do. You can get away with it on Alpha-Centauri, but not in Boston.
If you want to reproduce shots like that, you need to reproduce lighting like that. The local photo store should carry a number of books which tell photographers how to achieve that. You’ll frankly be amazed at how much a photo which your eye accepts as “real,” has in fact been altered before it’s even been shot.
Joe Sixpack isn’t the slightest-bit aware of these arcane issues, and we’d like to keep him that way. We’d like him to [pay admission to… 
] see our movies and “accept them as real, ‘of course’” and think nothing of it. But we[/u] have to think of them, just to be sure that our images “turn out right” on-screen. We have no choice.
If you have the time, call up your local photo-pro and offer to hold the scrims and reflectors for him/her, [i]gratis. Show up early, do what you’re told, and watch closely. You’ll learn a helluva lot, and you’ll see the morning at a beautiful time when most people are asleep (or the evening when most blokes are watching TV), and have a lot of fun. But most of all, you’ll learn a helluva lot that applies directly to “computer” graphics.
(Keep this in mind: If we are taking the viewer to Alpha-Centauri, then of course we devise the rules. But if we’re taking him or her to the real world, in the present or the past or in the future, then “computer graphics is just graphics, which happen to be built using a computer.” The same principles of good graphic design which would apply to a photo, or a film, or even a painting, apply equally well to us. Avail yourself of their books and their experience.)
sundialsvc4, thanks a lot for the very correct treaty!
Thanks for the suggestions - I’m currently using this simple setup:
Hemilamp, energy 0.9, RGB 0.8,0.9,1.0
and a shadow only spotlight, energy 0.9, RGB 1.0,0.95,0.9
Also added a world with ambient settings of RGB 0.3,0.3,0.25
Seems to give good results so far
again, thanks for the informative posts!
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Brian