A brief summary of lighting

[leigh]

Cool summary, Zero :applause:

[Soeren Nielsen]

very nice stuff ZeroNeuro :)

Now explain to people what good you can do with a lightrig, and how you can set one up effectively :) Ill let you do the talkin ;)

[Crapstick]

Originally posted by ZeroNeuro
In the real world, a shadow’s color is the exact opposite color of the light that casts it.

Great summary indeed:thumbsup: :thumbsup: , but are you sure about that bit ??

[lazzhar]

Nice. Just i want to say a word about the color of shadows.
In photorealistic rendering , i think you should leave your shadows as they are (black). In most cases, shadow is coming from the key light, and you add exra lights as fill lights to lite the surfaces that dont receive light. If you change the shadow color i guess you should get a difference between the lighting of this surfaces. As far as i know, the parts surfaces that receive shadows should only get light from the fill lights.

[ZeroNeuro]

Its part of Leonardo DaVinci's color theory... hehe... And I'm not talking about a huge transition with the shadow color. Just a slight coloration. So the shadow would still be almost black, just a hint of the complimentary color.

Originally posted by Crapstick
Great summary indeed:thumbsup: :thumbsup: , but are you sure about that bit ??

[Crapstick]

well, if it's good enough for Leonardo... ;)

[lazzhar]

Originally posted by ZeroNeuro
Its part of Leonardo DaVinci's color theory... hehe... And I'm not talking about a huge transition with the shadow color. Just a slight coloration. So the shadow would still be almost black, just a hint of the complimentary color.

You are right. I've just got the feeling that it could make confusion when you're talking about adjustig the color of shadows. However, you could get the complimentary color of the shadow area by just giving the fill light the opposite color of the key light. This give better result and avoid having an unatural lighting.
Anyway i liked your contribuation. It's really helpfull for us.

[CourtJester]

Originally posted by ZeroNeuro
Its part of Leonardo DaVinci's color theory... hehe... And I'm not talking about a huge transition with the shadow color. Just a slight coloration. So the shadow would still be almost black, just a hint of the complimentary color.

This effect is due mainly to the human eye's ability to "white balance"... if the dominant light is orange and the environment is otherwise neutral, the shadow will take on a complementary (bluish) tinge. (For ships and giggles, try wearing red glasses outdoors for ten minutes and then walk indoors and take them off.) Same effect with white balancing a video camera.

I have found that I will only color the shadow directly if my enviro lights don't quite do it even though they are working for eveything else.

Overriding that effect gives unnatural, decidedly alien results... not always a bad thing. Ever notice that shadows on Mars images are as red as the light?

[Filmmky]

Originally posted by ZeroNeuro
Shadow color is also important. I hardly ever use a black shadow. The only time I used a black shadow is when I want a really dark and cool scene. In the real world, a shadow’s color is the exact opposite color of the light that casts it.

Hey ZeroNeuro,

Cool article man. I would like to take the opportunity to disagree with your statement about shadows though. In my experience I have found that shadows are the absence of light and therefore does not have an inherent color. It just so happens that in CGI we are given control of the shadow as a separate entity from the light casting it. Though that gives the artist more creative flexibility it also opens the door for misconceptions. Let's evaluate an example:

Say we have a sphere being lit by a yellow KEY light from the right and a blue FILL light coming from the left. The shadow from the KEY light will appear blue not because blue is the opposite color to yellow, but rather because the FILL light is blue. In the shadow from the KEY light there's complete absence of yellow, therfore the only light illuminating that region is the blue FILL light, and that's where the blue comes from.

Daylight situations are a perfect example of this fact. In a sunny day, and object's shadow from the sun will appear blue because light from the blue sky is filling it. In a overcast day the same shadow will appear to lack any blue.

So in short, instead of coloring your shadows I would leave them black and make sure that the rest of your lights have the correct colors to achieve the look you desire.

Cheers,

Filmmky

[jmBoekestein]

What about using skylights and HDRI ambient skydomes for filling in color on black/uncoloured shadows. And for instance bounced light/photon regathering. In your colorcard for colourtemp. You only have red to blue with intermediate oranges. Why bother with anything else, blue skylight, orange primary light. I think it even works with red sunsets, though indeed I do see a bit of green/turqoise then.:thumbsup:

PS/edit: There was a scientist a while back theorising on the existence of parallel universes. He had set up an experiment to "establish probability" of his theory. In his setup wave patterns of photons, that couldn't be proven to be there in our actuality, were influencing the measured photonic energy-waves. Taking into account that wave patterns of light change as other waveforms interact with them(like in a puddle when it rains, or a bathtub) and therefore change colour, and a "visible shadow" must, in an image, have a contrast with light much brighter then eminating from the "shadow" area, leads me to believe there's a high probability of those wave patterns merging with the stronger patterns would only leave strongly contrasting patterns like complementary colors. Imho, yes complementary colors show up in "shadow" areas, but the "shadow" would have to be eminating light in the first place. But they always do technically speaking.
(there, there... just read it twice...hah hah, I hope I got it all right)
Existence of parallel universes hasn't been proven though, just FYI. He just demonstrated another oddity of light, which I thought was rather fun.

[jeremybirn]

TOn a Kelvin scale, light color shifts as the intensity increases or decreases.
Color temperature corresponds to the hue of a light, but doesn't really tell you about the intensity: those are independent. Sometimes a light gets bright enough to make an area appear to lose saturation, but that still isn't a color temperature shift.

-jeremy

PS - Agree with all others above - the CG option "shadow color" is a poor substitute for colored fill, bounce, and environment lights to tint the areas the key doesn't hit. Most painters consider the un-lit side of an object a part of the shadow, and add environmental colors and tones to the entire area un-lit by the main light source, not just to the area that is technically a cast shadow in CG terms. (If an object is opaque, it should cast a pure black shadow when it blocks a light; the colored illumination in the shadow area should come from other lights.)

[ZeroNeuro]

Talk about a blast from the past! haha

I wrote that post over 2 years ago and have since then learned a lot about lighting.

While I was speaking in terms of perception and Leonardo's theories, I do agree taht a shadow color is not to be tweaked too much.

Wow this post brings back memories!

And as far as using GI skylights and hdri domes... EWWW! ;) Why on earth would someone lose that much control?

I usually light traditionally and add an occlusion pass to the composite.

[jmBoekestein]

I really have to disagree!

What I'm going to do for my animations is model and texture a scene completely and extensively, render a couple of backdrops from that to rpf. And render a couple of HDRI's from Brazil to either OpenEXR or HDR format and use those to render out main characters and little grass things and so on in Maya mental ray. I doubt I'll ever loose control, well...maybe I have allready...:D...But I think I might have a look at the occlusion shader I recently downloaded, if it's faster I might try combining the two methods. Anyway, I'm going on theory here, 'cause I lack the experience.
2 years 'ey, I was just following links around. I bet this site is veritable goldmine if one digs deep enough!

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