AuthorTopic: Pixel school  (Read 45212 times)

Offline Helm

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Re: Pixel school

Reply #60 on: August 07, 2005, 06:52:11 pm
Thanks for the info. So then, following the example above, what would happen if you hit a mostly yellow object (thinking of the banana still) with a somewhat blue light (I say something, let's forget pures for a moment). What colour will the banana be, and what colour will the shadow be?

Offline crab2selout.png

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Re: Pixel school

Reply #61 on: August 07, 2005, 07:51:38 pm
http://www.itchstudios.com/psg/art_tut.htm
So I think I'm beginning to understand this subsurface scattering thing. Light passes under something, bounces around and comes out. Because it has to be able to penetrate, an object like say solid steel, can't have subsurface scattering. One thing I'm not clear enough on, is does the light always make it out of an object? For there to actually be a glowing effect light has to get stuck under the surface right? Or does light have a cumulative effect, where simply hitting a surface temporarily lightens it, even if the light bounces off?


@trick: so based on your example, does that mean that any warm colour can reflect all warm colours, and any cool colour can reflect all cool colours? Like R reflects, R, Y, and O? When I was explained colour spectrum, green was like an in between colour, so does it get to reflect warm and cool colours, or just green?

Offline AlexHW

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Re: Pixel school

Reply #62 on: August 07, 2005, 08:34:54 pm
Crab, I think its best to think of the amount of light which hits your eye from a specific location. Whether light can get stopped/stuck under something, im unsure.. But to see the glowing effect, light has to penetrate the skin, bounce around and pass through the blood which in effect causes the light's wavelengths or whatever to change and then the light has to exit the skin and enter your eye for you to see the effect.. The more light doing this in the specific location, the more intense it would be i think..

mm.. as for what color surfaces reflect other colors, think of it like this..
A surface will either absorb or reflect light. A yellow object looks yellow because it has absorbed any wavelengths which are not yellow and reflected only the yellow, and this yellow wavelength then enters your eye and you see yellow..
In the case of the blood under the skin, the light would penetrate under the skin and wavelengths which are not red which hit the blood, would get absorbed and the red wavelengths would be reflected and these would bounce back out of the skin and into your eye therefor you see red there..
If a light didnt have a certain wavelength such as red, then if that light penetrated the skin and hit the blood, all the wavelengths would be absorbed and nothing would be reflected, and so no wavelengths could then come back and enter your eye from that location and so you would see black there..

Offline Mercury Rising

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Re: Pixel school

Reply #63 on: August 07, 2005, 10:41:04 pm
Hmm, I missed the first day of school, soz wasnt home. Im enrolling though.  Atm im drawing my alien piece.
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Offline lief

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Re: Pixel school

Reply #64 on: August 07, 2005, 10:43:11 pm
schools in!  thanks for the input and comments people, great to see.

clarify a few things:

1.  The shadow APPEARS to be opposite colour.  This is a optical delusion, the same as placing a light color in the middle of dark area will make it (the light color) look brighter.  Helm was spot on with this one.
2. 
Quote
trick: Sorry, but that's pretty much wrong, actually.  For example, if a pure yellow object (meaning no "blue wavelengths") gets hit by pure blue light (only blue wavelengths) and nothing else, the object will appear black.

In theory this is correct.  In actual practice, it would be very rare to get such purity of waveform.  For this to work it would  have to be nearly laboratory conditions eg.  Blue light at EXACT wavelength of the blue that is being absorbed in the banana surface, most likely with filters to bandpass this accurately, with absolutely no ambient light.

As was mentioned by Helm, subtlety is the key.  Tint light gently, not by huge amounts that are going to make bananas black.  Anything that you shine on a banana that makes it black can't be that good can it?

4.  Ptoing is correct on the desaturated / saturated shadows, this is sometimes what people refer to as 'warm' shadows.  On a quick side note, borrowed from traditional art, a good way to make human skin look real is to add some highlights of very very transparent red, eg on the cheeks and nose.  This would be a general simulation of some subsurface effects and the blood affecting the perceived color of the skin above it.   This of course wouldn't apply as much to sick or cold people :)

4. The best way to prove/disprove/investigate all this is WITH YOUR OWN EYEBALLS.  Look around, wake up, pay attention.  Get some colored cellophane and a torch and check it out...

Now to my students:

Tiktak: Of course it isn't.  I'll pm you with some details.
NG:  Very good.  We are lacking some contrast between the UFO and the rest of the picture though.  It needs to be darker I tell you! :)
Bel:  Nice job.  Should do the tips of the tentacles waving around too, it will sell the idea that they are tentacles.  Don't explode the guy so much where he is ripped, have skin connecting in strands, same with intestines and ligaments.  I'll do an edit if you like.
Get rid of the outlining soon.  We also need to add a small shadow to let the viewers know how high from the ground he is.  You can also make the ground darker to get this effect.
BroInWar: Thats fine, just review the thread.  Its big, so set aside some time.  good luck with your lineart.

big welcome to tiktak and brotherinwar, good luck with pixelling!

Offline Mercury Rising

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Re: Pixel school

Reply #65 on: August 07, 2005, 10:56:21 pm
OK I should have just waited to post but I wanted to enroll.  Honestly I dont know what it is, somehow its an alien.  Just wanted to post the lineart cus so many poeple are on right now.  Its a, um, er, floating alien in robes with a helmet on.  Yeah...
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Offline Negative Gravity

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Re: Pixel school

Reply #66 on: August 07, 2005, 10:57:49 pm
Ok... lief, you wanted dark.. here is dark!  :D



I'm not sure I think I downed the luminosity by like 100 on the lightest shade of gray.

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Offline crab2selout.png

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Re: Pixel school

Reply #67 on: August 07, 2005, 11:19:43 pm
Oh man, I think I suffered an epiphany. Shit, that makes so much sense, Alex, thank you! Alright, so a banana and an apple at nght would be black or near black since they would absorb the blue light and it would therefore not hit our eyes. And now for some examples to see if I learned as much as I think I did.

http://www.ziggum.com/images/Nissan/P5221431.JPG
A banana at night would look a lot like the steering wheel in this picture. Everyhing in this picture looks black bescause it absorbs the blue light that is created. Anything that can reflect blue light(like purple) however, will show up as blue regardless of it's original colour, because the only light being reflected is blue, and nothing else. Also, judging by the lack of anything that looks red, there is nothing that is either orange or red in the cab.

http://rclsgi.eng.ohio-state.edu/~bhandari/chicagosnaps/Nighttime%20chicago.JPG
And for another example, the foreground in this picture is orangey yellow because that's the colour it reflects from the lamp post. I can tell the most of the buildings in the distance are neither orange, red or yellow because if they were then they would've reflected nearby light at the camera. The buildings that are orange near the right, and near the left are likely orange, yellow or red because they are reflecting light.

Mabye there's couple problems there since light isn't always pure, but I thik I get how it would be in ideal conditions.

And I think I get the subsurface scattering thing more too, The reason that subsurface scattering gives a glowing effect and is more saturated is because there's more light hitting the eye. This extra light being the light reflected from layers below the skin in addition to the light reflected off the surface of the skin

Damn, now I can't wait until it gets dark in a couple hours. I'm gonna walk around and check out the shadows and junk. Of course, before I do that I would have to short circuit the city's power supply or something and knock out all the damn street lights. Well, I'll get a little practice at least by seeing how the for the most part I'll jsut be seeing blue and yellow-orange stuff. I guess I might have to plan a visit to the country or something.

Anyhow, thank you Trick, Helm and Alex, I get the feeling that this thread is going to become a big source of the material for the wiki.

Offline AlexHW

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Re: Pixel school

Reply #68 on: August 07, 2005, 11:54:45 pm
mm.. yeah i think you may be beginning to understand, kinda hard for me to follow what you said though :P

Those lights in the first pic may not be bright enough to illuminate the whole car and perhaps that is why alot of the car is black..
but, it could also be that the surfaces inside the car which are seen as black are because they can't reflect any certain wavelength in the light back into your eye from the location of the surface, so they instead absorb it (or don't reflect/absorb anything because there is no light there to do that).

The second pic has artificial lights which look kinda yellowish/orange, and so they most likely are emitting light which has stronger wavelengths of this yellowish/orange, or the other wavelengths are dimmer than the yellowish/orange wavelengths, and so you get this tinted light.. now.. when this light hits say, the surfaces near it, the dimmer wavelengths won't be pronounced enough to be seen even if they get reflected into your eye if this yellowish orange is also reflected.. and so the surfaces get tinted.. but keep in mind that this required all wavelengths to be reflected.. (can see this in the concrete/stone surfaces which are grey-ish/white which reflects any color) (the buildings are also probably a desaturated white and so they also reflect all the wavelengths in the light..)

now.. say there is a surface which absorbs the yellow/orange and reflects the rest of the dimmer wavelengths, what you see then is the surface very dark, but it may be a very dim green or blue and such (for example the grass or plants)..

someone correct me if im wrong..
« Last Edit: August 07, 2005, 11:56:26 pm by Alex Hanson-White »

Offline Negative Gravity

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Re: Pixel school

Reply #69 on: August 08, 2005, 12:05:15 am
Dang... this isn't school, it's like collage  :o lol.
I think this is going to need it's own topic pretty soon.

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