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 CAD / Ray-Tracing / 2139
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Subject: 
Re: "Illusions"
Newsgroups: 
lugnet.cad.ray
Date: 
Wed, 3 Mar 2004 18:57:12 GMT
Viewed: 
2183 times
  
In lugnet.cad.ray, Mike Thorn wrote:
   But looking at the results it just confuses me more. What do you think? Are these the colors that should occur according to your theory?

Not exactly, but pretty close. The 100 looks like it might be about right, but the 010 is more purple than magenta, and the 001 is clearly yellow and not amber (the nofilter flames look closer to amber). It’s almost as if you’re programming the reflected color of the flame and that determines the inverted color of the shadow. Maybe trying 110, 101, and 011 would produce the specific results that I expected, but regardless the experiment confirms that the flame color changes in relation to the flame image color. 111 looks really funky, with the black flames casting bright white shadows. Anyways, I was thinking about this, and I’m wondering if it’s possible to program the flames actual light sources, or if that would require putting lots of little light sources inside of them.

Looking back at your documentation, the Filter setting should be the rough equivalent of shining light through a piece of colored glass, while the Transmit value should be the rough equivalent of shining light through the holes in a stretched piece of cloth. Filtered light should remove (not reflect) light that contrasts with the color of the object (magenta or amber light shining through a cyan filter will appear blue and green, respectively, because those are the colors that cyan will allow through, while the red light in both should be absorbed). Transmitted light should just reduce in intensity, regardless of the color of the object it shines through.

Again, I’ve never done any CGI work before, so I can’t tell you exactly why your flames are reflecting one color while allowing an opposing color to pass through (and I certainly can’t tell you how to correct it), but there’s clearly a value that’s not set properly in there somewhere. I have a friend who did CGI work in college, and his stained glass windows would cast matching shadows on the floor, so I know it’s possible to get an object to filter out light that contrasts with the color of the object instead of light that matches it.



Message is in Reply To:
  Re: "Illusions"
 
(...) Well, let me try it. I tried RGB values for the flames of 1,0,0 - 0,1,0 - 0,0,1 1,1,1 - 0,0,0 respectively. (URL) Deeps (each image under 12K): (5 URLs) But looking at the results it just confuses me more. What do you think? Are these the (...) (21 years ago, 3-Mar-04, to lugnet.cad.ray, FTX)

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