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 CAD / Development / Macintosh / 1054
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Subject: 
Re: Bricksmith 2.4: Faster. Much Faster.
Newsgroups: 
lugnet.cad.dev.mac, lugnet.cad.dev
Followup-To: 
lugnet.cad.dev
Date: 
Wed, 16 Jun 2010 16:53:51 GMT
Viewed: 
35290 times
  
In lugnet.cad.dev.mac, Don Heyse wrote:
   In lugnet.cad.dev.mac, Don Heyse wrote:
   In lugnet.cad.dev.mac, Remi Gagne wrote:
   In lugnet.cad.dev.mac, Allen Smith wrote:
  
By the way, Bricksmith does not render conditional lines. I consider shading to be a sufficient substitute, and conditional lines sound difficult to optimize.

Heh, you hit that problem too? I’ve played around writing an OpenGL LDraw renderer based exclusively on display lists, but I can’t for the life of me figure out how to handle conditional lines in this setup. Has anyone else solved this peculiarly specific problem?

You can ignore the conditional lines and achieve the same effect with display lists using the stencil buffer techniques presented here:

http://www.opengl.org/resources/code/samples/sig99/advanced99/notes/node108.html

And here’s a silhouette technique using BFC:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.71.8503&rep=rep1&type=pdf

This technique and the conditional lines both target the same edges lines where the front facing polygons meet the back facing polygons, so the results should be quite similar.

And another thing...

The BFC technique actually has an advantage over conditional lines because it works on the entire scene after it’s been assembled. Whereas the conditional lines at the edges of the primitives are created in advance, and must predict what they’re going to butt up against when the entire scene has been assembled. This prediction may not always be right, resulting in missing conditional lines and some visible where they should not be.



Message has 1 Reply:
  Re: Bricksmith 2.4: Faster. Much Faster.
 
(...) So finally this brings us to a technique that combines the predictive abilities of the conditional lines with the runtime advantages of the stencil and BFC algorithms. Think of the conditional line as a pair of triangles with a shared edge (...) (14 years ago, 16-Jun-10, to lugnet.cad.dev, FTX)

Message is in Reply To:
  Re: Bricksmith 2.4: Faster. Much Faster.
 
(...) (URL) technique and the conditional lines both target the same edges lines where the front facing polygons meet the back facing polygons, so the results should be quite similar. (14 years ago, 16-Jun-10, to lugnet.cad.dev.mac, FTX)

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