POV-Ray : Newsgroups : povray.binaries.animations : Snap! [~600KB] Server Time
8 Jul 2024 08:31:35 EDT (-0400)
  Snap! [~600KB] (Message 1 to 2 of 2)  
From: Andrew the Orchid
Subject: Snap! [~600KB]
Date: 13 Nov 2004 06:30:46
Message: <4195f066@news.povray.org>
Um... yeah, that probably shouldn't happen...


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Download 'knots10-a-post.m1v.mpg' (575 KB)

From: Andrew the Orchid
Subject: Re: Snap! [~600KB]
Date: 13 Nov 2004 07:46:14
Message: <41960216$1@news.povray.org>
In order to avoid self-intersecting knots, the program performs an 
intersection test at each stage of the computation.

Specifically:
   * Each bead is processed in turn.
   * The resultant force on that bead is computed.
   * The new position of that bead is computed.
   * A triangle is constructed, having 3 corners:
     * New bead position.
     * Old bead position.
     * Next bead along.
   * Then every stick on the entire knot is tested to see if it 
intersects this triangle. If a single stick does intersect, the bead is 
left in its original position. (This applies only to that single bead.)

Stupid bug #3:
When performing the intersection tests, the stick endpoints are all 
identical [resulting in 0-length sticks]. Hence, *all* intersection 
tests pass, even when they shouldn't.

Duh.


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