Subject:
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Parts as volumes (instead of surfaces)
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Newsgroups:
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lugnet.cad.dev.org.ldraw
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Date:
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Sat, 6 Apr 2002 22:20:31 GMT
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Viewed:
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245 times
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It has been said that, with ldraw parts, we have the geometry of TLG bricks.
This is rather optimistic. Because geometry would be CSG descriptions that
allow much more (although slower) than quads and triangles. CSG descriptions
allow part collision detection.
Thinking about BFC statements I realised they also allow collision detection.
The prerequisite is having convex parts. Each polygon defines a tangent
plane, an "exterior" half-space and an "interior" half-space. A part is
defined by the intersection of these interior halve-spaces that are
organized in a BSP tree. I guess collision detection is then a standard
procedure on BSP trees. Or may be I am wrong and this is actually a much
more complex problem.
Anyway, the remaining problem is that most (if not all, including Brick 2 x
4) ldraw parts are not convex but concave. Is there any simply mean to
extend BFC with metacommands that split ldraw parts in convex subpart? Does
the topic deserve the effort? Any interest at all? Just an idea to see what
reply.
Damien
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Message has 3 Replies:
 | | Re: Parts as volumes (instead of surfaces)
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| (...) Wow, good questions. We know that some collision detection is already practical - Eric Olsen demonstrated that over a year ago. But decomposing LDraw parts into convex objects, that would be a trick. Each external box 5 (or pair of box 5's) (...) (22 years ago, 8-Apr-02, to lugnet.cad.dev.org.ldraw)
| | | Re: Parts as volumes (instead of surfaces)
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| If you're interested, take a look at my old Rayshade libraries that made the bricks from scratch using CSG. I'm especially fond of the L3G0 40-tooth technic gear. I've thought it would be nice to have "bounding boxes" for the bricks, for collision (...) (22 years ago, 9-Apr-02, to lugnet.cad.dev.org.ldraw)
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