Subject:
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Re: Problem with Primitive Generator
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Newsgroups:
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lugnet.cad
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Date:
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Wed, 26 Sep 2007 16:47:07 GMT
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Viewed:
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2196 times
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In lugnet.cad, Philippe Hurbain wrote:
> ...actually the problem is not specific to PrimGen (btw, thanks Paul
> for this great tool!) but appears when some rounded primitive meet a
> straight surface: conditional lines at the edges of these primitives
> appear when they shouldn't.
>
> See http://www.brickshelf.com/gallery/Philo/Misc/primgenbug1.png. The
> right side shows a 1-4cone24 and the unwanted line, the left side is
> a 1-4cyli (official primitive) that behaves correctly.
>
> The origin of this issue is obvious here:
> http://www.brickshelf.com/gallery/Philo/Misc/primgenbug3.png, the
> control point of the cylinder matches the flat surface, while the
> cone control point matches the next section of a cone.
>
> Note that the problem is not specific to cones, it also happens with
> toruses (http://www.brickshelf.com/gallery/Philo/Misc/primgenbug2.png).
> A 1-4cyli created with PrimGen also shows this behavior.
I think a solution that mostly works was invented around this
time frame:
http://news.lugnet.com/cad/dat/parts/?n=3375
Instead of using cylinder primitives with an optional line at one end
that expects to be mated with a similar cylinder primitive, you use
optional lines at both ends that share the work by dividing the curve
angle in half. This puts the optional line control points on the
tangent plane, which allows you to mate a cylinder primitive with
another cylinder or with a quad in the tangent plane. But it doesn't
work for S curves made of two cylinder primitives mated in the
opposite direction.
I don't think this was ever implemented for cylinders, but it might
have made it into some of the sphere primitives. More info here,
with pictures and some discussion of the primitive generator.
http://news.lugnet.com/cad/dat/parts/primitives/?n=350&t=i&v=a
Don
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Message has 1 Reply:
 | | Re: Problem with Primitive Generator
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| (...) Yes, that's the way cylinder primitives are done, and it seems to work very well. I think other primitives could be improved that way. (...) That case is not that bad - the angle where the middle line appears is divided by two, so it is an (...) (17 years ago, 26-Sep-07, to lugnet.cad)
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Message is in Reply To:
| | Problem with Primitive Generator
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| ...actually the problem is not specific to PrimGen (btw, thanks Paul for this great tool!) but appears when some rounded primitive meet a straight surface: conditional lines at the edges of these primitives appear when they shouldn't. See (URL) The (...) (17 years ago, 26-Sep-07, to lugnet.cad)
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