Subject:
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Re: Stud5 and type 5 lines at edge of cylinders.
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Newsgroups:
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lugnet.cad.dat.parts.primitives
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Date:
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Sun, 17 Aug 2003 19:26:35 GMT
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Viewed:
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3594 times
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In lugnet.cad.dat.parts.primitives, Travis Cobbs wrote:
> In lugnet.cad.dat.parts.primitives, Don Heyse wrote:
> > In lugnet.cad.dat.parts.primitives, Mark Kennedy wrote:
> > > I recently reworked the stud 5 primitive to make use of more quarter
> > > cylinders. I then noticed that when viewed there were edge lines
> > > apearing where they shouldn't. If you look at the primitive from
> > > various points you can see this occur.
> >
> > Ahh, the dreaded S-curve cylinder join rears it's ugly head again.
> > I voted to ignore this a while back and gave my reasons.
> >
> > http://news.lugnet.com/cad/dev/?n=7192
> >
> > Nobody disagreed at the time.
>
> Is there a reason that the cylinder primitives haven't been updated to work like
> the sphere primitive? As long as there are type 5 lines on both ends of each
> partial cylinder, and the control point out in space is tangent to the cylinder
> instead of being at the next point on the cylinder approximation, the problem
> goes away.
I don't think the S curve problem goes away. The tangent control point
works perfectly for two (same radius) curves that both curl in the same
direction. It also works perfectly for a curve joining a flat edge
along the tangent.
However it only reduces the problem (by half) for two curves joined
in an S shape. However with your fix, the problem also approches
0 as the number of segments in the curve approaches infinity. I think
it's good enough for low res curves when used for tiny geometry like
studs, and good enough with the higher resolution curves for larger
bits.
So if the primitives haven't been updated with the tangent control
points at the ends, they should be.
Any volunteers?
> . My vote
And mine.
> would be to update the partial cylinder primitives. Note that the partial
> sphere primitive is already coded in this way; I'm not sure why the partial
> cylinder primitives aren't.
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