Subject:
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Re: Help needed with cond. lines
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Newsgroups:
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lugnet.cad.dat.parts
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Date:
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Thu, 3 Apr 2003 05:36:20 GMT
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Viewed:
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1177 times
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I've created another drawing to help illustrate my descriptions below.
Please refer to it while reading below. You can find it here:
http://www.halibut.com/~tcobbs/pics/helmet-fix2.gif
In lugnet.cad.dat.parts, Willy Tschager writes:
> 0
> 0 the edge between the two primitives is: 14.5 4 0 14.5 7 0
> 0 why do you put the first two vertexes at Y=7 and Y=17?
> 0
> 0 Travis Cobbs - fixed:
> 5 24 14.5 7 0 14.5 17 0 14.219 4 1.416 14.219 7 -1.416
> 0
The edge between the two ndis primitives is empty space. Conditional lines
should never be put in empty space. In fact, you will see it pop into
existence if you rotate around to just the right angle. Due to the angles
involved, this is hard to see, but it does happen. This line goes from 4 to
7 in the y axis, and shouldn't be there at all. I simply moved it down to
the range of 7 to 17 in the Y axis (see below for why).
> 0 also this looks wired to me. could you give me a more
> 0 detailed explanation. is it due to the two primitives?
> 0 why is the first vertex at Y=17 and not 4 or 7?
> 0
> 0 Travis Cobbs - fixed:
> 5 24 14.5 17 0 14.5 21 0 13.396 4 5.549 13.396 21 -5.549
> 0
The original line went from 7 to 21 in the Y axis. From the standpoint of
the original design of conditional lines, there was absolutely nothing wrong
with it, and it would work great highlighting the silhouette.
However, my curve smoothing code only works when the conditional lines
exactly match the edges of the shapes that need smoothing. Since there are
two triangles on the right of this conditional line and two quads on the
left, the smoothing doesn't happen. There has to be exactly one polygon on
each side, with two points in common with the conditional line end points
for any smoothing to occur.
What I did was split the one conditional line into two conditional lines.
Since you had another conditional line that wasn't supposed to be there (the
one between the two ndis primitives), I simply changed that one to handle
the top portion, and changed the long one to just handle the bottom section.
> to sum up: it looks like I still lack a proper understanding of cond. lines
> :-((( this could also be the reason why I'm in deep trouble with an other
> area of the helmet, involving another primitive and a "flouting" edge. have
> a look at the code:
<code removed>
>
> initially I used a quad between the cylinder and the beginning of the visor
> hole, than I splitted it off into triangles, but still both edges aren't
> round. what's wrong? I really would appriciate your helping hand.
There's nothing really wrong with what you have. The problems you are
seeing are caused by two different things. If you turn primitive
substitution off in LDView, you will see that the join between the
half-cylinder and the other geometry becomes smooth. Unfortunately, my
curve smoothing doesn't smooth across the boundary between a substituted
primitive and regular geometry. I don't think I'm going to be able to fix
this any time soon, either.
I think that the other problem you are referring to is the join between the
regions shaped like the ndis primitive and the polygons behind them. If you
zoom in far enough, you will see that these are actually being smoothed.
The problem is that the edge triangles in the ndis-shaped areas are too
narrow to provide good looking smoothing.
You could probably decrease the effect by moving points around, but I'm not
sure it is worth the effort, and I think it would require some
experimentation. I have posted a possible alternative that MIGHT look
better in the following location:
http://www.halibut.com/~tcobbs/pics/helmet-fix3.gif
I hope this at least clears up your confusion, even if it doesn't actually
solve the problem.
--Travis Cobbs (tcobbs@REMOVE.halibut.com)
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Message has 1 Reply:
Message is in Reply To:
 | | Re: Help needed with cond. lines [DAT]
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| (...) hi travis, thx for your suggestion. the removed lines are clear to me. I added them in a desperate attempt to smooth the primitive - just to see if I could rid of the problem, but I do NOT understand the fix. I added my comments below: 0 (...) (22 years ago, 2-Apr-03, to lugnet.cad.dat.parts)
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