Subject:
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Re: Why Type 5 Lines?
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Newsgroups:
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lugnet.cad.dev
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Date:
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Wed, 17 Apr 2002 18:38:09 GMT
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Viewed:
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390 times
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Fredrik Glöckner wrote:
> "Orion" <pobursky@hotmail.com> writes:
>
>
>
> On the contrary, I think that type-5 lines are very useful, and an
> interesting solution. They are a nice way to make sure that rounded
> objects are outlined with a contrasting colour, no matter where the
> viewpoint is. The rendering of cylinders and spheres is greatly
> enhanced byt type-5 lines, I think. You can try yourself to view
> objects with or without type-5 lines in L3Lab. Use the menu under
> "View".
I believe that there are other ways to put these lines in, as long
as you are *only* planning on using them to show the 'visible' edge
of a curved surface. This is actually a question I've been meaning
to ask around here, Have type5 lines been used in 'other' ways in
the Ldraw library? I don't know what other special effects you could
achieve, but it wouldn't surprise me if there were some? Does anyone
know?
>
> By the way, is the "type-5" solution a common one in the CAD world, or
> was it sort of invented by Jessiman? I don't know enough about CAD to
> answer this myself.
>
I don't know if something similiar might ahve been used early on,
but I don't remember seeing anything like it lately. This may be because
OpenGL and other libraries have other ways of achieving the same effect.
In order to get OpenGL to do this for you though you need to have the
polygons that represent the curved surface tied together in a 'strip'.
If you can do that, then you can have OpenGL render them once a solid
faces, and again as a wireframe. In my experience, when OpenGL renders
strips and fans as wireframes, it will only draw the edges required to
show where the curved surface disappears from view.
This is the main reason why I'm trying to automate 'stripifying' the
LDraw polygons. The Rendering Library I use has no way for me to tell
it wether to draw a line or not at final render time. It would be pretty
hard for me to even go through ahead of time an figure out each type5
line based on the view point, but that maybe possible. Instead though,
I'm putting my trust in this 'feature' of how strips and fans are drawn
so that I can get the same (or close) drawings, and just ignore the
type5 lines during loading.
Of course if they've been used for other things as I asked above then
I may have to make other arangements - Or just live with the differences
in the output. :(
-Kyle
--
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-------------------------------ooO( )Ooo-------------------------------
Kyle J. McDonald (o o)
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\\\//
(o o) kmcdonald@BigFoot.COM
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Message has 1 Reply:
 | | Re: Why Type 5 Lines?
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| (...) Tell more about this. I just tweaked a version of ldview to display type 5 lines, but only for surfaces that haven't been replaced by quad strips. It looks good with primitive substitution turned off, but with this automagic wireframing of (...) (23 years ago, 17-Apr-02, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Why Type 5 Lines?
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| (...) On the contrary, I think that type-5 lines are very useful, and an interesting solution. They are a nice way to make sure that rounded objects are outlined with a contrasting colour, no matter where the viewpoint is. The rendering of cylinders (...) (23 years ago, 17-Apr-02, to lugnet.cad.dev)
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