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In lugnet.cad.dat.parts, Niels Karsdorp wrote:
> In lugnet.cad.dat.parts, Lars C. Hassing wrote:
> > In lugnet.cad.dat.parts, Steve Bliss wrote:
> > > I'm pretty sure that's going to be the problem with *any* partition
> > > of this surface into polygons. Having a mathematical description
> > > of the surface would be good, because then we could potentially
> > > create a primitive for the surface, and rendering programs could
> > > substitute a smooth-curve construct for the primitive.
> >
> > I have made a 43720.inc for the test of the coming L3PPARTS.
> > The mathematical description of the surface is:
> > 80x + 40y + yz = 0
> > and I have used the POV primitive quadric:
> > quadric {
> > <0,0,0>, <0,0,1>, <80,40,0>, 0
> > clipped_by { box { <-20,0,-40>, <0,20,40> } }
> > }
>
> Looks good.
> Should we create a new primitive with the next dimensions:?
> 2 24 0 0 1 0 1 1
> 2 24 1 0 -1 0 1 -1
> 2 24 0 0 1 1 0 -1
> 2 24 0 1 1 0 1 -1
> and a POV-quadric version in the coming L3PPARTS.
>
> As the outer twisted surface of the parts with this shape are
> pretty the same size, the inner surface differs among these parts
> (in 43720/43721 the inner surface has a z-size of 72,
> in 45407 the inner suface has a z-size of 76).
> With a general primitive it can be stretched to any dimension.
Nice, I like the idea of the quadric primitive, but we want to
add some curvature to the LDRAW version, right? I fiddled a bit
with the part a few days ago, starting with the two triangles
outlined by your primitive. I didn't exactly finish, but I think
if you take this and make a surface that follows the green X and
also follows the red stripes, you end up with something pretty
decent where the optional lines work.
Don
0 Wedge 4 x 2 Sloped Left
0 Name: 43721.dat
0 Author: Donald Sutter
0 LDRAW_ORG Part UPDATE 2004-04
0 Unofficial hack for testing purposes.
0
1 16 -10 0 30 0 0 1 0 1 0 -1 0 0 stud.dat
1 16 -10 0 10 0 0 1 0 1 0 -1 0 0 stud.dat
1 16 -10 0 -10 0 0 1 0 1 0 -1 0 0 stud.dat
1 16 -10 0 -30 0 0 1 0 1 0 -1 0 0 stud.dat
0
2 4 5 20 -20 0 0 -20
2 4 10 20 0 0 0 0
2 4 15 20 20 0 0 20
0
2 2 0 20 -40 3.75 15 -20
2 2 3.75 15 -20 5 10 0
2 2 5 10 0 3.75 5 20
2 2 3.75 5 20 0 0 40
0
2 2 0 0 -40 1.25 5 -20
2 2 1.25 5 -20 5 10 0
2 2 5 10 0 11.25 15 20
2 2 11.25 15 20 20 20 40
0
3 46 0 0 -40 0 20 -40 3.75 15 -20
3 46 0 0 -40 3.75 15 -20 5 10 0
3 46 0 0 -40 5 10 0 3.75 5 20
3 46 0 0 -40 3.75 5 20 0 0 40
0
3 45 20 20 40 0 20 -40 3.75 15 -20
3 45 20 20 40 3.75 15 -20 5 10 0
3 45 20 20 40 5 10 0 3.75 5 20
3 45 20 20 40 3.75 5 20 0 0 40
0
1 16 0 0 0 -1 0 0 0 1 0 0 0 1 s\43720s01.dat
0
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In lugnet.cad.dat.parts, Don Heyse wrote:
> Nice, I like the idea of the quadric primitive, but we want to
> add some curvature to the LDRAW version, right? I fiddled a bit
> with the part a few days ago, starting with the two triangles
> outlined by your primitive. I didn't exactly finish, but I think
> if you take this and make a surface that follows the green X and
> also follows the red stripes, you end up with something pretty
> decent where the optional lines work.
>
> Don
>
>
>
>
> 0 Wedge 4 x 2 Sloped Left
> 0 Name: 43721.dat
> 0 Author: Donald Sutter
> 0 LDRAW_ORG Part UPDATE 2004-04
> 0 Unofficial hack for testing purposes.
> 0
> 1 16 -10 0 30 0 0 1 0 1 0 -1 0 0 stud.dat
> 1 16 -10 0 10 0 0 1 0 1 0 -1 0 0 stud.dat
> 1 16 -10 0 -10 0 0 1 0 1 0 -1 0 0 stud.dat
> 1 16 -10 0 -30 0 0 1 0 1 0 -1 0 0 stud.dat
> 0
> 2 4 5 20 -20 0 0 -20
> 2 4 10 20 0 0 0 0
> 2 4 15 20 20 0 0 20
> 0
> 2 2 0 20 -40 3.75 15 -20
> 2 2 3.75 15 -20 5 10 0
> 2 2 5 10 0 3.75 5 20
> 2 2 3.75 5 20 0 0 40
> 0
> 2 2 0 0 -40 1.25 5 -20
> 2 2 1.25 5 -20 5 10 0
> 2 2 5 10 0 11.25 15 20
> 2 2 11.25 15 20 20 20 40
> 0
> 3 46 0 0 -40 0 20 -40 3.75 15 -20
> 3 46 0 0 -40 3.75 15 -20 5 10 0
> 3 46 0 0 -40 5 10 0 3.75 5 20
> 3 46 0 0 -40 3.75 5 20 0 0 40
> 0
> 3 45 20 20 40 0 20 -40 3.75 15 -20
> 3 45 20 20 40 3.75 15 -20 5 10 0
> 3 45 20 20 40 5 10 0 3.75 5 20
> 3 45 20 20 40 3.75 5 20 0 0 40
> 0
> 1 16 0 0 0 -1 0 0 0 1 0 0 0 1 s\43720s01.dat
> 0
The following are the appropriate conditionals for Don's surface. Playing with
it you can have angles where the conditionals seem to go too far, but it's
certainly much better than the current ones.
(Note that the last 4 conditionals are only there to keep the surface smooth in
LDView. I'm not sure if that's appropriate or not, but it looks a whole lot
better in LDView with them present. It looks positively wretched without
them.)
0
5 24 0 0 -40 3.75 15 -20 0 20 -40 5 10 0
5 24 0 0 -40 5 10 0 3.75 15 -20 3.75 5 20
5 24 0 0 -40 3.75 5 20 5 10 0 0 0 40
0
5 24 20 20 40 3.75 15 -20 0 20 -40 5 10 0
5 24 20 20 40 5 10 0 3.75 15 -20 3.75 5 20
5 24 20 20 40 3.75 5 20 5 10 0 0 0 40
0
5 24 0 20 -40 3.75 15 -20 0 0 -40 20 20 40
5 24 3.75 15 -20 5 10 0 0 0 -40 20 20 40
5 24 5 10 0 3.75 5 20 0 0 -40 20 20 40
5 24 3.75 5 20 0 0 40 0 0 -40 20 20 40
0
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In lugnet.cad.dat.parts, Travis Cobbs wrote:
> In lugnet.cad.dat.parts, Don Heyse wrote:
> > Nice, I like the idea of the quadric primitive, but we want to
> > add some curvature to the LDRAW version, right? I fiddled a bit
> > with the part a few days ago, starting with the two triangles
> > outlined by your primitive. I didn't exactly finish, but I think
> > if you take this and make a surface that follows the green X and
> > also follows the red stripes, you end up with something pretty
> > decent where the optional lines work.
>
> The following are the appropriate conditionals for Don's surface.
> Playing with it you can have angles where the conditionals seem to
> go too far, but it's certainly much better than the current ones.
Hey, thanks testing it out. You're right about the conditionals
zig-zagging a bit. I still have the feeling that if the surface
were pinned down to the concave green line those zig-zags would
go away. But I couldn't decide whether to divvy it up with cuts
sorta parallel to the convex green line (like the torus primitives)
or with another fan outta one (or two) of the other corners. I
was kinda hoping that maybe with your superior math intuition, you'd
just know the right answer... ;^)
> (Note that the last 4 conditionals are only there to keep the surface
> smooth in LDView. I'm not sure if that's appropriate or not, but it
> looks a whole lot better in LDView with them present. It looks
> positively wretched without them.)
I'd keep 'em for now. But maybe this weekend I'll try and scale it
down to the 1x1x1 primitive size and pin the surfaces down to that
concave curve. Then it'll need a whole new set of conditionals.
Don
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