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 CAD / LDraw Files / Parts / 5654
5653  |  5655
Subject: 
Re: Conditional lines on sloped wedge parts 43720 and 43721
Newsgroups: 
lugnet.cad.dat.parts
Date: 
Mon, 18 Apr 2005 14:02:53 GMT
Viewed: 
4381 times
  
In lugnet.cad.dat.parts, Steve Bliss wrote:
   In lugnet.cad.dat.parts, Niels Karsdorp wrote:
   Wedge part 45407 (Wedge 4 x 4 with 1 x 4 Side Plates) has similar sloped sides as wedge parts 43720 and 43721 . When I examined these parts in LDView, I noticed that the control points for the conditional lines on the sloped surface might be wrong:


I don’t think it’s the control points. I took a quick look at the file, actually just one of the lines, the first in the file. The control points used are the two unattached vertices from the triangles adjacent to the conditional edge. That should be exactly right.

It might be more the way the sloped surface is designed. These two images show how the conditional lines are sometimes “half-needed”:



I suspect that LDraw cannot outline this surface exactly correctly -- but I haven’t thought it through yet; I could be wrong.

A finer-grained surface, with more polygons, would work better. But would still have the problem of ‘half-needed’ conditional lines.

I’m not sure about that. The surface as it’s written is extremely lumpy, and the conditional lines work as expected given the lumps in the surface. You also get an ugly shading effect with flat shading because of those lumps.



There’s gotta be a way to cut the polys through the middle of the saddle and eliminate the problem. It looks like it might involve a ring (or torus) primative?

  
   Before I want to upload part 45407, I want to be sure how to create correct conditional lines for such sloped surfaces.

Yes, this should be cleared up.

Steve



Message has 1 Reply:
  Re: Conditional lines on sloped wedge parts 43720 and 43721
 
(...) Well, I thought about this, and what I would try is changing the polygons thus: If the top points are A1-5 and the bottom points are B1-5, keep the A2-B1, A3-B2 as currently, but instead of A2-B2 etc, use A3-B1, A4-B2, etc. I think that would (...) (19 years ago, 18-Apr-05, to lugnet.cad.dat.parts, FTX)

Message is in Reply To:
  Re: Conditional lines on sloped wedge parts 43720 and 43721
 
(...) I don't think it's the control points. I took a quick look at the file, actually just one of the lines, the first in the file. The control points used are the two unattached vertices from the triangles adjacent to the conditional edge. That (...) (19 years ago, 18-Apr-05, to lugnet.cad.dat.parts, FTX)

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