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 CAD / Development / 10027
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Subject: 
Re: Very small triangle and a quad that thinks its a tri
Newsgroups: 
lugnet.cad.dev
Date: 
Sat, 8 Jan 2005 09:55:56 GMT
Viewed: 
4543 times
  
In lugnet.cad.dev, Lars C. Hassing wrote:
> In lugnet.cad.dev, Ross Crawford wrote:
> > In lugnet.cad.dev, William Howard wrote:
> > > Whilst working out the non-right-angled cylinder intersection sub-parts for the
> > > Boat Rigging pieces I have run into two related problems
> > > 
> > > 1) I have a triangle A-B-C that is so tiny that L3P reports it as co-linear and
> > > L3Lab doesn't render it (it looks OK in MLCad though)
> > > 2) I have a large quad C-B-D-E that L3P reports B-C-E as co-linear and L3Lab
> > > doesn't render (but again looks OK in MLCad)
> > > 
> > > Now the triangle and the quad share the very short edge B-C but are not
> > > co-planar so I can't replace them by any larger combinations.  Also, omitting
> > > A-B-C and making the quad into a tri leaves obvious gaps as the sub-part is
> > > scaled when it is used.
> > > 
> > > Should I
> > > a) ignore these "errors" as they arn't really errors and assume that other
> > > renders will render them OK (like MLCad does)
> > > b) pre-scale the sub-part (which seems counter-intuitative as it then doesn't
> > > follow the pattern of the right-angled cylinder intersection sub-parts)
> > 
> > I'm guessing this is a limitation of the accuracy of the l3p -check, so probably
> > ignorable.
> 
> I think so too.
> William, could you please e-mail me the actual coordinates of A, B, etc.,
> and perhaps the whole file.
I'll send you the whole file (its not complete yet), but the values for the tri
are
  A (0.989107, -1, 0)
  B (0.997785, -0.98677, 0.06652)
  C (0.997785, -1, 0.06652)

William



Message has 1 Reply:
  Re: Very small triangle and a quad that thinks its a tri
 
(...) That's a small triangle! Side lengths: 0.0684 0.0671 0.0132 The reason it doesn't show in L3Lab is that you have color coded it in your file! Back in 1998 PovRay would crash if it was given a triangle with collinear vertices and a texture (...) (22 years ago, 14-Jan-05, to lugnet.cad.dev)

Message is in Reply To:
  Re: Very small triangle and a quad that thinks its a tri
 
(...) I think so too. William, could you please e-mail me the actual coordinates of A, B, etc., and perhaps the whole file. (...) Good question! (...) The colinearity test currently has a hardcoded threshold of 0.01. The colinearity test is carried (...) (22 years ago, 8-Jan-05, to lugnet.cad.dev)

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