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 CAD / Development / 10024
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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 00:10:51 GMT
Viewed: 
1561 times
  
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. Does the -dist option affect this test too, or just the coplanar quad
test? Maybe there could be another option in l3p to adjust the accuracy of the
colinearity test? Or is there one already and I missed it?

ROSCO



Message has 2 Replies:
  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 (...) (20 years ago, 8-Jan-05, to lugnet.cad.dev)
  RE: *** SPAM *** Re: Very small triangle and a quad that thinks its a tri
 
(...) Only at 5dp (ie -det/-dist of 0.00001), but then as the values are only to 5dp this is not surprising! The co-linear vertices are reported for any -det/dist values from 1 to 0.00001 William (20 years ago, 8-Jan-05, to lugnet.cad.dev)

Message is in Reply To:
  Very small triangle and a quad that thinks its a tri
 
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 (...) (20 years ago, 7-Jan-05, to lugnet.cad.dev)

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