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 CAD / LDraw Files / Ideas / 217
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Subject: 
Re: non-lego rendering using various LDraw tools
Newsgroups: 
lugnet.cad.dat.ideas
Date: 
Thu, 23 Sep 2004 19:41:49 GMT
Viewed: 
4610 times
  
In lugnet.cad.dat.ideas, Don Heyse wrote:
   In lugnet.cad.dat.ideas, Steve Bliss wrote:
   In lugnet.cad.dat.ideas, Don Heyse wrote: Yep, thanks for doing that. Then I turned around and installed Cygwin, so now I probably have gcc available -- I think.

I’d imagine so. I don’t actually use Cygwin. I use the mingw version of gcc on Windows because I don’t want to worry about the Cygwin unix compatibility DLL.

   Ha. Once you’ve got vertices and edges, writing the Triangle format is pretty straightforward. The only tricky bit (and one I did not solve) is telling Triangle the location of ‘holes’. If you have open spaces in your image, you have to tell Triangle, or it will happily pave over them.

It’s not too hard to detect holes while you’re vectorizing edges, just look at the pixel color above the highest point on each closed polyline. You can encode this by writing outside edges clockwise and inside edges counter-clockwise. I don’t remember if autotrace can do this. I’ll have to check.

Err, reverse course. I peeked at the autotrace source and it says in pxl-outline.c “Outside outlines are traced counterclockwise”. So if you want to make things easier for me, do it that way. ;^)

  
   I’ll happily share what I’ve done, especially if I ever finish it. But (working with Autotrace) you were probably were ahead of what I accomplished. But I’d be interested in looking at your code. :)

The autotrace source code for LDR output from May is here. I put the executable here, but I don’t remember how to run it. There’s a batch file I used to test it in the source zip file, but that might not have all the right options for a real world example.

Don



Message has 1 Reply:
  Re: non-lego rendering using various LDraw tools
 
(...) OK. My edges already were counterclockwise. :) Umm, for inside outlines (inlines?) to be clockwise, that's 'clockwise' from a global view, right? If so, then my inlines are already clockwise. But I don't know which ones are inlines, and which (...) (20 years ago, 23-Sep-04, to lugnet.cad.dat.ideas, FTX)

Message is in Reply To:
  Re: non-lego rendering using various LDraw tools
 
(...) I'd imagine so. I don't actually use Cygwin. I use the (URL) mingw> version of gcc on Windows because I don't want to worry about the Cygwin unix compatibility DLL. (...) It's not too hard to detect holes while you're vectorizing edges, just (...) (20 years ago, 23-Sep-04, to lugnet.cad.dat.ideas, FTX)

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