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 CAD / Development / 10122
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Subject: 
Re: BFCFixer
Newsgroups: 
lugnet.cad.dev
Date: 
Thu, 3 Feb 2005 10:37:50 GMT
Viewed: 
2325 times
  
In lugnet.cad.dev, Chris Dee wrote:
In lugnet.cad.dev, Mark Tarrabain wrote:
Don Heyse wrote:
But wait, If you can make a program to fix winding on the fly then make
a tool for ldraw.org so it can be added to the part submission process.
Then we can run it on all the parts so nobody ever has to fix them on
the fly again.  That'll make *all* the renderers faster.

Well, I had some spare time today... so I wrote one.

I may be being dense here, but I dont understand how this can be done
programatically.

I think it can be done for simple objects, by choosing a random winding for 1
polygon, then processing all touching polygons so they're wound the same way
(when looking from the same side - out ot in). This would produce a result that
is entirely right, or entirely wrong (in which case it can be fixed by changing
the winding direction in the 0 BFC statement). It may even be possible to work
out which way is "out" on simple objects.

More complex objects may cause that algorithm to fail, as Mark alluded to, but I
think the main reason you wouldn't want renderers using such an algorithm is
speed - I think it would seriously slow down an already intensive process.

I would certainly be interested to see how this program handles some of the more
complex DATs out there.

ROSCO



Message has 1 Reply:
  Re: BFCFixer
 
(...) Of course, it's that simple - thanks. Except some of the most basic LDraw parts (regular bricks) fail this test because the studs are "stuck on" a complete quad, rather than a surface peppered with stud-sized holes. Chris (20 years ago, 4-Feb-05, to lugnet.cad.dev)

Message is in Reply To:
  Re: BFCFixer
 
(...) I may be being dense here, but I dont understand how this can be done programatically. The point of BFC is to allow renderers to understand if a particular polygon is facing the camera or facing away from it. If all polygons are wound (...) (20 years ago, 3-Feb-05, to lugnet.cad.dev)

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