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Subject: 
Re: Clipping / CCW / CW / INVERT
Newsgroups: 
lugnet.cad.dev
Date: 
Thu, 7 Oct 1999 21:32:26 GMT
Reply-To: 
lpieniazek@novera.comSPAMCAKE
Viewed: 
1374 times
  
Steve Bliss wrote:
> 
> Lots of good stuff in your post, Rui!
> 
> On Wed, 6 Oct 1999 18:15:40 GMT, Rui Martins <Rui.Martins@link.pt> wrote:
> 
> > So if a solid object is Opaque, then from any view point there are some
> > faces that are invisible, because they are facing away from the viewer.
> 
> (Side note: there are not actually any solids in LDraw. Only lines and
> polygons).
> 
> > From this we now know that "Opaque solids" can have some faces "Clipped"
> > and that transparent object (solid or not) CAN'T have any faces clipped.
> 
> Actually, since LDraw doesn't do shading, transparent surfaces *can* be
> clipped.  Only edges, the top-most solid surface, and the top-most
> transparent surface will show up in the final rendered image.

I believe this is incorrect, no? ALL transparent surfaces should appear,
if only to make a contribution to the color that underlying surfaces
appear to be (consider a trans blue surface in front of a trans yellow
in front of a white... )

Although I think LDraw and LDLite do not model this effect, some other
program might. POVRay does, right? But it doesn't benefit from clipping
unless you have reflection turned off.

--
Larry Pieniazek larryp@novera.com  http://my.voyager.net/lar
- - - Web Application Integration! http://www.novera.com
fund Lugnet(tm): http://www.ebates.com/ ref: lar, 1/2 $$ to lugnet.

NOTE: Soon to be lpieniazek@tsisoft.com :-)



Message has 2 Replies:
  Re: Clipping / CCW / CW / INVERT
 
(...) I agree with this. (...) that' wright, a program supporting transparent colors correctly (using alpha blending) would do this just wright. A 3D card here would do wounders ! (did I spell that wright?) (...) Agreeing again! Rui Martins (27 years ago, 8-Oct-99, to lugnet.cad.dev)
  Re: Clipping / CCW / CW / INVERT
 
(...) I was just pointing out that the clippability of transparent surfaces is a feature of the rendering program, and shouldn't be assumed in the description language. Steve (27 years ago, 8-Oct-99, to lugnet.cad.dev)

Message is in Reply To:
  Re: Clipping / CCW / CW / INVERT
 
Lots of good stuff in your post, Rui! (...) (Side note: there are not actually any solids in LDraw. Only lines and polygons). (...) Actually, since LDraw doesn't do shading, transparent surfaces *can* be clipped. Only edges, the top-most solid (...) (27 years ago, 7-Oct-99, to lugnet.cad.dev)

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