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 CAD / Development / 3057
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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.SAYNOTOSPAMcom
Viewed: 
403 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 (25 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 (25 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 (...) (25 years ago, 7-Oct-99, to lugnet.cad.dev)

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