 | | Clipping / CCW / CW / INVERT [DAT]
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First, let me apologise, if you get this message twice. It seams that the old e-Mail address (L-CAD@LISTSERV.UH.EDU) does not work completelly. Because I got the message back, but couldn't see it in www.lugnet.com/cad/dev note: i am subscribed in (...) (25 years ago, 6-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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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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| | Re: Clipping / CCW / CW / INVERT
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(...) 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... ) (...) (25 years ago, 7-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) Thanks! (...) I knew that ! ;) (...) LDraw doesn't, but this specification is for new Programs which are backwards compatible with Ldraw, but with a bunch of new enhancements. Check the instructions of any LEGO MODEL and you will see an (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) 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)
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| | Re: Clipping / CCW / CW / INVERT
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Rui Martins wrote in message ... (...) You mean six of one, half a dozen of the other. :) (...) it (...) Using 0 FACE CW|CCW|DS|UNKNOWN will also keep backward compatibility. Either way though, some quadrilaterals will need to be manually tweaked (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) 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)
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| | Re: Clipping / CCW / CW / INVERT
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(...) No, thank you! (...) I don't know if I knew you knew that, but I was almost positive you knew that. And I knew most everyone else knew that, but I wasn't sure absolutely everyone knew that. ;) (...) Right. New programs may handle transparency (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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On Wed, 6 Oct 1999 18:15:40 GMT, Rui Martins <Rui.Martins@link.pt> wrote: Follow-up note: the more I look at this, the more I like using WINDING / CLIPPING instead of FACE. For reasons listed by Rui, for more flexibility, for the ability to enable (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) touche'! (...) Not exactly! If the color has any transparency, force CLIPPING OFF, irrespective of what the file TAGS inform. (SIDE NOTE) when using the tag 0 CLIPPING ON you are not informing the program that it MUST do clipping, but instead (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) I don't need the WINDING UNKNOWN, since it's redundant with CLIPPING OFF. When clipping is OFF you don't care the state of the winding. I am curious, what is CLIPPING -1 ? an UNKNOWN, CLIPPING when not found is assumed as OFF (the safe side), (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) No, when I look at the images I see real alpha-blended surfaces :) I've tried to turn backface culling in the transparent parts and they looked very ugly, it's better to draw everything in those cases. (...) Just a note to correct the (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) I put in WINDING UNKNOWN because it explicitly states that the winding is unknown (and probably bad). This way, you can effectively disable clipping for a particular section of (unchecked) code, without having to force clipping back on at the (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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Isn't a CLIPPING tag redundant? Programs should always clip when drawing an opaque part, and never clip when drawing a transparent part. -Gary (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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(...) Do you know the reason why? The change-state-calls could cost a little overhead, but don't they just set some flags? And these flags would just cause negating an orientation test? /Lars (25 years ago, 9-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) I once asked the same question :) Most OpenGL drivers have part of the rendering code create at runtime instead of having if/else statements for all the possible flags. When you change the state, the driver has to rebuild the code again and (...) (25 years ago, 9-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) Nope, CLIPPING is not redundant; using CLIPPING and WINDING is another way of accomplishing what we've been discussing with the FACE meta-statement. See Rui's description in the root-message of this thread. Also, clipping should not be (...) (25 years ago, 11-Oct-99, to lugnet.cad.dev)
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| | Re: Clipping / CCW / CW / INVERT
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(...) Right. But that happens at rendering time, not in the description language. (...) I knew that. ;) (...) LOL Steve (25 years ago, 11-Oct-99, to lugnet.cad.dev)
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