Subject:
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Re: A comprehensive LDraw object model
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Newsgroups:
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lugnet.cad.dev
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Date:
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Mon, 11 Feb 2002 22:00:25 GMT
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Viewed:
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661 times
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Anders Isaksson wrote:
> "Kyle McDonald" <kmcdonald@bigfoot.com> skrev i meddelandet
> news:3C671582.8010404@bigfoot.com...
>
> > [...Occlusion culling...]
> > You could take this to the extreme and even try to tag the geometry
> > based on whether it is part of the top, bottom, front, back, left,
> > right, or inside of the part.
>
>
> If the parts are BFC compliant, there's no need to tag for 'top', 'left' etc.
> as this information is already there in the surface normal (with much better
> detail!).
Well again BFC is only useful for culling surfaces that face away from
you. It doesn't really do anything for faces that face you but are
blocked by other faces. When I talked about top, left, right, etc, I
was envisioning some system by which an application could decide not
to try to fraw the left or top side of a brick when it knew there was
another brick right up against (and therefor covering) that side.
This is a common scenario when discussing models made from LEGO. :)
But like I said in that message, I'm not sure the effort would really
be worth it.
>
> Tagging for 'inside', 'outside' could be useful. In BlockCAD I can tag each
> polygon/line with a 'detail level' value - if the renderer is set to level 1,
> no polygons (or lines) with a higher detail level are drawn. In BC this is
> mainly used to draw a block with/without decoration.
Steve mentioned the Detail level also. I replied to that already.
But your 'levels' below give something more concrete to talk about.
> The typical levels for LDRAW parts could be:
>
> 0 - wireframe outline
> 1 - outside surfaces
> 2 - studs outside surfaces
> 3 - inside surfaces
> 4 - ???
Using something like this would do basically what I'm talking about.
Although when Steve first mentioned 'Detail' levels, I started thinking
about something where even the outside was split into different levels
of detail. Of course that might not be useful on the majority of bricks.
I just wasn't sure you could come up with one detail priority scheme that
might apply to everything. I thought maybe having both 'outside' with
Detail levels, and 'inside' with it's detail levels would be more
flexible. But I could be wrong. ;)
> But it's a big job going through all parts, and add the tag information, it's
> probably better to try to deduce inside surfaces with a program.
I've been thinking about how a program could do that on the fly.
I haven't come up with anything yet, and I'd be intrested in hearing
any ideas anyone has :)
-Kyle
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Message is in Reply To:
 | | Re: A comprehensive LDraw object model
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| "Kyle McDonald" <kmcdonald@bigfoot.com> skrev i meddelandet news:3C671582.801040...oot.com... (...) If the parts are BFC compliant, there's no need to tag for 'top', 'left' etc. as this information is already there in the surface normal (with much (...) (23 years ago, 11-Feb-02, to lugnet.cad.dev)
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