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Subject:
Re: NURBS primitive?
Date:
Sat, 04 Mar 2000 03:13:51 -0800
From:
Ken <tyl### [at] pacbell net>
Reply-To:
lin### [at] povrayorg
Organization:
Tyler Engineering Services
Newsgroups:
povray.unofficial.patches
References:
1 , 2 , 3
David Curtis wrote:
>
> In article <38C06E3A.9D90DCC4@pacbell.net>, lin### [at] povrayorg wrote:
> >> if not, how hard would it be to add it?
> >
> >Techically it is possible. The question you need to ask is how useful
> >would it be.
>
> Sorry Ken, IMO that sounds like saying "why put in airbags when we already
> have seatbelts."
I have heard many arguments for and against and so far the consensus seems
to favour not including them in POV-Ray. Yours is the first I have heard
where better quality is mentioned. Most argue in favour of smaller file
sizes than their triangle counterparts.
> I checked out a program last night called Lightening3d. It exports NURBS to
> POV by converting to bezier patches. Sounds cool. Maybe this is the way that I
> could go?
Patches have the advantage that you can change the smoothing of the patch
by changing a single parameter. The drawbacks to this is the amount of parse
time needed. The greater the amount of tessellation of the patch needed to
achieve the desired smoothness will add to the time it takes to parse each
patch. File sizes may tend to be a bit smaller but the trade off in file
size will be parsing time.
For what it is worth I have rendered some enormous mesh files with as
many as a million triangles before and the the parsing time was not in
my opinion all that prohibitive. I have had while loops with much fewer
objects take considerably longer than a huge triangle mesh file takes
to parse and the memory requirement for while loops are much greater.
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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