POV-Ray : Newsgroups : povray.programming : Parsing mesh2 data : Re: Parsing mesh2 data Server Time
18 Sep 2021 05:43:48 EDT (-0400)
  Re: Parsing mesh2 data  
From: clipka
Date: 14 Sep 2016 05:21:17
Message: <57d9168d@news.povray.org>
Am 14.09.2016 um 10:08 schrieb Mr:
> clipka <ano### [at] anonymousorg> wrote:
>> Fun fact:
>>
>> Trying to read obj files directly turns out to be only marginally faster
>> than parsing mesh2 data (about 3% as it seems).
> 
> Interesting! Too bad it's not alembic files which, as a caching format, will
> probably benefit from a simpler/faster export flow...

Uh, I'd rather not. With Alembic being a quite modern format, users may
expect support for a few more features than just polygon meshes, such as
NURBS and things, and supporting those would be a _lot_ of work. OBJ, on
the other hand, is old enough that people know better than to expect
such bells and whistles to work with all software.

Also, I haven't yet found /any/ documentation whatsoever about the file
format itself, only a ready-made library; so implementing even a tiny
bit of it would require more than the mere ~500 lines of code I added
for OBJ import; it may also suffer in speed from additional code
required to convert the data structures provided by the library to those
used by POV-Ray internally.

> Still OBJ is interesting! do you think it would be worth exporting Blender mesh
> geometry to OBJ instead of Mesh2 or rather let you investigate and optimize the
> mesh2, so that it will then be even faster ! :-) ?

When it comes to import speed, I would suspect OBJ to maintain a slight
advantage over mesh2, because the formats are reasonably similar in
structure, with OBJ being just that little bit less verbose(*). Mesh2
parsing /per se/ cannot be reasonably sped up any further as it uses
POV-Ray's general parser infrastructure (by contrast, OBJ import
accesses the file directly; which also means that you can't generate OBJ
data "on the fly" procedurally, like you can with mesh2 data, except by
the tedious process of writing a temporary file). Any potential for
speedup of mesh2 parsing is in pieces of code that OBJ import would also
benefit from.


(* Or at least it has the potential to be, if exporters group the
triangles by material before writing them. If material changes
frequently between consecutive triangles in the OBJ file, the format can
get /very/ verbose.)


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