Just curious.... I want to know what 3d formats besides POV-Ray SDL 
support object instantiation.  So far as I'm seeing, .obj does not and 
yet seems like such a basic thing....  Am I wrong?  Know of a good place 
to compare formats?

Thanks in advance,
Charles

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> Just curious.... I want to know what 3d formats besides POV-Ray SDL 
> support object instantiation.  So far as I'm seeing, .obj does not and 
> yet seems like such a basic thing....  Am I wrong?  Know of a good place 
> to compare formats?
> 

I have no idea about instanciation specifically, but this page is a good 
start for plenty of data format:
http://local.wasp.uwa.edu.au/~pbourke/dataformats/

Hope this helps

-- 
Vincent

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4722fc09@news.povray.org...
> Just curious.... I want to know what 3d formats besides POV-Ray SDL 
> support object instantiation.  So far as I'm seeing, .obj does not and yet 
> seems like such a basic thing....  Am I wrong?  Know of a good place to 
> compare formats?

AFAIK, instantiation is not a property of the file format, but a feature of 
the renderer.

G.

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Gilles Tran wrote:

> AFAIK, instantiation is not a property of the file format, but a feature of 
> the renderer.

True. Although it helps if the file format has some way to express that 
the renderer should do this. (E.g., rather than just duplicating the 
data twice.)

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Gilles Tran <gitran_nospam_@wanadoo.fr> wrote:
> AFAIK, instantiation is not a property of the file format, but a feature of 
> the renderer.

  If you tell the renderer "copy this mesh 1000 times over the scene" (but
the mesh data is kept only once in memory), thus getting a nice scene, and
then you want to save this scene into a file, how do you do that if the
file format doesn't support saying "copy this mesh here" commands?

-- 
                                                          - Warp

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> Gilles Tran <gitran_nospam_@wanadoo.fr> wrote:
>> AFAIK, instantiation is not a property of the file format, but a feature of 
>> the renderer.
> 
>   If you tell the renderer "copy this mesh 1000 times over the scene" (but
> the mesh data is kept only once in memory), thus getting a nice scene, and
> then you want to save this scene into a file, how do you do that if the
> file format doesn't support saying "copy this mesh here" commands?
> 

Keeping it only once in memory is a feature of the renderer, which 
requires such a command on the file format. Having the triangle list 
only once in the input file is a feature of the file format. A (quite) 
stupid parser could duplicate data in memory even if it's not duplicated 
on the file!

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Nicolas Alvarez <nic### [at] gmailisthebestcom> wrote:
> requires such a command on the file format.

  That's what I thought.

-- 
                                                          - Warp

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Nicolas Alvarez wrote:

>> Gilles Tran <gitran_nospam_@wanadoo.fr> wrote:
>>> AFAIK, instantiation is not a property of the file format, but a 
>>> feature of the renderer.
>>
>>   If you tell the renderer "copy this mesh 1000 times over the scene" 
>> (but
>> the mesh data is kept only once in memory), thus getting a nice scene, 
>> and
>> then you want to save this scene into a file, how do you do that if the
>> file format doesn't support saying "copy this mesh here" commands?
>>
> 
> Keeping it only once in memory is a feature of the renderer, which 
> requires such a command on the file format. Having the triangle list 
> only once in the input file is a feature of the file format. A (quite) 
> stupid parser could duplicate data in memory even if it's not duplicated 
> on the file!

Basically I like the idea of having the flexibility of being able to 
export to a fairly universal format like .obj.   But if .obj doesn't 
support instantiation, and if my model is (or will be) a collection of 
tens if not (perhaps) hundreds of thousands of non-unique meshes (save 
the for transformation of each), then man oh man will that be a big 
file.  I can't imagine most file formats would leave out such a basic 
thing.

Anyway unless somebody can answer somewhat definitively about a good 
format, it looks like I've got some studying to do.  Paul Bourke's page 
that Vincent linked to looks useful especially with that handy search 
button.

Charles

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Vincent Le Chevalier wrote:

>> Just curious.... I want to know what 3d formats besides POV-Ray SDL 
>> support object instantiation.  So far as I'm seeing, .obj does not and 
>> yet seems like such a basic thing....  Am I wrong?  Know of a good 
>> place to compare formats?
>>
> 
> I have no idea about instanciation specifically, but this page is a good 
> start for plenty of data format:
> http://local.wasp.uwa.edu.au/~pbourke/dataformats/
> 
> Hope this helps
> 


Thanks!  This is definitely a good resource to know about.
Charles

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Charles C <"nospam a nospam.com"> wrote:
> Basically I like the idea of having the flexibility of being able to
> export to a fairly universal format like .obj.   But if .obj doesn't
> support instantiation, and if my model is (or will be) a collection of
> tens if not (perhaps) hundreds of thousands of non-unique meshes (save
> the for transformation of each), then man oh man will that be a big
> file.  I can't imagine most file formats would leave out such a basic
> thing.

A lot of older formats would have been dealing with very simple scenes (for an
example of a format that time has really left behind, look at .3DS). I guess
the use case for a lot of those formats was to hold a single model rather than
a scene. You want a modern interchange format; Collada springs to mind.

Tom

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