Re: [Maya2osg-users] Discussion of next changes

[Jean-Sébastien G. <jea...@cm...>]

Hello Javier,

>    I don't know if we are understanding each other. My point is that
> you cannot add support for every attribute and attribute combination
> possible, and each user will have its own needs structured in its own
> way, maybe incompatible among them and doesn't seem to be a good place
> to implement that kind of thing the plug-in C++ code.

I understand your point, but I don't see an unlimited amount of 
attributes. Essentially, there are a fixed number of things that will be 
useful to users once the scene is exported. I will have mine and others 
will have theirs which might not be the same set, sure, but once they 
are done they are done.

I see it as the role of the plugin to specify what it exports (at least 
a base set). If the user wants more than that, sure he can write a 
pre-export script to get out other things, but the basic set should be 
fairly complete. If you don't agree with this point then I guess I'll 
just write a pre-export script, so I just need to add code to maya2osg 
that will export notes into OSG node descriptions and we'll be done.

>    Are you sure? Please, post a real example of the information you
> want to retrieve from the Maya scene and where do you read it and
> where do you want to write it.

For example, for a material (say a Blinn/Phong), the osg::Material 
already contains the diffuse color, specular color, shininess, etc. Plus 
there is a diffuse texture in the same StateSet as the Material.

But if the user attached a texture to the bump attribute, I would need 
the filename of the texture, the amount of bump it contributes, and the 
coordinate space it is used in (bump = object space, normal = tangent 
space generally).

Likewise, if the user attached a texture to the specular attribute, 
that's a specular map, and we could export again the texture and the 
amount of contribution.

Since the exported information contains these different types of maps, I 
don't see any harm in putting the diffuse texture there either, just for 
completeness.

So I would add to the OSG node description this kind of string:

<maya2osg_material>
Material_name Diffuse <filename> <amount>
Material_name Normal <filename> <amount> <coordinate space>
Material_name Specular <filename> <amount>
</maya2osg_material>

or more concretely:

<maya2osg_material>
Ship_hull Diffuse textures/ship_hull_d.jpg 100
Ship_hull Normal textures/ship_hull_n.jpg 100 tangent
Ship_hull Specular textures/ship_hull_s.jpg 30
</maya2osg_material>

I would prefer this kind of string never be visible / editable by the 
user, since it's already specified by the Maya material. Putting it in 2 
places (and one which the user could just delete if they're not paying 
attention) is asking for trouble.

In general, artists are not programmers, they have their own workflow 
and if they build their scene in Maya so that it looks like they want, 
then the exporter should export that correctly without needing other 
operations / scripts.

For comparison, here's what was recently added to the 3DSMax exporter 
(OSGExp) to do the same thing:

---------------------------------------------------------------------
I've just committed support for the material description strings. Each 
material will have its own description string added to the root node. 
Here is a sample description:

# osgmaxexp material data
Name	Basketball
Map	Diffuse	0	1	images\bball_diffuse.jpg
Map	Bump	1	0.3	images\bball_normal.jpg	
---------------------------------------------------------------------

(the separator they chose is tab)

I think something similar would work. The only remaining point really is 
whether the plugin creates this string or a pre-export script does.

>    The reason to put it in the notes is to have a transparent way of
> specifying whatever you can send and to what OSG node exactly.

As I said, exporting notes is fine and IMHO is orthogonal to exporting 
attributes in the scene. If the artist put notes in the notes field in 
Maya, they should be exported as OSG node descriptions. This does not 
affect the discussion above. Rather, if exporting notes is added to the 
plugin, and we decide that what I want above will be done by a 
pre-export script that adds text to the notes, then we are done and I 
can start using it immediately.

Thanks,

J-S
-- 
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Jean-Sebastien Guay    jea...@cm...
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