[Opensim-users] Collada

[Toni Alatalo]

Dzonatas kirjoitti:
> http://www.collada.org/mediawiki/index.php/Portal:Conditioners_directory
> I'd imagine you wonder about how to go from a mesh to a parametric model 
> (if the external application doesn't support all the parametric data).
>   

and back. i don't think there is a sensible way for such a roundtrip, 
e.g. for bringing SL data to vanilla Blender for editing. what good 
would prims converted to meshes do you in a modelling app? i guess you 
can get them today with the meshmerizer if you want. but that way you 
won't be able to edit them for loading back to SL, so i see no use.

> Blender could be extended to support the same parametric data that is 
> used in SL/opensim. http://www.google.com/search?q=blender+parametric
>   

that would be possible, if you really wanted to use Blender (or some 
other app) for SL building, but not a small job.

> For example, maybe include a script in the DAE file that generates the 
> mesh from the parametric data. The applications collada plug-in could 
> run the script any time the parametric data is modified to regenerate 
> the model. This is not too different of an idea from being able to store 
> shaders in the DAE file, which exists now.
>   

what would that script run against, and how would the parametric data be 
modified?

it would in principle possible to include e.g. Blender script code 
there, and make a tool for Blender that could edit that data. the major 
2.5 refactor that's well under way should make it easier to do such 
custom tools soon. but this all would be Blender specific, and would 
have basically nothing to do with Collada anymore. it would be possible 
to include that data in a DAE file, but i don't see any benefit there 
really, as it would be a custom solution for dealing with a specific 
kind of data (SL prims) in a specific application (Blender).

to summarize my understanding of these talks:

1. someone wanted a way to store objects from OpenSim to a file, to be 
able to send them to people etc. AFAIK that exists with the current 
serialization that has been in place for as long as i know, i don't know 
what the UI for it is but have seen the code :) .. and heard that people 
use it to put prims on the web etc.

2. Mikko Pallari and Adam Frisby have just now worked on a new version 
of that serialization, that would not depend on versions of the OpenSim 
code anymore (the previous code uses the automatic .net serialization so 
changes in the code structure break backwards compatibility with old xml 
files, but the new is made manually and decoupled from the code 
structure so also old files should work with future versions of OpenSim. 
i've been told that so far the code there hasn't been changed a lot 
exactly to remain compatible with old data files).

3. Collada does not support SL data. The scene hierarchy could probably 
be converted ok. For prim geometry data you could define own extensions, 
using the <extra> tags, for describing the modelling like the custom 
OpenSim format does now. This might work for opensim-to-opensim 
transfers, but so does the own custom format so there'd be no benefit. 
No other application would out-of-the-box know anything about those. If 
someone wants to use a modelling app to work on SL prims, they could add 
support for such a format in some existing parametric modelling app -- 
if it happens to be compatible enough with the SL model -- or add param 
modelling / SL data support to e.g. Blender. But also here it might be 
simpler to add support for the OpenSim format, than e.g. to modify the 
Collada importer, to get SL support. Anyhow if someone does this kind of 
work they are of course free to do as they see best. So far I don't see 
anyone actually working on this, and it's not a small job either.

Someone asked for my strategy for dealing with 3d data. Well for us at 
Playsign it's pretty simple, we have models made for games and some 
other things, and the plan has been to keep everything in Blender 
trusting that we can import anything and export to everywhere from 
there. I've participated in Blender development myself so it's easy to 
trust it. So far have used mostly Soya3d and Ogre, for which there are 
direct exporters, and looked at e.g. Papervision3d (that would use via 
the Collada export). There is also an Ogre importer. We don't use SL, 
but are looking at Rex and working on it 'cause might be able to use it.

The SL prims and parametric modelling in general (procedural trees and 
plants, but perhaps also cities and walls and whatnot) are interesting 
though and there's very much potential for the richness of VWs there. I 
don't know how good the SL model actually is, and hence how good it 
would be have parametric modelling in Blender similar to that, or how 
similar it is to whatever there is in existing procedural modelling 
apps. Looking forward to learn more about that next year, but off for 
holidays now! :)

cheers,
~Toni