[Robotics] Collada 1.5

[Sébastien Barthélemy]

On Tue, Jul 20, 2010 at 10:27 AM, Izaak Van Crombrugge
<izaak.vancrombrugge at gmail.com> wrote:
> Indeed, there is some work going on with OpenCollada, but it is not easy to
> find any development info. And while all of blender is moving towards Python
> to make it more open, the Collada import/export has changed to C++.

Don't you think there might be a good reason to this change?

I think it is more important to use the right tool to do the job, than the right
programming language. opencollada is under active development, integrated
into mainstream tools and currently supported. It certainly seems a better
base to build upon than a 3 years old, unmaintained, deprecated (from Blender)
set of python class, no matter how python is great in itself.

> This means: no Collada update without rebuilding Blender.

Collada itself is not changing a lot. So I don't see this being a big problem.

> (Python code is more "inviting" than C/C++ what makes it "more open source")

Again, I think that a good C++ library is better and more inviting than an
incomplete and unsupported python one.

I think that task of (robustly) converting from one format to another is not
appealing at all in itself, I'm not sure writing it in python will make it fun.

It simply should work, and be rock-solid. No need to be fun.

> The biggest reason to make the importer ourselves is that Kinematics and
> Physics are no priority at all to be supported as the focus lies on the
> artistic, visual elements.

That might as well be a good reason to help them supporting these features
instead of working on yet another loader that won't support the
artistic elements.

> (http://wiki.blender.org/index.php/User:Chingachgook/Gsoc2009/End-User_Specification#File_format_support_completeness)

Thank you for the link.

> We will only put effort in the things that are relevant for robotics:
> The aim is to support: (ordered by priority)
> 1) Meshes and object structure
> 2) Armatures with kinematics (joints etc.) and Physics
> 3) Simple materials (colours and maybe simple textures)
> 4) Cameras, lamps,...
> Because Collada is quite extensive, we didn't start from scratch (thank
> God!). We use Grasp and ColladaImEx modules as basis.
> The Translator module will be written mostly from scratch, as Blender has
> changed too much.

I don't know about Grasp.

> But we are still examining the code to find out what we
> can still use. (What the translator is:
> http://colladablender.illusoft.com/cms/content/blogcategory/16/43/)
> If anyone has worked with this Translator code, we are listening! :)

I used it once, and found it no robust at all. It seemed to me that it was
written to convert a set of collada files (probably the one the author needed
to convert), not any collada file. Calling it a "collada loader" is IMHO abusive
as many valid collada files were not loaded correctly/at all.

If I remember well, it even produced invalid files (from the point of view of
coherencytest, which is quite pedantic).