Hello,

I would like the plugin to support the "Layer" animation in blender.

ex: node A is contained in layer "L0" from frames 0 to 10 and then is in layer "L1"...

Like this, i would be able to have objects appearing / disapearing from existing layers (very usefull for game programming ...)

However, i do not know if the collada spec supports this kind of thing ...
(Blender supports it anyway)

Hi there, I'm trying to use Blender with the 3D engine Horde3D and I would really like to be able to import skinned animations from Blender to Horde via collada. A description of the problem can be found here: [www.nextgen-engine.net]

The Horde "colladaConv" importer program isn't very generally written and only works with collada files exported from max or maya (using the FCollada library) with the "bake matrices" option enabled. So although some of the fault lies with "colladaConv" I think the collada blender plugin is not far from being compatible with Horde.
I started to look into how to modify the collada plugin but I soon gave up due to the complexity of the plugin and my limited understanding of collada and blender.
(Sidenote: As much as I like Python, the lack of type declarations actually makes it harder to dig into a large foreign code base imo.)

So this is what I came up with:
line 1217 in collada.py should be changed from:
AppendTextChild(node,i[0],val)
to:
SetAttribute(AppendTextChild(node,i[0],val), DaeSyntax.SID, "transform")
For example, this will change exported nodes from:
<node layer="L2" sid="Root" type="JOINT" id="Root" name="Root">
<matrix>
-1.0 0.0 0.0 -0.00047
...
to:
<node layer="L2" sid="Root" type="JOINT" id="Root" name="Root">
<matrix sid="transform">
-1.0 0.0 0.0 -0.00047
...

This will make "bake matrices" work just like FCollada and allow them to be compatible with Horde.

Then comes the hard part:
All bone animation IPO:s should not merely be exported as they are, they should be merged into one animation channel which uses matrices and targets the <node-name>/transform. For example, a two frame animation which animates a "LeftUpLeg-node" node:
<animation id="LeftUpLeg-node-transform">
<source id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-input">
<float_array id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-input-array" count="2">0 0.04</float_array>
<technique_common>
<accessor source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-input-array" count="2" stride="1">
<param name="TIME" type="float"/>
</accessor>
</technique_common>
<technique profile="MAYA">
<pre_infinity>CONSTANT</pre_infinity>
<post_infinity>CONSTANT</post_infinity>
</technique>
</source>
<source id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-output">
<float_array id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-output-array" count="32">-0.786355 0.617776 0.000000 -5.83286 -0.617776 -0.786355 0.000000 -0.923933 0.000000 0 1 -11.6415 0 0 0 1 -0.45474 0.890625 0.000000 -5.83286 -0.890625 -0.45474 0.000000 -0.923933 0.000000 0 1 -11.6415 0 0 0 1</float_array>
<technique_common>
<accessor source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-output-array" count="2" stride="16">
<param name="TRANSFORM" type="float4x4"/>
</accessor>
</technique_common>
</source>
<source id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-interpolations">
<Name_array id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-interpolations-array" count="2">LINEAR LINEAR</Name_array>
<technique_common>
<accessor source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-interpolations-array" count="2" stride="1">
<param name="INTERPOLATION" type="Name"/>
</accessor>
</technique_common>
</source>
<sampler id="LeftUpLeg-node-transform_LeftUpLeg-node_transform-sampler">
<input semantic="INPUT" source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-input"/>
<input semantic="OUTPUT" source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-output"/>
<input semantic="INTERPOLATION" source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-interpolations"/>
</sampler>
<channel source="#LeftUpLeg-node-transform_LeftUpLeg-node_transform-sampler" target="LeftUpLeg-node/transform"/>
</animation>

The above output is from 3ds max; of course, the collada blender plugin doesn't have to output just like this, I think the important part is the <channel ... target = "LeftUpLeg-node/transform"/> tag and the float array of 4x4 bone node transforms.

I was thinking of modifying translator.py/Animation.SaveToDae so that it goes through all the generated IPO-curves if "bake matrices" is on and generates matrices for them, multiplies the matrices together and puts them in a new curve which has as many key frames as the "union of the other curves' key frames" if you understand what I mean. But I figured that I wasn't the right person to do it since I don't really understand the code.

Also, there is one more problem: the "Warning: Mesh Businessman_002 is directly attached to a joint; use skin instead!" warning. I think this is the same thing as another thing I noticed: I exported an animated mesh from blender without "bake matrices" and imported this .dae into 3ds max. The mesh imported alright, the bones and the animation of the bones too. But: the mesh wasn't joined to the bones anymore (no skinning) and the mesh was misplaced (by the inverse of the root bone position I think). I don't know how to fix this problem, but it might be solved just by removing the link between the skinned mesh and the root bone when exporting to collada maybe?

Anyhow, I might be way off with my proposed solutions since I only have a very shallow understanding of the exporter and collada in general. Perhaps they can be of some help at least. Thanks for the great work with the collada plugin, hopefully these problems can be fixed!

This is very sad.

I saw the announcement for this exporter enhancement when it came out, and I made my own skeletal animation system, with custom Gui to add joints, etc., to hold me over until Pieter finished the work which he already begun at that time. Now it seems that Illusoft and Pieter completely dropped this product 1 1/2 years ago.

I am willing to pick up development of the armature export piece (hopefully followed by animations of the armatures), but I just don't have time to learn everything about the design of this exporter if there is nobody in the world to answer technical questions I may have. Is anybody out there knowledgeable enough and willing to help answer design questions about the exporter, so I can concentrate on learning it quickly and enhancing it?

Sorry if this is a total nube question. I just stumbled upon this site was looking for further information on how I may import BVH MOCAP files into the latest version of blender. Is Collada replacing this functionality? The reason I ask is that I just purchased a turn key MOCAP setup and was really hoping to use it with blender. Will they be bringing back this BVH import / export feature? If someone could point me in the right direction with other links for me to get working on I'd really appreciate it.

Thanks.

Blaine is right; it's a damned shame to see this exporter languishing in an unfinished state, when so many users (myself included) were drawn to Blender in part by its support for Collada. Perhaps Pieter would consider formally handing over its development to a team of volunteers? I'd be more than happy to contribute, and I see several others have expressed an interest as well.