Handling object groups in collada exporter/importer #53966

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Gaia Clary · 2018-01-31T21:48:37+01:00

Gaia Clary commented

2018-01-31 21:48:37 +01:00

In Blender a group is just a collection of objects unrelated to the object relationship. Apparently Group instances are made of an empty plus instances of the group objects. This blend file contains a group made of 3 simple objects and one group instance:

group_export.blend

The Suzanne group in this file is made of 3 objects: "Suzanne", "Pole" and "Base"
When exporting this we can make use of Collada library nodes as follows:

'''
<library_nodes>

  <node id="Group-Suzanne" type="NODE">
      <node id="Suzanne" type="NODE">
          <instance_geometry url="#Suzanne-mesh"/> 
      </node>
      <node id="Pole" type="NODE">
          <instance_geometry url="#Pole-mesh"/>
      </node>
      <node id="Stand" type="NODE">
          <instance_geometry url="#Stand-mesh"/>
      </node>
  </node>

</library_nodes>

<library_visual_scenes>

  <visual_scene id="Scene">
      <node id="Suzanne-Instance" type="NODE">
          <instance_node url="#Suzanne-instance"/> <!-- placed at the location of the instance -->
      </node>
  </visual_scene>

</library_visual_scenes>

'''

When importing this, then basically the blend file is reconstructed like the original with one group made of the library nodes and one group instance referring to the group.

caveats

What to do when the user has selected the group instance and the objects in the group.
How to handle the situation where objects are in multiple groups.
Should we also take care of the layers where each object is placed? I think that is doable as well.

Is there anything else to consider? Opinions and suggestions are welcome :)

Thanks
Gaia

In Blender a group is just a collection of objects unrelated to the object relationship. Apparently Group instances are made of an empty plus instances of the group objects. This blend file contains a group made of 3 simple objects and one group instance: [group_export.blend](https://archive.blender.org/developer/F2061340/group_export.blend) The Suzanne group in this file is made of 3 objects: "Suzanne", "Pole" and "Base" When exporting this we can make use of Collada library nodes as follows: ''' <library_nodes> ``` <node id="Group-Suzanne" type="NODE"> <node id="Suzanne" type="NODE"> <instance_geometry url="#Suzanne-mesh"/> </node> <node id="Pole" type="NODE"> <instance_geometry url="#Pole-mesh"/> </node> <node id="Stand" type="NODE"> <instance_geometry url="#Stand-mesh"/> </node> </node> ``` </library_nodes> <library_visual_scenes> ``` <visual_scene id="Scene"> <node id="Suzanne-Instance" type="NODE"> <instance_node url="#Suzanne-instance"/>  </node> </visual_scene> ``` </library_visual_scenes> ''' When importing this, then basically the blend file is reconstructed like the original with one group made of the library nodes and one group instance referring to the group. ## caveats * What to do when the user has selected the group instance and the objects in the group. * How to handle the situation where objects are in multiple groups. * Should we also take care of the layers where each object is placed? I think that is doable as well. Is there anything else to consider? Opinions and suggestions are welcome :) Thanks Gaia

Gaia Clary self-assigned this 2018-01-31 21:48:37 +01:00

Gaia Clary commented

2018-01-31 21:48:37 +01:00

Added subscribers: @GaiaClary, @mont29

Sergey Sharybin commented

2019-04-10 10:19:36 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2019-04-10 10:19:36 +02:00

@GaiaClary, seems this slipped through the cracks. Is it still relevant for the 2.80 with the new instancing based on collections?

Gaia Clary commented

2019-04-10 13:57:02 +02:00

Ops... i completely forgot about this one :( I guess we can get this to work in 2.80 :)

Oscar D Lezama commented

2019-10-17 16:13:16 +02:00

Added subscriber: @Raincry

Oscar D Lezama commented

2019-10-17 16:13:16 +02:00

Hi, The .DAE exporter is still not working as intended, the Use Object Instances option is not making instances at all and the objects get exported in one big collection with no hierarchy.
The file is not getting that </library_nodes> section as described before.

Thanks for any possible help here :)

Hi, The .DAE exporter is still not working as intended, the Use Object Instances option is not making instances at all and the objects get exported in one big collection with no hierarchy. The file is not getting that </library_nodes> section as described before. Thanks for any possible help here :)

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Handling object groups in collada exporter/importer #53966

caveats