Collada

The COLLADA™ module has been implemented as a flexible tool for exporting and importing .dae files. A design goal is to provide a set of parameters which should make it possible to export/import Collada files from/to a variety of tools. But please be aware that the Collada module is still a work in progress. So it may be possible that your particular usage scenario is not yet supported.

Collada Exporter

../../_images/files_import-export_collada_export.png

Operator Presets

There are two operator presets (see top of Operator panel) for Second Life (SL) users:

  • Second Life Static – is good for exporting static meshes.
  • Second Life Rigged – is good for exporting the SL default character.

Special Notes for Second Life users:

  • Please use the Operator presets. All other export settings will not work for Second Life.
  • The character orientation needs to be such that the character looks towards positive X.
  • Scale and Rotation must be applied before the export!

Export Data Options

Apply Modifiers

All active modifiers will be applied in a non-destructive way. That is, the modifiers will be applied to copies of the meshes. Thus you no longer need to apply your modifiers before exporting. That is now done automatically in the background.

Consejo

Some modifiers provide a preview mode and a render mode with different mesh settings. The module now support both modes when applying the modifiers.

Selection Only
When Selection Only is enabled, then only the selected objects will be exported. Otherwise the entire scene is exported with all visible and all invisible objects.
Include Children

When this option is enabled then all children of the selected objects will also be exported regardless of their selection state.

Consejo

You now can select only an armature, then in the exporter enable Include Children then all rigged meshes attached to the armature will also be exported.

Include Armatures

When this option is enabled, then all armatures related to the selected objects will also be exported regardless of their selection state.

Consejo

You now can just select your objects, then in the exporter enable Include Armatures then the armature data is also exported.

Include Shape keys
This option also includes the application of shape keys! So now you can export your meshes with the current shape key configuration baked in.

Texture Options

Only Selected UV Map
When your mesh contains multiple UV layers, then Blender exports all layers by default. This option allows you to only export the active (selected) UV layer.
Include Textures
Blender supports two ways to add textures to your objects.
Copy

When you export images either material based image textures, then the exporter creates absolute file references in the export file.

But if the Copy option is enabled, the exporter will create copies of the images instead and place the copies besides the export file. In that case the file references are made relative.

Armature Options

Deform Bones Only
When this option is enabled, then the exporter strips all non-deforming bones from the exported armatures. This option is useful when your armatures contain control bones which are not actually part of the character skeleton. For example you can now export the Avastar rig with this option enabled. The resulting exported rig is compatible to Second Life. But please note the restrictions further below.
Export to SL/OpenSim

This option is very special. In fact some issues with bone orientation are calculated differently when this option is enabled. This is only relevant for rigged meshes. This option might be replaced by something more meaningful in the future (and will be still compatible to Second Life).

This option is only important when you want to export rigged meshes. For static meshes it just does nothing at all.

Collada Options

Triangulate
The mesh can be triangulated on-the-fly. The triangulation is based on the same function which is used in the Triangulate Faces tool for triangulating the current selection of faces. For full control over the triangulation you can do this manually before exporting. However this option allows to do the triangulation only for the exported data. The mesh itself is not affected.
Use Object Instances
In Blender you can reuse the same mesh for multiple objects. This is named «object instantiation». When you enable this option, then Blender will propagate object instantiation to the Collada file.
Use Blender Profile
Collada can be extended with tool specific data (profiles) Blender has its own (not official) profile that allows to export rig information into the Collada file, that can later be used to reconstruct the rig should it ever be necessary to import a dae file back into Blender.
Transformation Type
Collada supports two types of transformation matrix specifications. Either as <Matrix> or as a set of transformation decompositions (for move, rotate and scale). Note that the exporter will not strictly follow this option setting, but will rather take it as a hint to use the option if ever possible. This is so because some of the exported data types have specific rules about how the transformation matrix has to be exported. This is ongoing development and a less ambiguous method may be provided in the future.
Sort by Object Name
The export order of data is bound to internal object order and it can not be influenced in a reliable way. this option ensures that the Geometry nodes and the Object nodes are both exported in alphabetical order.
Keep Bind Info

When a rig is imported to Blender, then the rig’s bind pose will be used as Blender’s rest pose. So all Matrix information of the original rest pose is lost. But in some cases you may want to preserve the original rig information. The new option Keep Bind Info checks each bone for having two arrays:

  • rest_mat – an array of 16 floats which represent the bone’s original rest-pose matrix.
  • bind_mat – an array of 16 floats which represent the bone’s original bind-pose matrix.

If the arrays are present, then those arrays will be used instead of the current rest pose/bind pose. Those two arrays are either created by a previous Collada import (see Collada Importer below), or they can be created manually, or by an add-on (script based).

Collada Importer

../../_images/files_import-export_collada_import.png

The Collada importer is mostly driven by the imported data. There is one option for controlling the import units:

Import Units
If not enabled the imported data will be rescaled according to the currently used unit system. if this option is enabled, then Blender will adjust itself to the unit system as provided by the Collada file.
Fix Leaf Bones

Collada only records «joints» which is mostly similar to Blender’s bone heads. But when you import a Collada file then the bone ends are not defined. This does not matter for connected bones where the bone parent only has one child. In that case the parent bone’s end location is adjusted to the child’s joint position. But especially for unconnected bones and for bones with more than one child we get an issue.

When the Fix Leaf Bones option is enabled then Blender tries to guess where the bone end of unconnected bones would best be placed. If the option is disabled, then the bone ends are placed at an offset along the Y axis. That is why bones often point towards the Y axis.

Find Bone Chains

When a bone has multiple children, then it is not defined which (if any) of the children should be connected to the bone. When the Find Bone Chains option is enabled, then Blender determines the longest bone chain (of children) for each bone. All bones along this chain will then be auto connected.

If the option is disabled, then children will only be connected to parents, if the parent has only one child. But see the Auto Connect option below.

Auto Connect
When this option is enabled, then children will automatically be connected to their parents, if the parent has only one child.
Keep Bind Info

When this option is enabled, then the importer creates two custom properties for each bone:

  • rest_mat – an array of 16 floats which represent the bone’s original rest-pose matrix.
  • bind_mat – an array of 16 floats which represent the bone’s original bind-pose matrix.

Those two arrays can later be used when you want to export the rig again and be sure the original rest pose/bind pose combination must be used.

Technical Details

Mesh

Import

Supported geometry types are:

  • Tris (not tested)
  • Polylist
  • Polygons
  • N-gons
  • Tri-fans (not tested)
  • Lines

Export

Mesh data is exported as <polylist>, <lines> and <vertices>.

Light

Import

Blender does a best effort on importing lights from a .dae. If a Blender profile is detected for lights, all values from these will be used instead. This ensures full re-import from a Blender exported .dae. <extra> support has been added in Blender 2.57.

Export

A Blender profile for lights has been added through the <extra> tag. The entire Light struct from Blender will be exported through this profile, with the exception of light curve falloff.

Material & Effect

Export

Since Blender 2.57 some changes to export of effects have been made. Most notably <lambert> is exported if and only if specularity is 0.

Animation

Export & Import

  • Support for object (mesh, camera, light) transform animations. Only Euler rotations, which is the default option for Objects, can be exported for now. For armature bone animations Euler and quaternion rotation types are supported.
  • Import and export of animations for the following parameters are supported:
    • Light
    • Camera
    • Material effects
  • Non-skin controlling armature bone animation.
  • Animations of armatures with skin deforming bones.
  • Animations of armatures in Object mode.
  • Fully rigified Armature animations (referring to the Rigify add-on). For export of rigified Armature animations:
    • Select Bake Action. (Press Spacebar in 3D View and type «Bake Action».)
    • If you have only the deform bones selected check Only Selected. This will give smaller dae. Otherwise uncheck Only Selected.
    • Check Clear Constraints.
    • Bake Action.
    • Select the mesh and the deform bones. Then export to Collada while checking only selected option. (Selecting only the Mesh and bones is not strictly necessary. Selecting and export only selected will give smaller dae.)
    • Demonstration video

Nodes

On import parent transformations for <instance_node>s is properly propagated to child node instances. Blender materials are exported with the following mapping:

  • Phong
  • Blinn
  • Lambert

For bone nodes which are leaf nodes in the armature tree, or if a bone has more than one children a Blender profile for tip with an <extra> tag, is added for those joint nodes. To correctly derive the bone-to-tail location on re-import.

Nota

Important Things to Remember

  • Object and data-block names are constrained to 21 characters (bytes).
  • UV layer names are constrained to 32 characters (bytes).
  • Only armature animation on mesh, single skin controller.
  • No support for modifiers yet.

When importing a .dae that has <instance_node> on exporting this information is essentially lost and these nodes will be <node>s.