C3D is a binary format which stores animated 3D point data. Using Motion Builder, we can convert this point data to a format (BVH, in this case) which can be used to animate a digital character rigged with a skeleton. This process imports a set of C3D data into Motion Builder and then configures a biped character to fit this data.
(hierarchy of rotation data)
To get started, add the path to your folder where the C3D data is stored in the AssetBrowser (with the second mouse button click in the navigator and choose the add favorite path option).
You can now import the rest of the C3D files. Each will go into its own take. Drag and drop the C3D file and select Import Options. From this dialog, select Merge and import the start/end from the file.
Mapping motions to a joint hierarchy
You can now import a model that is driven by this model. Drag and drop the model from the asset browser into the work view window and choose the merge option, with no animation. For example, import a biped bone_skeleton from the tutorial assets with merge, no animation.
Next, add a character to the scene. First, we map the biped bone_skeleton to the character by specifying the biped's joints in the naming template window. As a shortcut, click on the Hip joint in the scene hierarchy, select all branches, and then drag the Hip join onto the hip joint in the naming template (all joints should get extracted).
Now we can link the character's movement to the actor driven by C3D data. Click characterize and then in the character control window, select Actor Input. Specify the actor as the character's input.
The process above also works for skinned models. Any input FBX can be loaded.
Exporting from Motion Builder
After we have mapped the motion to a joint hierarchy, we can export to numerous formats.