Autodesk MotionBuilder is a paid 3D character animation application for Windows and Linux. It turns recorded motion or manually keyed poses into character movement for 3D projects. Its interactive environment combines animation playback, editing and exchange with other 3D software.
Character mapping and characterization
MotionBuilder starts with a character model and its skeleton. A Character asset maps that structure, manually or automatically, into a character definition. Characterizing the model activates the definition so a motion source can drive the character.
The characterization controls distinguish biped and quadruped postures. The model must face the positive Z-axis in its stance. For human movement, the character engine establishes joint relationships, so moving an elbow also affects the connected arm joints.
Recorded motion capture
Recorded marker movement is connected through an Actor asset. Its Marker set maps the captured data, and the Actor is linked to the target character. Adjusting that connection determines how the recording drives the character in the scene.
Plotting transfers the motion onto the character's skeleton. The resulting animation can then play independently of the recorded data and be exported. This separates the capture mapping used to drive the character from the skeleton animation delivered to another application.
Control rigs and pose editing
A Control rig provides position and rotation controls on a characterized character. Moving those controls and setting keyframes creates animation from scratch. Body-part pinning holds selected parts in place, while floor contact keeps the feet from passing through the floor.
Existing skeleton animation is plotted onto the rig for editing. The animator can reduce or exaggerate movement and fill gaps in imported motion. Once those changes are complete, plotting back to the skeleton prepares the animation for export.
Poses can be saved and reused across takes. Character Extensions include extra limbs, wings or tails in those poses. Rig assets also retain settings such as pinning, stiffness, reach and pull for reuse on other characters.
Retargeting character movement
Retargeting uses animation from one character to drive another without first baking either skeleton. MotionBuilder accepts both keyed animation and motion data for this purpose. Character Controls can transfer movement between characters in the scene or use saved takes.
Retarget Rig copies keyframes directly between Control rigs and adjusts for differences in character size. Proper keyframe transfer requires equivalent character setups. Differences in the number of spine bones affect how movement maps between the source and target.
Motion Reduction controls adjust how much movement passes from the source's chest, neck, head and shoulders to the corresponding target parts. These controls change the transferred movement while the target continues to follow the source animation.
Animation curves and timing
The FCurves window exposes animation curves for precise keyframe editing. Timewarp curve points change the pace of an animation, speeding or slowing its movement. These adjustments refine existing motion after capture, retargeting or manual pose animation.
Animation layers
Animation layers hold additional keyframes above the original curves. A new layer can change part of a movement without overwriting those original keys. The stacked layers combine to produce the animation played in the scene.
The layer editor controls order, parenting, weights and whether a layer overrides lower layers. Muting or soloing layers isolates their contributions for comparison. An accepted change can be merged; an unwanted layer can be discarded while retaining the original motion.
Story clips and transitions
The Story window arranges clips representing scene actions on tracks in its Action and Edit timelines. It can work with animation, video and audio. Rearranging the story preserves the original action and does not alter the current take.
Animation, character and camera animation clips on the same track blend by interpolation when they do not overlap. Dragging one over another creates a cross-blend. Fade and Still handles refine that transition; constraint clips also support cross-blending.
Scene files and motion exchange
MotionBuilder imports FBX scenes from other 3D packages and saves its own scenes in FBX. Save controls select which assets, settings and takes to include. Media can be embedded, and individual takes can be saved into separate files.
Motion data can also be imported and exported in several formats:
- ASF and AMC: the ASF file defines the skeleton; AMC files hold its movement.
- BVH: carries hierarchical or skeletal motion data.
- HTR: carries hierarchical transformation and rotation data.
- TRC and C3D: provide motion-data exchange, with C3D used for data from Vicon capture hardware.
Imported meshes support up to eight bone influences per vertex; additional influences produce skinning artifacts. Saved MotionBuilder FBX scenes have a 2 GB limit. Files exceeding that limit cannot be reopened in the application.
Plotted skeleton animation can be passed to other 3D software, including workflows using Maya and 3ds Max. MotionBuilder is available by subscription, with a 30-day free trial providing temporary access to the application.
