Mecanim

Mecanim is Unity’s animation system, introduced with Unity 4, designed to provide advanced authoring, blending, and retargeting for character animations. It offers a unified workflow for both humanoid and non-humanoid characters, enabling more natural and interactive motion in games and simulations.

The system centers on three key concepts: the Animator component, the Animator Controller, and the Avatar. The Animator component runs on a character and drives its animations. The Animator Controller is a asset that encodes a graph of states and transitions that determine which animation clip plays and when. The Avatar defines the mapping from a character’s skeleton to a standard humanoid rig, enabling retargeting of animations between different characters that share the Humanoid avatar.

Core features include a state-machine based workflow with parameters that drive transitions between animation states, and blend trees that smoothly interpolate between multiple clips. Mecanim supports multiple layers and avatar masks, allowing simultaneous animation of different body parts (for example, upper body and lower body) or selective animation control. Root motion can be enabled to extract movement from animation data, and inverse kinematics (IK) can be implemented via scripting with OnAnimatorIK to adjust limb positioning in real time. Mecanim also supports animation events, retargeting across characters using a Humanoid avatar, and integration with the Unity animation pipeline.

Workflow typically involves importing animation clips, configuring rigs as Humanoid or Generic, creating an Animator Controller, adding states linked to clips, and defining transitions with conditions. Developers can control animation parameters at runtime through the Animator API to drive complex, responsive character motion.