The Global Motion Clip and Master Motion Clip controllers are used to create animation for multiple objects. Groups of creatures such as birds, butterflies, schools of fish and bugs can be animated using these tools. You can create clip controllers either as block controllers in Track View or more directly in the Crowd helper controls on the Global Clip Controllers rollout. Clip controllers are generally used to animate non-biped creatures.
You can animate your creature either in place with looping animation but no transformational motion (such as a bird flapping its wings), or you can incorporate transformational motion into the animation as well (the bird moves upward while flapping its wings). In-place cyclic motion lends itself to flying or swimming motions like birds and fish, while adding lateral motion lends itself to crawling type animation where feet should be planted on the ground and not sliding. Depending on which you use, you toggle options on the Motion Clips tab of the Synthesis dialog. In both cases, you use crowd delegates driven by behaviors to motivate the creatures, which are linked to those delegates.
First you create a creature with a few short loop cycles, like the beating of wings, gliding, turning left and turning right. This creature is assigned as the Global Object or the master object from which the motion clips will be derived. Then clones of the original creature are created. The clones are positioned and linked to delegates. States are created to select which clips will play based on a state.
For example, if a bird (delegate) is pitching up or accelerating, the fast-beating clip is used; if the bird (delegate) slows to a stop, the wings-at-rest clip is used, and so on. During synthesis, the software determines which state should be active depending on the speed and direction of the delegates. An active state determines which clip should be applied to the clones of the original object. Clips are blended together to create the animation. Available states are speed, acceleration, pitch, pitch velocity, heading velocity, or script (MAXScript).
The Using Crowd with Animated Non-Biped Objects tutorial covers this method.
For multi-legged creatures that walk, you can animate lateral motion as well as the cyclic motion of the legs moving. This is done to ensure that the creatures' feet do not slide as it moves. The software then uses the lateral motion information to create a state that perfectly matches the actual motion. The software then strips the actual motion out. When a delegate approaches the speed and heading recorded in that state, the appropriate motion clip is triggered. This technique minimizes sliding feet.
Use the character studio crowd tools to create the initial motion for the delegates. Use a seek or avoid behavior to steer birds, for example. Your object with the loop animation is then copied and the copies are linked to the delegates to create the complete animation. The delegate handles the path and the clip controllers handle the looped animation.
You can create Master Motion Clip and Global Motion Clip by going into Track View and assigning a controller to the available controller under Block Control. It is, however, simpler to use the user interface in the Crowd helper controls on the Global Clip Controller rollout to apply and use these clip controllers.
Clip State Dialog
Global Motion Clips store the clips to be shared among multiple MasterMotionClips. GlobalMotionClips also contain the logic for performing motion synthesis on a collection of objects with trajectories and states associated with clips. Controls for motion synthesis are in the Synthesis dialog.
The way the motionclip keys are scaled and ordered depends upon user-defined states. Each state contains one or more motionclips that will be played when the state is active.
MasterMotionClips are controllers that contain motionclips or individual clips of animation. These motionclips are combined end to end to create animation. Motion clips that overlap are blended to smooth the transitions between clips.
All of the work involved in copying and synthesizing clips takes place using controls in the Synthesis Dialog.
Steps to synthesize objects
First, a global object is selected that subsequent motionclips will be created from. Think of the global object as a template that is used to create the motionclip animations, but itself is never synthesized.
A motionclip is a subset of an object's animation. For example, flapping and gliding motion in the objects animation yields two motionclips.
From this global object, animations are created and stored as motionclips.
You can animate the character in place or with lateral movement, the software can handle both cases. A bird can have a flap animation, a dive animation, and a land animation, which when blended, scaled, and combined can create effective-looking animations for a large number of creatures.
Create states are created that specify when a particular motionclip is active. For example, a flap motionclip is active if the acceleration of the bird (delegate) is greater than zero, while a glide motionclip is active if the acceleration is less than zero.
Objects to be synthesized will probably be clones of the global object and need to contain the same node and controller hierarchy. Otherwise they can be different in other ways; for example, they may be scaled, textured or skinned differently.
For each object selected to be synthesized, an associated MasterMotionClip controller is created under the GlobalMotionClip in Track View. It is here that the synthesis algorithm places the keys.
You also need to specify where the blending between two motionclips occurs. You can do this automatically by letting the computer analyze the motionclips and find a transition point that minimizes error, or you can manually specify the frame number at which the blend should start.
Synthesis for the selected objects occurs based upon which states are active, the available motionclips under each state, and the specified transition points.
You can also hand modify the resulting animation by manipulating the keys inside Track View, or by collapsing the keys completely (Collapse Selected on the Synthesis tab) and then hand modifying the resulting animation in the scene.