You can also select a character’s action source in the explorer before choosing the Make Skill command so that the source is automatically selected in this Source list.
Preparing the Character’s Animation for Behavior
After you have animated a character, you need to use its action sources to drive the actor’s motion in the Behavior simulation. The character’s action sources need to be converted into skills so that Behavior understands how to use them. For example, a walk cycle action source can be used as the basis for a locomotion skill that determines how the actor will walk in the Behavior simulation.
The skills you need for an actor depend on the content you’re creating in Behavior. For example, with a flocking crowd scene, you might need 5 to 10 different walk or run cycles (locomotion) and a few gestural skills (basic). The behaviors you create using these skills could then randomly select the locomotion cycles to apply to each instance of the actor, or change cycles for each instance of the actor during the simulation. You could also overlay the basic skills on top of the locomotion skills for more interesting movements.
You can make skills for Behavior out of any type of action sources, such as fcurves, constraints, expressions, and cached simulation data (such as the motion from a spring operator). As well, you can define any action source to be loopable, meaning that you can use it as a locomotion skill in Behavior.
You must remove all animation from the character itself before you can create skills from its action sources. You can easily remove animation from a character when you store its animation in action sources, or remove the animation later using the Remove Animation commands from the Animation menu at the bottom of the Softimage window.
For information about storing animation in action sources, see Actions [ Nonlinear Animation ].
Converting an Action into a Skill
After you have initialized a character, you can make skills out of any of its action sources. When you convert an action source to a skill, the action sources are tagged with information; for example, with a locomotion skill, contact keyframes are tagged to mark where the feet of the actor will come into contact with the ground during a locomotion cycle in Behavior.
For characters that are not yet Behavior-ready, choosing the Make Skill command simply tags the source as a Behavior skill type. Then when the Behavior actor is generated from the character, the action source is converted into a Behavior skill.
For Behavior-ready actors, the Make Skill command processes the action source and converts it into a form that runs in Behavior.
To convert an actor’s action sources into a skill
1. Make sure that all animation is removed from the character itself.
2. Make sure that the character is initialized (see Initializing the Character).
3. Select the character whose action source you want to convert to a skill and choose Action > Make Skill from the Behavior Export toolbar.
4. In the Make Skill dialog box that appears, open the Source list and select the action source you want to convert.
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You can also select a character’s action source in the explorer before choosing the Make Skill command so that the source is automatically selected in this Source list. |
5. Select Transfer if you want to transfer the skill you’re creating to a Behavior-ready actor. The actor can be one generated from this character, but it could also be another actor.
The topologies of this character and the target actor don’t have to be the same to transfer the skill. This allows you to create animation on a Softimage character, and then map it onto any Behavior actor.
When you click OK in this dialog box, a pick session starts and you must left or middle-click the actor to which you want to transfer the skill.
6. From the Skill list, select one of the four types of Behavior skills:
- Default - untouched motion data is animation that is not modified for playback in Behavior.
- Basic is ambient animation (that is, no locomotion), such as picking up a ball, throwing a ball, or scratching a head. Basic skills are modified to allow Behavior to easily sequence the skill playback on an actor.
- Locomotion is cycled animation for locomotion inside Behavior. It moves the actor with special marking data used to identify the contact points, such as when the feet contact the floor. The translation animation for the locomotion must be in the actor’s GlobalSRT or COG node.
Locomotion skills are modified so that they can be easily applied for the purpose of actors following paths in Behavior, such as by reorienting the GlobalSRT node in the positive Z direction to match what happens in Behavior.
- Raw is an untouched motion data that is available to be used in Behavior. This option is used for when there is an animation for the actor that needs to be left untouched during the process of converting an action to a skill.
You would probably only need to use this option if you create an action source on a character (usually a terrain actor) with animation that has to show up in Behavior exactly as it is in Softimage.
7. If you’re creating a Locomotion type skill, enter a Threshold value to help detect foot contact with a collision surface.
Lower values make the detection of contact “tighter”, meaning that the foot needs to be in a closer range of the collision surface to be detected; higher values makes the detection “looser”, meaning that the foot can be farther away from the collision surface.
8. Click OK to convert the action source to a skill.
If you selected Transfer, a pick session starts and you must left or middle-click the actor to which you want to transfer the skill.
Making a Cycled (Loopable) Skill
To use an action source as a locomotion skill in Behavior, it needs to be cycled (loopable). Some obvious animation candidates for loopable skills are walk and run cycles, but you can loop any animation you like.
Before you make the action source a loopable skill, make sure that the character’s poses at the start and end frames of the cycle are reasonably close to each other in space.
To make an action loopable
1. Make sure that all animation is removed from the character itself.
2. Make sure that the character is initialized (see Initializing the Character).
3. Select the character whose skill you want to be loopable and choose Action > Make Loop from the Behavior Export toolbar.
4. In the property editor that appears, open the Source list and select the action source you want to make into a loopable skill.
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You can also select a character’s action source in the explorer before choosing the Make Loop command so that the source is automatically selected in this Source list. |
5. Set the Start and End values for the frames of animation that you want to include in the action cycle (loop).
Make sure that frames you include in the cycle are appropriate for a loopable (cyclable) action. The start frame should have enough pre-roll to allow for a good loop to be made.
6. To make a smooth cycle transition, you can select Smooth and set the number of frames used to smooth the end of the cycle to have the first and last keyframes match (except for the translation of a locomotion skill).
A good rule of thumb for this value is a quarter of the difference between the Start and End frames.
7. Select Loco if the skill you’re looping is a locomotion skill. This makes the skill loopable without affecting the forward translation of the actor. For example, if your actor is moving forward in the walk cycle, the actor will walk forward and progress with each cycle.
If you don’t select Loco and the skill is a locomotion, the forward translation portion is made loopable as well so that the actor would walk forward, then slide back to the starting position at the beginning of each loop.
8. Click the Process button to make the action source into a loopable skill with the options you’ve set.
Autodesk Softimage v.7.5