Actor Basics

Actors for animation sequences are created as special cells from one or more elements in a design. Once created, actors must be “instructed” where and when to move. This is done by scripting each actor using keyframes, defining a path, or by applying a parametric motion formula. Using the latter technique, you can script the position, rotation, or scale of an actor as a function of time, or frame number.

It is not necessary to create actors for keyframe animation. Where hierarchical motion is required, however, it is often convenient to define actors and their hierarchical relationships. This simplifies the positioning of assemblies for keyframing.

Actors, with names, are required for defining actor paths or parametric motion control. These tools detect and refer to elements in the design by actor name only.

In general, it is recommended that actor names be unique, but it can be desirable to have actors with the same name when you want to apply the same scripted motion to them.

Working with actors

Tools for creating and manipulating actors are contained in the Animation Actors tool box.

The Tool Settings window for those tools that operate on existing actors can optionally display a list box with the names of the actors. Hierarchical actor relationships (see Hierarchical motion) are indicated with indentation and color-coding:

Black indicates the actor is neither attached to other actors, nor has actors attached to it.
Red indicates the actor is a “parent” — it has an actor(s) attached to it — its “child” — at a lower level in the hierarchy.
Blue indicates the actor is a “child” — it is attached to another actor — its “parent” — at a higher level in the hierarchy.

Selecting an actor in the list box, by clicking its name, highlights the actor in the view window. Double-clicking an actor name identifies the actor to be operated upon by the selected tool. It is also possible to graphically identify an actor rather than using the Tool Settings window.

If there are multiple actors with the same name and the same object highlights regardless of which list box entry with that name is selected, drop each actor with the Drop Actor tool and recreate them with the Create Actor tool. This should be necessary only for actors created with early pre-release versions of the MicroStation Version 1.0 Animation Producer.

Range of motion

Ways in which an actor can move, parametrically, in an animation are defined at the time of the actor's creation. Controls for specifying an actor's manipulation are in the Create Actor tool settings window. Initial movement, rotation, and scaling, can be relative to the Design, View, or an ACS axis system — chosen from the Orientation options menu. The actor is confined to movement, rotation, and scaling about the chosen axes.

When defining an actor's movement options, an “animation” coordinate system is created. As the actor is manipulated, either with the Manipulate Actor tool , or during an animation, the defined axis system moves and rotates with the actor. That is, it remains constant relative to the actor.

After an actor has been defined, you can change its manipulation options with the Modify Actor tool.

Hierarchical motion

Using the Attach Actor tool, you can specify that particular actors are attached to each other as an assembly of parts. Attachment is performed in a hierarchical manner, such that moving an actor also moves any actors below it in the hierarchy. This is most useful for positioning actors for keyframing.

Take, as an example, a model of a human body. To create a hierarchical assembly of a leg you would start at the foot, and finish at the thigh. In this example:

Moving the thigh moves the calf and foot also, because they are lower in the hierarchy.
Similarly, moving the calf also moves the foot (but not the thigh).
Moving the foot would not move the calf or thigh.


Manipulating the upper leg takes with it those parts lower in the hierarchy (the calf and foot).


Manipulating the calf takes only the foot with it. Only the foot is lower in the hierarchy.


Manipulating the foot moves nothing else, because the foot is the lowest element of the hierarchy.

Hierarchical motion simplifies the task of moving actors to their required position for each keyframe. As with standard actors, when the animation is being recorded, the intervening frames are interpolated from the keyframes.

General Procedure — To define hierarchical motion

Create the actors with the Create Actor tool.

(Optional, desirable) Using the Manipulate Actor tool, test each actor's range of motion.

Using the Attach Actor tool, attach the actors to each other, starting with the lowest in the hierarchy through to the top.

Using the Manipulate Actor tool, move the actors to their required locations.

If an animation includes many actors that move independently of one another, then separate keyframes can be created for each actor. They then can be scripted separately, thus simplifying an otherwise complex task.