Try It! Animating a Shape

Animated shapes add realism to a scene: you can watch the throat of a frog expand and contract as he breathes, and you can see a bouncing rubber ball flatten slightly when it hits the ground. The technique for animating a shape is similar to the technique for animating the movements of an object: you move the time marker in the keyframe animator to the appropriate time, change the points, edges, or polygons of a PEP object, and then record the keyframe.

Click here to preview an animation similar to the one you're about to create.

If a PEP object has a shape animation associated with it, you won't be able to use any of the PEP editing tools to split polygons or delete polygons from the shape. If you try to alter the number of points in an animated shape, the following message appears:

Be sure to make all changes to the topology of your shape before you begin recording the animation.

Reminder: Use Edit > Undo (Ctrl + Z) and Edit > Redo (Shift + Ctrl + Z) in the main window to undo and redo changes made in the Keyframe Animator as well as changes made in the main window. The Keyframe Animator uses the same undo buffer as the main application.

Animating a Simple Shape

Follow these steps to set up the animation:

  1. In Cosmo Worlds, open the sample file /usr/share/Insight/library/SGI_bookshelves/Help/books/CosmoWorlds_UG/Models/frog.wrl

    If you were going to edit a primitive object such as a sphere, you'd need to click the Convert to PEP Object button:

    The frog is already a PEP object, so the PEP hammer is grayed out.

  2. Click the PEP Editor button:


    A dialog box appears asking you to select a child. Dismiss the box and then click the Select Child down arrow to select the bottom half of the frog's body. Click the PEP Editor button; an orange box appears to indicate PEP editing mode.

  3. Start the Keyframe Animator by clicking its button:

  4. Choose Animation > New animation. Then choose Animation > Change name and type in a name for your animation: myfrog.

  5. Add the frog as a member of the animation by choosing Animation > Add member.

  6. Choose Animation > Set duration and set the duration to 10 frames.

Now you're ready to animate the shape:

  1. Move the current time marker (the red triangle) in the Keyframe Animator to frame 5.

  2. In the main window, Shift-click to select the polygons that form the throat of the frog, as shown in the figure below.



  3. Click-drag the selection to expand the frog's throat. (To get a better angle, hold down the Alt key to switch temporarily to the Examiner Viewer so that you can rotate the frog.)

    If you press the Ctrl key when you click-drag, you can pull out the vertices in a direction perpendicular to the surface of the frog's throat.

  4. In the Keyframe Animator, click the master Record button to record the keyframe.

  5. Move the current time marker to frame 10.

  6. In the main window, click-drag the frog's throat to its original position (or simply copy and paste the keys from frame 0 to frame 10).

  7. Click the master Record button to record the keyframe.

  8. In the Keyframe Animator, click the Play arrow to preview the animation.

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