Beyond Basic VRML Animation: Keyframe Animation and Interpolation
By Andrea L. Ames
In last month's discussion of VRML animation basics, I pointed out that the data types of the sender node's output and the receiver node's input must be the same. However, this rule makes for some pretty boring worlds. You want shapes to walk, fly, or dance across your virtual scenes. But how do you specify that a new time of type SFFloat should cause a shape to move to a new position of type SFVec3f or to a new orientation of type SFRotation? You need a way to convert between VRML data types.
VRML's interpolator nodes may be just what you need; they are akin to the conversion factors you used in high-school math and science to convert between the English and metric systems of measurement. The PositionInterpolatorTimeSensorTranslation node. The Translation node can then take that position as input, changing the position of its coordinate system and all the shapes within it.
This month, I'll describe how you can use interpolators to create more interesting animation. I'll also discuss keyframe animation, which allows you to specify a few places (or "key values") along the general path you want shapes to follow during animation and let the viewer's browser fill in the gaps.<>
