QuickTime 4 Reference

Path Tweener Components

A path tweener component returns a point along a path depending on the current time value. The point is either returned as a FixedPoint value or a MatrixRecord with x and y offsets corresponding to the point. There are six component subtypes:

Subtype kTweenTypePathToFixedPoint returns a tweenResult of type FixedPoint.
Subtype kTweenTypePathToMatrixTranslation returns a tweenResult of type MatrixRecord and performs translation tweening.
Subtype kTweenTypePathToMatrixRotation returns a tweenResult of type MatrixRecord and performs rotation tweening.
Subtype kTweenTypePathToMatrixTranslationAndRotation returns a tweenResult of type MatrixRecord and performs both translation and rotation tweening.
Subtype kTweenTypePathXtoY returns a tweenResult of type FixedPoint that specifies the y-coordinate value for a given x-coordinate value.
Subtype kTweenTypePathYtoX returns a tweenResult of type FixedPoint that specifies the x-coordinate value for a given y-coordinate value.

An example of using a path tweener would be to store a path that you want a sprite to follow. The MatrixRecord returned could be used to determine the offset of the sprite.

The path tweener's path format is the one used by the QuickTime vector codec. A transcoder exists that converts a QuickDraw GX shape into this format.

This component uses only the first contour of the first path in the vector data when determining the output. It ignores any additional atoms and paths in the vector data.

Note
If the kTweenReturnDelta flag (in an optional kTweenFlags atom) is set, the component returns the change in value from the last time it was invoked. If the flag is not set, or if the component has not previously been invoked, the component returns the normal result for the tween.