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init(mass:stiffness:damping:initialVelocity:)

Creates a timing parameters object with the specified spring stiffness, mass, damping coefficient, and initial velocity.

Declaration

init(mass: CGFloat, stiffness: CGFloat, damping: CGFloat, initialVelocity velocity: CGVector)

Parameters

  • mass:

    The effective mass of the animated property. This value must be greater than 0.

  • stiffness:

    The spring stiffness coefficient. Higher values correspond to a stiffer spring that yields a greater amount of force for moving objects.

  • damping:

    The damping force to apply to the spring’s motion. This value is used to compute the damping ratio.

  • velocity:

    The target property’s initial rate of change at the start of the spring animation. If the target property doesn’t change, specify a vector with dx and dy components of 0.

    For details about how to calculate this velocity, see Initialvelocity.

Return Value

An initialized spring timing parameters object or nil if the object could not be created.

Discussion

The damping ratio for the spring is computed from the formula damping / (2 * sqrt (stiffness * mass)).

See Also

Initializing a spring timing parameters object