IUIAnimationInterpolator::InterpolateVelocity method (uianimation.h)

Interpolates the velocity, or rate of change, at the specified offset.

Syntax

HRESULT InterpolateVelocity(
  [in]  UI_ANIMATION_SECONDS offset,
  [out] DOUBLE               *velocity
);

Parameters

[in] offset

The offset from the start of the transition.

The offset is always greater than or equal to zero and less than or equal to the duration of the transition. This method is not called if the duration of the transition is zero.

[out] velocity

The interpolated velocity.

Return value

If the method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code. See Windows Animation Error Codes for a list of error codes.

Remarks

Windows Animation always calls the SetInitialValueAndVelocity method to set the initial value and velocity before calling InterpolateVelocity, so a custom interpolator need not check whether the initial value and velocity have been set.

Windows Animation can call SetInitialValueAndVelocity multiple times with different parameters. Interpolators can cache internal state to improve performance, but they must update this cached state each time SetInitialValueAndVelocity is called and ensure that the results of subsequent calls to InterpolateVelocity reflect the updated state.

Requirements

See also

IUIAnimationInterpolator

UI_ANIMATION_SECONDS