keyframeTrack.getInterpolation()

The keyframeTrack.getInterpolation() method is a built-in function in the Three.js library that allows for interpolation between two keyframe values.

Syntax

keyframeTrack.getInterpolation( index )

Parameters

• index - An integer representing the index of the keyframe for which interpolation is to be computed.

Return Value

The method returns an object containing the following properties:

• start - The index of the starting keyframe that was used for interpolation.
• end - The index of the ending keyframe that was used for interpolation.
• factor - A value between 0 and 1 representing the percentage of interpolation between the starting and ending keyframes.

Description

The keyframeTrack.getInterpolation() method is typically used in performance animation and timing functions in the Three.js library. This method allows smooth transitions between two keyframes, providing a more realistic and dynamic look to animated sequences.

This method works by analyzing the sequence of keyframes in the track, including their positions, rotations, and scales, to compute the specific interpolation for a given index. This interpolation factor is then used in conjunction with the keyframes to provide a seamless transition between them.

Examples

Here is an example of how to use keyframeTrack.getInterpolation() in Three.js:

const clip = THREE.AnimationClip.findByName( gltf.animations, 'walk' );
const mixer = new THREE.AnimationMixer( gltf.scene );

const action = mixer.clipAction( clip );
action.play();

// In the animation loop
const time = Date.now() * 0.001;

// Set the time of the mixer
mixer.setTime( time );

// Get interpolation for a specific keyframe index
const index = 2;
const interp = action.getClip().tracks[0].getInterpolation( index );

// Do something with the interpolation (e.g. change a material color)
const color = new THREE.Color( 0xff0000 );
color.lerp( new THREE.Color( 0x00ff00 ), interp.factor );
mesh.material.color = color;

In this example, we are using keyframeTrack.getInterpolation() to obtain the interpolation value for the third keyframe on the first track of the animation clip. We then use this interpolation factor to change the color of a mesh over time, giving the appearance of a smooth color transition.

Conclusion

The keyframeTrack.getInterpolation() method is a powerful tool for enhancing animations in Three.js. With it, you can create smooth transitions between two keyframes and achieve a more natural, dynamic look to your animated sequences.