backend/libs/three/math/interpolants/QuaternionLinearInterpolant.js

import { Interpolant } from '../Interpolant.js';
import { Quaternion } from '../Quaternion.js';

/**
 * Spherical linear unit quaternion interpolant.
 */

class QuaternionLinearInterpolant extends Interpolant {
	constructor(parameterPositions, sampleValues, sampleSize, resultBuffer) {
		super(parameterPositions, sampleValues, sampleSize, resultBuffer);
	}

	interpolate_(i1, t0, t, t1) {
		const result = this.resultBuffer,
			values = this.sampleValues,
			stride = this.valueSize,
			alpha = (t - t0) / (t1 - t0);

		let offset = i1 * stride;

		for (let end = offset + stride; offset !== end; offset += 4) {
			Quaternion.slerpFlat(result, 0, values, offset - stride, values, offset, alpha);
		}

		return result;
	}
}

export { QuaternionLinearInterpolant };