<!-- SOLUV · part 222 -->
ray} sampleValues - The sample values.
	 * @param {number} sampleSize - The sample size
	 * @param {TypedArray} [resultBuffer] - The result buffer.
	 */
	constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

		super( parameterPositions, sampleValues, sampleSize, resultBuffer );

		this._weightPrev = -0;
		this._offsetPrev = -0;
		this._weightNext = -0;
		this._offsetNext = -0;

		this.DefaultSettings_ = {

			endingStart: ZeroCurvatureEnding,
			endingEnd: ZeroCurvatureEnding

		};

	}

	intervalChanged_( i1, t0, t1 ) {

		const pp = this.parameterPositions;
		let iPrev = i1 - 2,
			iNext = i1 + 1,

			tPrev = pp[ iPrev ],
			tNext = pp[ iNext ];

		if ( tPrev === undefined ) {

			switch ( this.getSettings_().endingStart ) {

				case ZeroSlopeEnding:

					// f'(t0) = 0
					iPrev = i1;
					tPrev = 2 * t0 - t1;

					break;

				case WrapAroundEnding:

					// use the other end of the curve
					iPrev = pp.length - 2;
					tPrev = t0 + pp[ iPrev ] - pp[ iPrev + 1 ];

					break;

				default: // ZeroCurvatureEnding

					// f''(t0) = 0 a.k.a. Natural Spline
					iPrev = i1;
					tPrev = t1;

			}

		}

		if ( tNext === undefined ) {

			switch ( this.getSettings_().endingEnd ) {

				case ZeroSlopeEnding:

					// f'(tN) = 0
					iNext = i1;
					tNext = 2 * t1 - t0;

					break;

				case WrapAroundEnding:

					// use the other end of the curve
					iNext = 1;
					tNext = t1 + pp[ 1 ] - pp[ 0 ];

					break;

				default: // ZeroCurvatureEnding

					// f''(tN) = 0, a.k.a. Natural Spline
					iNext = i1 - 1;
					tNext = t0;

			}

		}

		const halfDt = ( t1 - t0 ) * 0.5,
			stride = this.valueSize;

		this._weightPrev = halfDt / ( t0 - tPrev );
		this._weightNext = halfDt / ( tNext - t1 );
		this._offsetPrev = iPrev * stride;
		this._offsetNext = iNext * stride;

	}

	interpolate_( i1, t0, t, t1 ) {

		const result = this.resultBuffer,
			values = this.sampleValues,
			stride = this.valueSize,

			o1 = i1 * stride,		o0 = o1 - stride,
			oP = this._offsetPrev, 	oN = this._offsetNext,
			wP = this._weightPrev,	wN = this._weightNext,

			p = ( t - t0 ) / ( t1 - t0 ),
			pp = p * p,
			ppp = pp * p;

		// evaluate polynomials

		const sP = - wP * ppp + 2 * wP * pp - wP * p;
		const s0 = ( 1 + wP ) * ppp + ( -1.5 - 2 * wP ) * pp + ( -0.5 + wP ) * p + 1;
		const s1 = ( -1 - wN ) * ppp + ( 1.5 + wN ) * pp + 0.5 * p;
		const sN = wN * ppp - wN * pp;

		// combine data linearly

		for ( let i = 0; i !== stride; ++ i ) {

			result[ i ] =
					sP * values[ oP + i ] +
					s0 * values[ o0 + i ] +
					s1 * values[ o1 + i ] +
					sN * values[ oN + i ];

		}

		return result;

	}

}

/**
 * A basic linear interpolant.
 *
 * @augments Interpolant
 */
class LinearInterpolant extends Interpolant {

	/**
	 * Constructs a new linear interpolant.
	 *
	 * @param {TypedArray} parameterPositions - The parameter positions hold the interpolation factors.
	 * @param {TypedArray} sampleValues - The sample values.
	 * @param {number} sampleSize - The sample size
	 * @param {TypedArray} [resultBuffer] - The result buffer.
	 */
	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,

			offset1 = i1 * stride,
			offset0 = offset1 - stride,

			weight1 = ( t - t0 ) / ( t1 - t0 ),
			weight0 = 1 - weight1;

		for ( let i = 0; i !== stride; ++ i ) {

			result[ i ] =
					values[ offset0 + i ] * weight0 +
					values[ offset1 + i ] * weight1;

		}

		return result;

	}

}

/**
 * Interpolant that evaluates to the sample value at the position preceding
 * the parameter.
 *
 * @augments Interpolant
 */
class DiscreteInterpolant extends Interpolant {

	/**
	 * Constructs a new discrete interpolant.
	 *
	 * @param {TypedArray} parameterPositions - The parameter positions hold the interpolation factors.
	 * @param {TypedArray} sampleValues - The sample values.
	 * @param {number} sampleSize - The sample size
	 * @param {TypedArray} [resultBuffer] - The result buffer.
	 */
	constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

		super( parameterPositions, sampleValues, sampleSize, resultBuffer );

	}

	interpolate_( i1 /*, t0, t, t1 */ ) {

		return this.copySampleValue_( i1 - 1 );

	}

}

/**
 * A Bezier interpolant using cubic Bezier curves with 2D control points.
 *
 * This interpolant supports the COLLADA/Maya style of Bezier animation where
 * each keyframe has explicit in/out tangent control points specified as
 * 2D coordinates (time, value).
 *
 * Tangent data is read from `inTangents` and `outTangents` on the interpolant
 * (populated by `KeyframeTrack.InterpolantFactoryMethodBezier`).
 *
 * For a track with N keyframes and stride S:
 * - Each tangent array has N * S * 2 values
 * - Layout: [k0_c0_time, k0_c0_value, k0_c1_time, k0_c