<!-- AVATAR-FORGE · part 222 -->
valChanged_( 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;

	}

}

class LinearInterpolant 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,

			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.
 */

class DiscreteInterpolant extends Interpolant {

	constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

		super( parameterPositions, sampleValues, sampleSize, resultBuffer );

	}

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

		return this.copySampleValue_( i1 - 1 );

	}

}

class KeyframeTrack {

	constructor( name, times, values, interpolation ) {

		if ( name === undefined ) throw new Error( 'THREE.KeyframeTrack: track name is undefined' );
		if ( times === undefined || times.length === 0 ) throw new Error( 'THREE.KeyframeTrack: no keyframes in track named ' + name );

		this.name = name;

		this.times = convertArray( times, this.TimeBufferType );
		this.values = convertArray( values, this.ValueBufferType );

		this.setInterpolation( interpolation || this.DefaultInterpolation );

	}

	// Serialization (in static context, because of constructor invocation
	// and automatic invocation of .toJSON):

	static toJSON( track ) {

		const trackType = track.constructor;

		let json;

		// derived classes can define a static toJSON method
		if ( trackType.toJSON !== this.toJSON ) {

			json = trackType.toJSON( track );

		} else {

			// by default, we assume the data can be serialized as-is
			json = {

				'name': track.name,
				'times': convertArray( track.times, Array ),
				'values': convertArray( track.values, Array )

			};

			const interpolation = track.getInterpolation();

			if ( interpolation !== track.DefaultInterpolation ) {

				json.interpolation = interpolation;

			}

		}

		json.type = track.ValueTypeName; // mandatory

		return json;

	}

	InterpolantFactoryMethodDiscrete( result ) {

		return new DiscreteInterpolant( this.times, this.values, this.getValueSize(), result );

	}

	InterpolantFactoryMethodLinear( result ) {

		return new LinearInterpolant( this.times, this.values, this.getValueSize(), result );

	}

	InterpolantFactoryMethodSmooth( result ) {

		return new CubicInterpolant( this.times, this.values, this.getValueSize(), result );

	}

	setInterpolation( interpolation ) {

		let factoryMethod;

		switch ( interpolation ) {