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web-app/node_modules/three/examples/jsm/curves/NURBSCurve.js

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+import {
+	Curve,
+	Vector3,
+	Vector4
+} from 'three';
+import * as NURBSUtils from '../curves/NURBSUtils.js';
+
+/**
+ * NURBS curve object
+ *
+ * Derives from Curve, overriding getPoint and getTangent.
+ *
+ * Implementation is based on (x, y [, z=0 [, w=1]]) control points with w=weight.
+ *
+ **/
+
+class NURBSCurve extends Curve {
+
+	constructor(
+		degree,
+		knots /* array of reals */,
+		controlPoints /* array of Vector(2|3|4) */,
+		startKnot /* index in knots */,
+		endKnot /* index in knots */
+	) {
+
+		super();
+
+		const knotsLength = knots ? knots.length - 1 : 0;
+		const pointsLength = controlPoints ? controlPoints.length : 0;
+
+		this.degree = degree;
+		this.knots = knots;
+		this.controlPoints = [];
+		// Used by periodic NURBS to remove hidden spans
+		this.startKnot = startKnot || 0;
+		this.endKnot = endKnot || knotsLength;
+
+		for ( let i = 0; i < pointsLength; ++ i ) {
+
+			// ensure Vector4 for control points
+			const point = controlPoints[ i ];
+			this.controlPoints[ i ] = new Vector4( point.x, point.y, point.z, point.w );
+
+		}
+
+	}
+
+	getPoint( t, optionalTarget = new Vector3() ) {
+
+		const point = optionalTarget;
+
+		const u = this.knots[ this.startKnot ] + t * ( this.knots[ this.endKnot ] - this.knots[ this.startKnot ] ); // linear mapping t->u
+
+		// following results in (wx, wy, wz, w) homogeneous point
+		const hpoint = NURBSUtils.calcBSplinePoint( this.degree, this.knots, this.controlPoints, u );
+
+		if ( hpoint.w !== 1.0 ) {
+
+			// project to 3D space: (wx, wy, wz, w) -> (x, y, z, 1)
+			hpoint.divideScalar( hpoint.w );
+
+		}
+
+		return point.set( hpoint.x, hpoint.y, hpoint.z );
+
+	}
+
+	getTangent( t, optionalTarget = new Vector3() ) {
+
+		const tangent = optionalTarget;
+
+		const u = this.knots[ 0 ] + t * ( this.knots[ this.knots.length - 1 ] - this.knots[ 0 ] );
+		const ders = NURBSUtils.calcNURBSDerivatives( this.degree, this.knots, this.controlPoints, u, 1 );
+		tangent.copy( ders[ 1 ] ).normalize();
+
+		return tangent;
+
+	}
+
+	toJSON() {
+
+		const data = super.toJSON();
+
+		data.degree = this.degree;
+		data.knots = [ ...this.knots ];
+		data.controlPoints = this.controlPoints.map( p => p.toArray() );
+		data.startKnot = this.startKnot;
+		data.endKnot = this.endKnot;
+
+		return data;
+
+	}
+
+	fromJSON( json ) {
+
+		super.fromJSON( json );
+
+		this.degree = json.degree;
+		this.knots = [ ...json.knots ];
+		this.controlPoints = json.controlPoints.map( p => new Vector4( p[ 0 ], p[ 1 ], p[ 2 ], p[ 3 ] ) );
+		this.startKnot = json.startKnot;
+		this.endKnot = json.endKnot;
+
+		return this;
+
+	}
+
+}
+
+export { NURBSCurve };