156 lines
3.8 KiB
JavaScript
156 lines
3.8 KiB
JavaScript
import {
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Curve,
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Vector3,
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Vector4
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} from 'three';
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import * as NURBSUtils from '../curves/NURBSUtils.js';
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/**
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* This class represents a NURBS curve.
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*
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* Implementation is based on `(x, y [, z=0 [, w=1]])` control points with `w=weight`.
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*
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* @augments Curve
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* @three_import import { NURBSCurve } from 'three/addons/curves/NURBSCurve.js';
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*/
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class NURBSCurve extends Curve {
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/**
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* Constructs a new NURBS curve.
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*
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* @param {number} degree - The NURBS degree.
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* @param {Array<number>} knots - The knots as a flat array of numbers.
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* @param {Array<Vector2|Vector3|Vector4>} controlPoints - An array holding control points.
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* @param {number} [startKnot] - Index of the start knot into the `knots` array.
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* @param {number} [endKnot] - Index of the end knot into the `knots` array.
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*/
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constructor( degree, knots, controlPoints, startKnot, endKnot ) {
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super();
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const knotsLength = knots ? knots.length - 1 : 0;
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const pointsLength = controlPoints ? controlPoints.length : 0;
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/**
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* The NURBS degree.
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*
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* @type {number}
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*/
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this.degree = degree;
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/**
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* The knots as a flat array of numbers.
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*
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* @type {Array<number>}
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*/
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this.knots = knots;
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/**
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* An array of control points.
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*
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* @type {Array<Vector4>}
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*/
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this.controlPoints = [];
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/**
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* Index of the start knot into the `knots` array.
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*
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* @type {number}
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*/
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this.startKnot = startKnot || 0;
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/**
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* Index of the end knot into the `knots` array.
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*
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* @type {number}
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*/
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this.endKnot = endKnot || knotsLength;
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for ( let i = 0; i < pointsLength; ++ i ) {
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// ensure Vector4 for control points
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const point = controlPoints[ i ];
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this.controlPoints[ i ] = new Vector4( point.x, point.y, point.z, point.w );
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}
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}
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/**
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* This method returns a vector in 3D space for the given interpolation factor.
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*
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* @param {number} t - A interpolation factor representing a position on the curve. Must be in the range `[0,1]`.
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* @param {Vector3} [optionalTarget] - The optional target vector the result is written to.
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* @return {Vector3} The position on the curve.
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*/
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getPoint( t, optionalTarget = new Vector3() ) {
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const point = optionalTarget;
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const u = this.knots[ this.startKnot ] + t * ( this.knots[ this.endKnot ] - this.knots[ this.startKnot ] ); // linear mapping t->u
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// following results in (wx, wy, wz, w) homogeneous point
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const hpoint = NURBSUtils.calcBSplinePoint( this.degree, this.knots, this.controlPoints, u );
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if ( hpoint.w !== 1.0 ) {
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// project to 3D space: (wx, wy, wz, w) -> (x, y, z, 1)
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hpoint.divideScalar( hpoint.w );
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}
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return point.set( hpoint.x, hpoint.y, hpoint.z );
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}
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/**
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* Returns a unit vector tangent for the given interpolation factor.
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*
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* @param {number} t - The interpolation factor.
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* @param {Vector3} [optionalTarget] - The optional target vector the result is written to.
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* @return {Vector3} The tangent vector.
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*/
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getTangent( t, optionalTarget = new Vector3() ) {
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const tangent = optionalTarget;
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const u = this.knots[ 0 ] + t * ( this.knots[ this.knots.length - 1 ] - this.knots[ 0 ] );
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const ders = NURBSUtils.calcNURBSDerivatives( this.degree, this.knots, this.controlPoints, u, 1 );
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tangent.copy( ders[ 1 ] ).normalize();
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return tangent;
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}
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toJSON() {
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const data = super.toJSON();
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data.degree = this.degree;
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data.knots = [ ...this.knots ];
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data.controlPoints = this.controlPoints.map( p => p.toArray() );
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data.startKnot = this.startKnot;
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data.endKnot = this.endKnot;
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return data;
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}
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fromJSON( json ) {
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super.fromJSON( json );
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this.degree = json.degree;
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this.knots = [ ...json.knots ];
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this.controlPoints = json.controlPoints.map( p => new Vector4( p[ 0 ], p[ 1 ], p[ 2 ], p[ 3 ] ) );
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this.startKnot = json.startKnot;
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this.endKnot = json.endKnot;
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return this;
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}
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}
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export { NURBSCurve };
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