Accueil / npm / three@0.186.1 / examples / jsm / curves / NURBSCurve.js
NURBSCurve.js
import {
Curve,
Vector3,
Vector4
} from 'three';
import * as NURBSUtils from '../curves/NURBSUtils.js';
/**
* This class represents a NURBS curve.
*
* Implementation is based on `(x, y [, z=0 [, w=1]])` control points with `w=weight`.
*
* @augments Curve
* @three_import import { NURBSCurve } from 'three/addons/curves/NURBSCurve.js';
*/
class NURBSCurve extends Curve {
/**
* Constructs a new NURBS curve.
*
* @param {number} degree - The NURBS degree.
* @param {Array<number>} knots - The knots as a flat array of numbers.
* @param {Array<Vector2|Vector3|Vector4>} controlPoints - An array holding control points.
* @param {number} [startKnot] - Index of the start knot into the `knots` array.
* @param {number} [endKnot] - Index of the end knot into the `knots` array.
*/
constructor( degree, knots, controlPoints, startKnot, endKnot ) {
super();
const knotsLength = knots ? knots.length - 1 : 0;
const pointsLength = controlPoints ? controlPoints.length : 0;
/**
* The NURBS degree.
*
* @type {number}
*/
this.degree = degree;
/**
* The knots as a flat array of numbers.
*
* @type {Array<number>}
*/
this.knots = knots;
/**
* An array of control points.
*
* @type {Array<Vector4>}
*/
this.controlPoints = [];
/**
* Index of the start knot into the `knots` array.
*
* @type {number}
*/
this.startKnot = startKnot || 0;
/**
* Index of the end knot into the `knots` array.
*
* @type {number}
*/
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 );
}
}
/**
* This method returns a vector in 3D space for the given interpolation factor.
*
* @param {number} t - A interpolation factor representing a position on the curve. Must be in the range `[0,1]`.
* @param {Vector3} [optionalTarget] - The optional target vector the result is written to.
* @return {Vector3} The position on the curve.
*/
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 );
}
/**
* Returns a unit vector tangent for the given interpolation factor.
*
* @param {number} t - The interpolation factor.
* @param {Vector3} [optionalTarget] - The optional target vector the result is written to.
* @return {Vector3} The tangent vector.
*/
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 };