three-stdlib/curves/NURBSCurve.js

stand-alone library of threejs examples

import { Curve, Vector4, Vector3 } from "three";
import { calcBSplinePoint, calcNURBSDerivatives } from "./NURBSUtils.js";
class NURBSCurve extends Curve {
  constructor(degree, knots, controlPoints, startKnot, endKnot) {
    super();
    this.degree = degree;
    this.knots = knots;
    this.controlPoints = [];
    this.startKnot = startKnot || 0;
    this.endKnot = endKnot || this.knots.length - 1;
    for (let i = 0; i < controlPoints.length; ++i) {
      const point = controlPoints[i];
      this.controlPoints[i] = new Vector4(point.x, point.y, point.z, point.w);
    }
  }
  getPoint(t, optionalTarget) {
    const point = optionalTarget || new Vector3();
    const u = this.knots[this.startKnot] + t * (this.knots[this.endKnot] - this.knots[this.startKnot]);
    const hpoint = calcBSplinePoint(this.degree, this.knots, this.controlPoints, u);
    if (hpoint.w != 1) {
      hpoint.divideScalar(hpoint.w);
    }
    return point.set(hpoint.x, hpoint.y, hpoint.z);
  }
  getTangent(t, optionalTarget) {
    const tangent = optionalTarget || new Vector3();
    const u = this.knots[0] + t * (this.knots[this.knots.length - 1] - this.knots[0]);
    const ders = calcNURBSDerivatives(this.degree, this.knots, this.controlPoints, u, 1);
    tangent.copy(ders[1]).normalize();
    return tangent;
  }
}
export {
  NURBSCurve
};
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