Doodle3D-Slicer/three.js-master/examples/js/curves/NURBSCurve.js

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2015-06-12 15:58:26 +02:00
/**
* @author renej
* 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.
*
**/
/**************************************************************
* NURBS curve
**************************************************************/
THREE.NURBSCurve = function ( degree, knots /* array of reals */, controlPoints /* array of Vector(2|3|4) */) {
this.degree = degree;
this.knots = knots;
this.controlPoints = [];
for (var i = 0; i < controlPoints.length; ++ i) { // ensure Vector4 for control points
var point = controlPoints[i];
this.controlPoints[i] = new THREE.Vector4(point.x, point.y, point.z, point.w);
}
};
THREE.NURBSCurve.prototype = Object.create( THREE.Curve.prototype );
THREE.NURBSCurve.prototype.constructor = THREE.NURBSCurve;
THREE.NURBSCurve.prototype.getPoint = function ( t ) {
var u = this.knots[0] + t * (this.knots[this.knots.length - 1] - this.knots[0]); // linear mapping t->u
// following results in (wx, wy, wz, w) homogeneous point
var hpoint = THREE.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 new THREE.Vector3(hpoint.x, hpoint.y, hpoint.z);
};
THREE.NURBSCurve.prototype.getTangent = function ( t ) {
var u = this.knots[0] + t * (this.knots[this.knots.length - 1] - this.knots[0]);
var ders = THREE.NURBSUtils.calcNURBSDerivatives(this.degree, this.knots, this.controlPoints, u, 1);
var tangent = ders[1].clone();
tangent.normalize();
return tangent;
};