three
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JavaScript 3D library
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JavaScript
console.warn( "THREE.NURBSCurve: As part of the transition to ES6 Modules, the files in 'examples/js' were deprecated in May 2020 (r117) and will be deleted in December 2020 (r124). You can find more information about developing using ES6 Modules in https://threejs.org/docs/#manual/en/introduction/Installation." );
/**
* 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.
*
**/
THREE.NURBSCurve = function ( degree, knots /* array of reals */, controlPoints /* array of Vector(2|3|4) */, startKnot /* index in knots */, endKnot /* index in knots */ ) {
THREE.Curve.call( this );
this.degree = degree;
this.knots = knots;
this.controlPoints = [];
// Used by periodic NURBS to remove hidden spans
this.startKnot = startKnot || 0;
this.endKnot = endKnot || ( this.knots.length - 1 );
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, optionalTarget ) {
var point = optionalTarget || new THREE.Vector3();
var 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
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 point.set( hpoint.x, hpoint.y, hpoint.z );
};
THREE.NURBSCurve.prototype.getTangent = function ( t, optionalTarget ) {
var tangent = optionalTarget || new THREE.Vector3();
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 );
tangent.copy( ders[ 1 ] ).normalize();
return tangent;
};