added an optional function taper to THREE.TubeGeometry to customize v…

…ertex projections

src/extras/geometries/TubeGeometry.js

@@ -2,6 +2,7 @@
  * @author WestLangley / https://github.com/WestLangley
  * @author zz85 / https://github.com/zz85
  * @author miningold / https://github.com/miningold
+ * @author jonobr1 / https://github.com/jonobr1
  *
  * Modified from the TorusKnotGeometry by @oosmoxiecode
  *
@@ -11,7 +12,7 @@
  * http://www.cs.indiana.edu/pub/techreports/TR425.pdf
  */
 
-THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed ) {
+THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed, taper ) {
 
 	THREE.Geometry.call( this );
 
@@ -29,6 +30,7 @@ THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed )
 	radius = radius || 1;
 	radialSegments = radialSegments || 8;
 	closed = closed || false;
+	taper = taper || THREE.TubeGeometry.NoTaper;
 
 	var grid = [];
 
@@ -42,7 +44,7 @@ THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed )
 
 		x, y, z,
 		tx, ty, tz,
-		u, v,
+		u, v, r,
 
 		cx, cy,
 		pos, pos2 = new THREE.Vector3(),
@@ -81,12 +83,14 @@ THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed )
 		normal = normals[ i ];
 		binormal = binormals[ i ];
 
+		r = radius * taper(u);
+
 		for ( j = 0; j < radialSegments; j ++ ) {
 
 			v = j / radialSegments * 2 * Math.PI;
 
-			cx = - radius * Math.cos( v ); // TODO: Hack: Negating it so it faces outside.
-			cy = radius * Math.sin( v );
+			cx = - r * Math.cos( v ); // TODO: Hack: Negating it so it faces outside.
+			cy = r * Math.sin( v );
 
 			pos2.copy( pos );
 			pos2.x += cx * normal.x + cy * binormal.x;
@@ -135,6 +139,13 @@ THREE.TubeGeometry = function ( path, segments, radius, radialSegments, closed )
 THREE.TubeGeometry.prototype = Object.create( THREE.Geometry.prototype );
 THREE.TubeGeometry.prototype.constructor = THREE.TubeGeometry;
 
+THREE.TubeGeometry.NoTaper = function(u) {
+	return u;
+};
+
+THREE.TubeGeometry.SinusoidalTaper = function(u) {
+	return Math.sin(Math.PI * u);
+};
 
 // For computing of Frenet frames, exposing the tangents, normals and binormals the spline
 THREE.TubeGeometry.FrenetFrames = function ( path, segments, closed ) {