Refactored Mesh.CreateCylinder

Now this method uses the CreateTube method with simplified parameters, and a specific way of adding caps.
Fixes the normal discontinuity on existing cylinders.

Example here: http://www.babylonjs-playground.com/#1S6POH#1
Left cylinders are created using the old method, and right cylinders using the new one.

Please note:
- the UV mapping is shifted by PI/2 on the cylinder side (probably fixable for backwards compatiblity purposes)
- this renders the VertexData.CreateCylinder method useless.

src/Mesh/babylon.mesh.ts

@@ -1354,11 +1354,61 @@
                 subdivisions = 1;
             }
 
-            var cylinder = new Mesh(name, scene);
-            var vertexData = VertexData.CreateCylinder(height, diameterTop, diameterBottom, tessellation, subdivisions);
-
-            vertexData.applyToMesh(cylinder, updatable);
-
+            // setup tube creation parameters
+        	var path = [
+        		new Vector3(0, -height/2, 0), 
+        		new Vector3(0, height/2, 0), 
+        	];
+        	
+        	var radiusFunction = function (i, distance) {
+        		return (diameterBottom + (diameterTop - diameterBottom) * distance / height)/2;
+        	};
+        	
+        	// create tube without caps
+        	var cylinder = Mesh.CreateTube(name, path, 1.0, tessellation, radiusFunction, Mesh.NO_CAP, scene, updatable, sideOrientation);
+        	
+        	// extract geometry data to add caps
+        	var geometry_data = VertexData.ExtractFromMesh(cylinder);
+        	
+        	var createCylinderCap = function (isTop) {
+        	    var radius = isTop ? diameterTop/2 : diameterBottom/2;
+        	    if (radius === 0) {
+        	        return;
+        		}
+        	    var vbase = geometry_data.positions.length / 3;
+        		var offset = new Vector3(0, isTop ? height / 2 : -height / 2, 0);
+        	    var textureScale = new Vector2(0.5, 0.5);
+        	    // Positions, normals & uvs
+        		var angle;
+        		for (var i = 0; i < tessellation; i++) {
+        			angle = Math.PI * 2 * i / tessellation;
+        	        var circleVector = new Vector3(Math.cos(angle), 0, Math.sin(angle));
+        	        var position = circleVector.scale(radius).add(offset);
+        	        var textureCoordinate = new Vector2(circleVector.x * textureScale.x + 0.5, circleVector.z * textureScale.y + 0.5);
+        			geometry_data.positions.push(position.x, position.y, position.z);
+        			geometry_data.normals.push(0, 1, 0);
+        	        geometry_data.uvs.push(textureCoordinate.x, textureCoordinate.y);
+        	    }
+        	    // Indices
+        	    for (i = 0; i < tessellation - 2; i++) {
+        	        if (!isTop) {
+        	            geometry_data.indices.push(vbase);
+        	            geometry_data.indices.push(vbase + (i + 2) % tessellation);
+        	            geometry_data.indices.push(vbase + (i + 1) % tessellation);
+        	        }
+        	        else {
+        	            geometry_data.indices.push(vbase);
+        	            geometry_data.indices.push(vbase + (i + 1) % tessellation);
+        	            geometry_data.indices.push(vbase + (i + 2) % tessellation);
+        	        }
+        	    }
+        	};
+        	
+        	// add caps to geometry and apply to mesh
+        	createCylinderCap(true);
+        	createCylinderCap(false);
+        	geometry_data.applyToMesh(cylinder);
+        
             return cylinder;
         }