Fixed normals/tangents generation in cylinder. Closes away3d#209

Now properly respects the slope of the lateral surface,
meaning that cones will now get slanting normals instead
of normals that are parallel with the base plane. Also
fixes issue when radius = 0, which it will always be for
one segment in cones. This previously resulted in zero
normals, which is no longer the case.

src/away3d/primitives/ConeGeometry.as

@@ -31,7 +31,7 @@ package away3d.primitives
 		 */
 		public function ConeGeometry(radius : Number = 50, height : Number = 100, segmentsW : uint = 16, segmentsH : uint = 1, closed:Boolean = true, yUp : Boolean = true)
 		{
-			super(0.00001, radius, height, segmentsW, segmentsH, false, closed, yUp);
+			super(0, radius, height, segmentsW, segmentsH, false, closed, yUp);
 		}
 	}
 }

src/away3d/primitives/CylinderGeometry.as

@@ -63,6 +63,7 @@ package away3d.primitives
 		{
 			var i:uint, j:uint;
 			var x:Number, y:Number, z:Number, radius:Number, revolutionAngle:Number;
+			var dr : Number, latNormElev : Number, latNormBase : Number;
 
 			// reset utility variables
 			_numVertices = 0;
@@ -104,7 +105,7 @@ package away3d.primitives
 			var revolutionAngleDelta:Number = 2 * Math.PI / _segmentsW;
 
 			// top
-			if (_topClosed) {
+			if (_topClosed && _topRadius > 0) {
 
 				z = -0.5 * _height;
 
@@ -132,7 +133,7 @@ package away3d.primitives
 			}
 
 			// bottom
-			if (_bottomClosed) {
+			if (_bottomClosed && _bottomRadius > 0) {
 
 				z = 0.5 * _height;
 
@@ -159,11 +160,21 @@ package away3d.primitives
 
 				_vertexIndexOffset = _nextVertexIndex;
 			}
+
+			// The normals on the lateral surface all have the same incline, i.e.
+			// the "elevation" component (Y or Z depending on yUp) is constant.
+			// Same principle goes for the "base" of these vectors, which will be
+			// calculated such that a vector [base,elev] will be a unit vector.
+			dr = (_bottomRadius - _topRadius);
+			latNormElev = dr / _height;
+			latNormBase = (latNormElev==0)? 1 : _height / dr;
+
 
 			// lateral surface
 			if(_surfaceClosed)
 			{
 				var a:uint, b:uint, c:uint, d:uint;
+				var na0 : Number, na1 : Number;
 
 				for(j = 0; j <= _segmentsH; ++j)
 				{
@@ -176,15 +187,17 @@ package away3d.primitives
 						revolutionAngle = i * revolutionAngleDelta;
 						x = radius * Math.cos(revolutionAngle);
 						y = radius * Math.sin(revolutionAngle);
-						var tanLen:Number = Math.sqrt(y * y + x * x);
+						na0 = latNormBase * Math.cos(revolutionAngle);
+						na1 = latNormBase * Math.sin(revolutionAngle);
+
 						if(_yUp)
 							addVertex(x, -z, y,
-									  x / tanLen, 0, y / tanLen,
-									  tanLen > .007 ? -y / tanLen : 1, 0, tanLen > .007 ? x / tanLen : 0);
+									  na0, latNormElev, na1,
+									  na1, 0, -na0);
 						else
 							addVertex(x, y, z,
-									  x / tanLen, y / tanLen, 0,
-									  tanLen > .007 ? -y / tanLen : 1, tanLen > .007 ? x / tanLen : 0, 0);
+									  na0, na1, latNormElev,
+									  na1, -na0, 0);
 
 						// close triangle
 						if(i > 0 && j > 0)