Merge pull request #6302 from pavelvasev/dev

BufferGeometry: return the number of hit triangle in raycast

src/objects/Mesh.js

@@ -159,9 +159,9 @@ THREE.Mesh.prototype.raycast = ( function () {
 							distance: distance,
 							point: intersectionPoint,
 							face: new THREE.Face3( a, b, c, THREE.Triangle.normal( vA, vB, vC ) ),
-							faceIndex: null,
+							faceIndex: Math.floor(i/3), // triangle number in indices buffer semantics
 							object: this
-
+							
 						} );
 
 					}
@@ -205,7 +205,7 @@ THREE.Mesh.prototype.raycast = ( function () {
 						distance: distance,
 						point: intersectionPoint,
 						face: new THREE.Face3( a, b, c, THREE.Triangle.normal( vA, vB, vC ) ),
-						faceIndex: null,
+						index: Math.floor(i/3), // triangle number in positions buffer semantics
 						object: this
 
 					} );