Geometry.toJSON(): Added materialIndex support. See #7415.

src/core/Geometry.js

@@ -960,7 +960,7 @@ THREE.Geometry.prototype = {
 
 			var face = this.faces[ i ];
 
-			var hasMaterial = false; // face.materialIndex !== undefined;
+			var hasMaterial = true;
 			var hasFaceUv = false; // deprecated
 			var hasFaceVertexUv = this.faceVertexUvs[ 0 ][ i ] !== undefined;
 			var hasFaceNormal = face.normal.length() > 0;
@@ -970,7 +970,7 @@ THREE.Geometry.prototype = {
 
 			var faceType = 0;
 
-			faceType = setBit( faceType, 0, 0 );
+			faceType = setBit( faceType, 0, 0 ); // isQuad
 			faceType = setBit( faceType, 1, hasMaterial );
 			faceType = setBit( faceType, 2, hasFaceUv );
 			faceType = setBit( faceType, 3, hasFaceVertexUv );
@@ -981,6 +981,7 @@ THREE.Geometry.prototype = {
 
 			faces.push( faceType );
 			faces.push( face.a, face.b, face.c );
+			faces.push( face.materialIndex );
 
 			if ( hasFaceVertexUv ) {