Update stlSerializer.ts

Last minute changes..
Removed n vector3 negating & switched the input values as suggested.
Updated default fileName to match binary mesh name (which is always 'stlmesh')
Updated ASCII mesh name to match binary mesh name for consistency
And removed fileName check in download code as it is defaulted at beginning.

serializers/src/stl/stlSerializer.ts

@@ -15,7 +15,7 @@ export class STLExport {
     * @param isLittleEndian toggle for binary type exporter.
     * @returns the STL as UTF8 string
     */
-    public static CreateSTL(meshes: Mesh[], download: boolean = true, fileName: string = 'STL_Mesh', binary: boolean = false, isLittleEndian: boolean = true): any {
+    public static CreateSTL(meshes: Mesh[], download: boolean = true, fileName: string = 'stlmesh', binary: boolean = false, isLittleEndian: boolean = true): any {
 
         //Binary support adapted from https://gist.github.com/paulkaplan/6d5f0ab2c7e8fdc68a61
 
@@ -28,7 +28,7 @@ export class STLExport {
             ];
             let p1p2 = v[0].subtract(v[1]);
             let p3p2 = v[2].subtract(v[1]);
-            let n = (Vector3.Cross(p1p2, p3p2)).normalize().negateInPlace();
+            let n = (Vector3.Cross(p3p2, p1p2)).normalize();
 
             return {v, n};
         };
@@ -65,7 +65,7 @@ export class STLExport {
             offset += 4;
 
         } else {
-            data = 'solid exportedMesh\r\n';
+            data = 'solid stlmesh\r\n';
         }
 
         for (let i = 0; i < meshes.length; i++) {
@@ -97,17 +97,13 @@ export class STLExport {
         }
 
         if (!binary) {
-            data += 'endsolid exportedMesh';
+            data += 'endsolid stlmesh';
         }
 
         if (download) {
             let a = document.createElement('a');
             let blob = new Blob([data], {'type': 'application/octet-stream'});
             a.href = window.URL.createObjectURL(blob);
-
-            if (!fileName) {
-                fileName = "STL_Mesh";
-            }
             a.download = fileName + ".stl";
             a.click();
         }