Fix FBX shape naming for blendshapes

If the name of a FbxShape backing a blendshape channel is left as an empty string, multiple blend shapes on the same object fail to export properly. Only the last blendshape modifier is used, regardless of which is enabled. This fixes it.

Author: lazlo-bonin

com.unity.formats.fbx/Editor/FbxExporter.cs

@@ -498,7 +498,14 @@ private bool ExportBlendShapes(MeshInfo mesh, FbxMesh fbxMesh, FbxScene fbxScene
                     var weight = umesh.GetBlendShapeFrameWeight(bi, fi);
                     umesh.GetBlendShapeFrameVertices(bi, fi, deltaPoints, deltaNormals, deltaTangents);
 
-                    var fbxShape = FbxShape.Create(fbxScene, "");
+                    var fbxShapeName = bsName;
+
+                    if (numFrames > 1)
+                    {
+                        fbxShapeName += "_" + fi;
+                    }
+
+                    var fbxShape = FbxShape.Create(fbxScene, fbxShapeName);
                     fbxChannel.AddTargetShape(fbxShape, weight);
 
                     // control points