Merge pull request #2 from Unity-Technologies/UNI-20449-fix-inverted-triangles

UNI-20449 fix so triangles are not inverted when exported

Author: inwoods

Assets/Editor/FbxExporter.cs

@@ -204,20 +204,26 @@ public void ExportMesh (MeshInfo meshInfo, FbxNode fbxNode, FbxScene fbxScene)
                 // copy control point data from Unity to FBX
                 for (int v = 0; v < NumControlPoints; v++)
                 {
-                    fbxMesh.SetControlPointAt(new FbxVector4 (meshInfo.Vertices [v].x, meshInfo.Vertices [v].y, meshInfo.Vertices [v].z), v);
+                    // convert from left to right-handed by negating x (Unity negates x again on import)
+                    fbxMesh.SetControlPointAt(new FbxVector4 (-meshInfo.Vertices [v].x, meshInfo.Vertices [v].y, meshInfo.Vertices [v].z), v);
                 }
 
                 ExportUVs (meshInfo, fbxMesh);
 
                 var fbxMaterial = ExportMaterial (meshInfo.Material, fbxScene);
                 fbxNode.AddMaterial (fbxMaterial);
 
+                /*
+                 * Triangles have to be added in reverse order, 
+                 * or else they will be inverted on import 
+                 * (due to the conversion from left to right handed coords)
+                 */
                 for (int f = 0; f < meshInfo.Triangles.Length / 3; f++)
                 {
                     fbxMesh.BeginPolygon ();
-                    fbxMesh.AddPolygon (meshInfo.Triangles [3 * f]);
-                    fbxMesh.AddPolygon (meshInfo.Triangles [3 * f + 1]);
                     fbxMesh.AddPolygon (meshInfo.Triangles [3 * f + 2]);
+                    fbxMesh.AddPolygon (meshInfo.Triangles [3 * f + 1]);
+                    fbxMesh.AddPolygon (meshInfo.Triangles [3 * f]);
                     fbxMesh.EndPolygon ();
                 }
 
@@ -235,8 +241,10 @@ protected void ExportTransform (UnityEngine.Transform unityTransform, FbxNode fb
                 UnityEngine.Vector3 unityScale = unityTransform.localScale;
 
                 // transfer transform data from Unity to Fbx
-                var fbxTranslate = new FbxDouble3 (unityTranslate.x, unityTranslate.y, unityTranslate.z);
-                var fbxRotate = new FbxDouble3 (unityRotate.x, unityRotate.y, unityRotate.z);
+                // Negating the x value of the translation, and the y and z values of the rotation
+                // to convert from Unity to Maya coordinates (left to righthanded)
+                var fbxTranslate = new FbxDouble3 (-unityTranslate.x, unityTranslate.y, unityTranslate.z);
+                var fbxRotate = new FbxDouble3 (unityRotate.x, -unityRotate.y, -unityRotate.z);
                 var fbxScale = new FbxDouble3 (unityScale.x, unityScale.y, unityScale.z);
 
                 // set the local position of fbxNode