add multimaterial per mesh support

Author: vkovec

Assets/FbxExporters/Editor/FbxExporter.cs

@@ -264,14 +264,13 @@ public FbxDouble3 GetMaterialColor (Material unityMaterial, string unityPropName
             /// <summary>
             /// Export (and map) a Unity PBS material to FBX classic material
             /// </summary>
-            public FbxSurfaceMaterial ExportMaterial (Material unityMaterial, FbxScene fbxScene, FbxMesh fbxMesh)
+            public FbxSurfaceMaterial ExportMaterial (Material unityMaterial, FbxScene fbxScene)
             {
                 if (Verbose)
                     Debug.Log (string.Format ("exporting material {0}", unityMaterial.name));
 
                 var materialName = unityMaterial ? unityMaterial.name : "DefaultMaterial";
                 if (MaterialMap.ContainsKey (materialName)) {
-                    AssignLayerElementMaterial (fbxMesh);
                     return MaterialMap [materialName];
                 }
 
@@ -303,13 +302,11 @@ public FbxSurfaceMaterial ExportMaterial (Material unityMaterial, FbxScene fbxSc
                     ExportTexture (unityMaterial, "_SpecGlosMap", fbxMaterial, FbxSurfaceMaterial.sSpecular);
                 }
 
-                AssignLayerElementMaterial (fbxMesh);
-
                 MaterialMap.Add (materialName, fbxMaterial);
                 return fbxMaterial;
             }
 
-            private void AssignLayerElementMaterial(FbxMesh fbxMesh)
+            private void AssignLayerElementMaterial(FbxMesh fbxMesh, Mesh mesh, Material[] materials)
             {
                 // Add FbxLayerElementMaterial to layer 0 of the node
                 FbxLayer fbxLayer = fbxMesh.GetLayer (0 /* default layer */);
@@ -320,13 +317,20 @@ private void AssignLayerElementMaterial(FbxMesh fbxMesh)
 
                 using (var fbxLayerElement = FbxLayerElementMaterial.Create (fbxMesh, "Material")) {
                     // Using all same means that the entire mesh uses the same material
-                    fbxLayerElement.SetMappingMode (FbxLayerElement.EMappingMode.eAllSame);
+                    fbxLayerElement.SetMappingMode (FbxLayerElement.EMappingMode.eByPolygon);
                     fbxLayerElement.SetReferenceMode (FbxLayerElement.EReferenceMode.eIndexToDirect);
 
                     FbxLayerElementArray fbxElementArray = fbxLayerElement.GetIndexArray ();
+                    fbxElementArray.SetCount (mesh.triangles.Length / 3);
 
                     // Map the entire geometry to the FbxNode material at index 0
-                    fbxElementArray.Add (0);
+                    for (int i = 0; i < mesh.subMeshCount; i++) {
+                        int start = ((int)mesh.GetIndexStart (i))/3;
+                        int count = ((int)mesh.GetIndexCount (i))/3;
+                        for (int j = start; j < start + count; j++) {
+                            fbxElementArray.SetAt (j, i);
+                        }
+                    }
                     fbxLayer.SetMaterials (fbxLayerElement);
                 }
             }
@@ -387,8 +391,10 @@ meshInfo.Vertices [v].z*UnitScaleFactor
                     }
                 }
 
-                var fbxMaterial = ExportMaterial (meshInfo.Material, fbxScene, fbxMesh);
-                fbxNode.AddMaterial (fbxMaterial);
+                foreach (var mat in meshInfo.Materials) {
+                    var fbxMaterial = ExportMaterial (mat, fbxScene);
+                    fbxNode.AddMaterial (fbxMaterial);
+                }
 
                 /*
                  * Triangles have to be added in reverse order, 
@@ -419,6 +425,8 @@ meshInfo.Vertices [v].z*UnitScaleFactor
                     fbxMesh.EndPolygon ();
                 }
 
+                AssignLayerElementMaterial (fbxMesh, meshInfo.mesh, meshInfo.Materials);
+
                 ExportComponentAttributes (meshInfo, fbxMesh, unmergedTriangles);
 
                 // set the fbxNode containing the mesh
@@ -855,7 +863,7 @@ public Vector3 [] Binormals {
                 /// The material used, if any; otherwise null.
                 /// We don't support multiple materials on one gameobject.
                 /// </summary>
-                public Material Material {
+                public Material[] Materials {
                     get {
                         if (!unityObject) {
                             return null;
@@ -866,12 +874,14 @@ public Material Material {
                         }
 
                         if (FbxExporters.EditorTools.ExportSettings.instance.mayaCompatibleNames) {
-                            renderer.sharedMaterial.name = ConvertToMayaCompatibleName (renderer.sharedMaterial.name);
+                            foreach (var mat in renderer.sharedMaterials) {
+                                mat.name = ConvertToMayaCompatibleName (mat.name);
+                            }
                         }
 
                         // .material instantiates a new material, which is bad
                         // most of the time.
-                        return renderer.sharedMaterial;
+                        return renderer.sharedMaterials;
                     }
                 }