Improve appleseed-max object plugins support

src/appleseed-max-common/iappleseedgeometricobject.h

@@ -58,6 +58,17 @@ class IAppleseedGeometricObject
     // BaseInterface methods.
     Interface_ID GetID() override;
 
+    enum Flags
+    {
+        // When the IgnoreTransform flag is set, the object will always be exported with an identity transform.
+        // This is useful for "linked objects", i.e. objects that define themselves in relation to an instance
+        // of another object, in which case they naturally inherit the transform of that other object instance.
+        IgnoreTransform = 1UL << 0
+    };
+
+    // Retrieve the flags of this object.
+    virtual int get_flags() const = 0;
+
     // Create an appleseed geometric object.
     virtual foundation::auto_release_ptr<renderer::Object> create_object(
         renderer::Project&  project,

src/appleseed-max-impl/appleseedrenderer/projectbuilder.cpp

@@ -162,6 +162,27 @@ namespace
         return name;
     }
 
+    // Return the IAppleseedGeometricObject interface of an object, even if this object has modifiers applied to it.
+    static IAppleseedGeometricObject* get_appleseed_geometric_object(Object* object)
+    {
+        IAppleseedGeometricObject* result = nullptr;
+
+        while (object != nullptr)
+        {
+            result = static_cast<IAppleseedGeometricObject*>(object->GetInterface(IAppleseedGeometricObject::interface_id()));
+
+            if (result != nullptr)
+                break;
+
+            if (object->SuperClassID() != GEN_DERIVOB_CLASS_ID)
+                break;
+
+            object = static_cast<IDerivedObject*>(object)->GetObjRef();
+        }
+
+        return result;
+    }
+
     class NullView
       : public View
     {
@@ -418,12 +439,14 @@ namespace
         Object* object = object_node->GetObjectRef();
 
         // Check if this object is defined by an appleseed-max plugin.
-        auto appleseed_geo_object =
-            static_cast<IAppleseedGeometricObject*>(object->GetInterface(IAppleseedGeometricObject::interface_id()));
+        IAppleseedGeometricObject* appleseed_geo_object = get_appleseed_geometric_object(object);
 
-        if (appleseed_geo_object)
+        if (appleseed_geo_object != nullptr)
         {
+            // This object is an appleseed-max object plugin: create the appleseed object and insert it into the assembly.
+
             ObjectInfo object_info;
+            object_info.m_appleseed_geo_object = appleseed_geo_object;
             object_info.m_name = wide_to_utf8(object_node->GetName());
             object_info.m_name = make_unique_name(assembly.objects(), object_info.m_name);
 
@@ -443,6 +466,7 @@ namespace
         }
         else
         {
+            // This object is not an appleseed-max object plugin: export the object as one or multiple mesh objects.
             return create_mesh_objects(assembly, object_node, time);
         }
     }
@@ -813,15 +837,23 @@ namespace
         if (type == RenderType::MaterialPreview)
             params.insert_path("visibility.shadow", false);
 
+        // Instance of helper objects always have an identity transform.
+        const asf::Transformd effective_transform =
+            object_info.m_appleseed_geo_object != nullptr &&
+            (object_info.m_appleseed_geo_object->get_flags() & IAppleseedGeometricObject::IgnoreTransform)
+                ? asf::Transformd::identity()
+                : transform;
+
         // Create the instance and insert it into the assembly.
-        const size_t instance_index = assembly.object_instances().insert(
-            asr::ObjectInstanceFactory::create(
-                instance_name.c_str(),
-                params,
-                object_info.m_name.c_str(),
-                transform,
-                front_material_mappings,
-                back_material_mappings));
+        const size_t instance_index =
+            assembly.object_instances().insert(
+                asr::ObjectInstanceFactory::create(
+                    instance_name.c_str(),
+                    params,
+                    object_info.m_name.c_str(),
+                    effective_transform,
+                    front_material_mappings,
+                    back_material_mappings));
 
         obj_instance_map[wide_to_utf8(instance_node->GetName())] = assembly.object_instances().get_by_index(instance_index);
     }

src/appleseed-max-impl/appleseedrenderer/projectbuilder.h

@@ -49,15 +49,14 @@
 
 // Forward declarations.
 namespace renderer { class Assembly; }
+namespace renderer { class AssemblyInstance; }
 namespace renderer { class Camera; }
-namespace renderer { class Entity; }
 namespace renderer { class ObjectInstance; }
-namespace renderer { class AssemblyInstance; }
-namespace renderer { class ParamArray; }
 namespace renderer { class Project; }
 class Bitmap;
-class IAppleseedMtl;
 class FrameRendParams;
+class IAppleseedGeometricObject;
+class IAppleseedMtl;
 class MaxSceneEntities;
 class RendParams;
 class ViewParams;
@@ -70,9 +69,10 @@ enum class RenderType
 
 struct ObjectInfo
 {
-    std::string                                 m_name;                 // name of the appleseed object
-    std::map<MtlID, std::string>                m_mtlid_to_slot_name;   // map a Max's material ID to appleseed's material slot name
-    std::map<MtlID, std::uint32_t>              m_mtlid_to_slot_index;  // map a Max's material ID to appleseed's material slot index
+    IAppleseedGeometricObject*          m_appleseed_geo_object = {};    // appleseed-max geometric object interface implemented by the 3ds Max object
+    std::string                         m_name;                         // name of the appleseed object
+    std::map<MtlID, std::string>        m_mtlid_to_slot_name;           // map a Max's material ID to an appleseed's material slot name
+    std::map<MtlID, std::uint32_t>      m_mtlid_to_slot_index;          // map a Max's material ID to an appleseed's material slot index
 };
 
 typedef std::map<Object*, std::vector<ObjectInfo>> ObjectMap;