Merge remote-tracking branch 'origin/master' into blender2.8

source/blender/modifiers/intern/MOD_meshsequencecache.c

@@ -65,6 +65,7 @@ static void copyData(ModifierData *md, ModifierData *target)
 
 	if (tmcmd->cache_file) {
 		id_us_plus(&tmcmd->cache_file->id);
+		tmcmd->reader = NULL;
 	}
 }
 
@@ -75,6 +76,12 @@ static void freeData(ModifierData *md)
 	if (mcmd->cache_file) {
 		id_us_min(&mcmd->cache_file->id);
 	}
+
+	if (mcmd->reader) {
+#ifdef WITH_ALEMBIC
+		CacheReader_free(mcmd->reader);
+#endif
+	}
 }
 
 static bool isDisabled(ModifierData *md, int UNUSED(useRenderParams))
@@ -102,10 +109,16 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 
 	BKE_cachefile_ensure_handle(G.main, cache_file);
 
-	DerivedMesh *result = ABC_read_mesh(cache_file->handle,
+	if (!mcmd->reader) {
+		mcmd->reader = CacheReader_open_alembic_object(cache_file->handle,
+		                                               mcmd->reader,
+		                                               ob,
+		                                               mcmd->object_path);
+	}
+
+	DerivedMesh *result = ABC_read_mesh(mcmd->reader,
 	                                    ob,
 	                                    dm,
-	                                    mcmd->object_path,
 	                                    time,
 	                                    &err_str,
 	                                    mcmd->read_flag);