Alembic: store a pointer to the object reader in the cache modifiers and

constraints.

This avoids traversing the archive everytime object data is needed and
gives an overall consistent ~2x speedup here with files containing
between 136 and 500 Alembic objects. Also this somewhat nicely de-
duplicates code between data creation (upon import) and data streaming
(modifiers and constraints).

The only worying part is what happens when a CacheFile is deleted and/or
has its path changed. For now, we traverse the whole scene and for each
object using the CacheFile we free the pointer and NULL-ify it (see
BKE_cachefile_clean), but at some point this should be re-considered and
make use of the dependency graph.

3 files changed, 51 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_cachefile.h b/source/blender/blenkernel/BKE_cachefile.h
index a55cb51766c..7e1c069df9a 100644
--- a/source/blender/blenkernel/BKE_cachefile.h
+++ b/source/blender/blenkernel/BKE_cachefile.h
@@ -63,6 +63,8 @@ bool BKE_cachefile_filepath_get(
 
 float BKE_cachefile_time_offset(struct CacheFile *cache_file, const float time, const float fps);
 
+void BKE_cachefile_clean(struct Scene *scene, struct CacheFile *cache_file);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/blender/blenkernel/intern/cachefile.c b/source/blender/blenkernel/intern/cachefile.c
index e62e652b4a6..2a2699f3a14 100644
--- a/source/blender/blenkernel/intern/cachefile.c
+++ b/source/blender/blenkernel/intern/cachefile.c
@@ -29,6 +29,8 @@
 
 #include "DNA_anim_types.h"
 #include "DNA_cachefile_types.h"
+#include "DNA_constraint_types.h"
+#include "DNA_object_types.h"
 #include "DNA_scene_types.h"
 
 #include "BLI_fileops.h"
@@ -43,6 +45,7 @@
 #include "BKE_global.h"
 #include "BKE_library.h"
 #include "BKE_main.h"
+#include "BKE_modifier.h"
 #include "BKE_scene.h"
 
 #ifdef WITH_ALEMBIC
@@ -196,3 +199,37 @@ float BKE_cachefile_time_offset(CacheFile *cache_file, const float time, const f
 	const float frame = (cache_file->override_frame ? cache_file->frame : time);
 	return cache_file->is_sequence ? frame : frame / fps;
 }
+
+/* TODO(kevin): replace this with some depsgraph mechanism, or something similar. */
+void BKE_cachefile_clean(Scene *scene, CacheFile *cache_file)
+{
+	for (Base *base = scene->base.first; base; base = base->next) {
+		Object *ob = base->object;
+
+		ModifierData *md = modifiers_findByType(ob, eModifierType_MeshSequenceCache);
+
+		if (md) {
+			MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)md;
+
+			if (cache_file == mcmd->cache_file) {
+				CacheReader_free(mcmd->reader);
+				mcmd->reader = NULL;
+				mcmd->object_path[0] = '\0';
+			}
+		}
+
+		for (bConstraint *con = ob->constraints.first; con; con = con->next) {
+			if (con->type != CONSTRAINT_TYPE_TRANSFORM_CACHE) {
+				continue;
+			}
+
+			bTransformCacheConstraint *data = con->data;
+
+			if (cache_file == data->cache_file) {
+				CacheReader_free(data->reader);
+				data->reader = NULL;
+				data->object_path[0] = '\0';
+			}
+		}
+	}
+}
diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index c4afa58b7d3..c7750707cc4 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -4364,8 +4364,14 @@ static void transformcache_evaluate(bConstraint *con, bConstraintOb *cob, ListBa
 
 	BKE_cachefile_ensure_handle(G.main, cache_file);
 
-	ABC_get_transform(cache_file->handle, cob->ob, data->object_path,
-	                  cob->matrix, time, cache_file->scale);
+	if (!data->reader) {
+		data->reader = CacheReader_open_alembic_object(cache_file->handle,
+		                                               data->reader,
+		                                               cob->ob,
+		                                               data->object_path);
+	}
+
+	ABC_get_transform(data->reader, cob->matrix, time, cache_file->scale);
 #else
 	UNUSED_VARS(con, cob);
 #endif
@@ -4393,6 +4399,10 @@ static void transformcache_free(bConstraint *con)
 	if (data->cache_file) {
 		id_us_min(&data->cache_file->id);
 	}
+
+	if (data->reader) {
+		CacheReader_free(data->reader);
+	}
 }
 
 static void transformcache_new_data(void *cdata)