Fix T75936: Alembic, allow exporting of invisible objects

Add a new depsgraph builder class that includes invisible objects and
use that in the Alembic exporter.

Alembic supports three options for visibility, "visible", "inherited",
and "hidden". This means that parents can be hidden and still have
visible children (contrary to USD, where invisibility is used to prune
an entire scene graph subtree). Because of this, the visibility is
stored on the transform node, as that represents the Object in Blender
and thus keeps the Alembic file as close to Blender's own structure as
possible.

Reviewed By: Sergey

Differential Revision: https://developer.blender.org/D8595

source/blender/depsgraph/intern/builder/pipeline_all_objects.cc

@@ -0,0 +1,80 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+#include "pipeline_all_objects.h"
+
+#include "intern/builder/deg_builder_nodes.h"
+#include "intern/builder/deg_builder_relations.h"
+#include "intern/depsgraph.h"
+
+#include "DNA_layer_types.h"
+
+namespace blender {
+namespace deg {
+
+namespace {
+
+class AllObjectsNodeBuilder : public DepsgraphNodeBuilder {
+ public:
+  AllObjectsNodeBuilder(Main *bmain, Depsgraph *graph, DepsgraphBuilderCache *cache)
+      : DepsgraphNodeBuilder(bmain, graph, cache)
+  {
+  }
+
+  virtual bool need_pull_base_into_graph(Base * /*base*/) override
+  {
+    return true;
+  }
+};
+
+class AllObjectsRelationBuilder : public DepsgraphRelationBuilder {
+ public:
+  AllObjectsRelationBuilder(Main *bmain, Depsgraph *graph, DepsgraphBuilderCache *cache)
+      : DepsgraphRelationBuilder(bmain, graph, cache)
+  {
+  }
+
+  virtual bool need_pull_base_into_graph(Base * /*base*/) override
+  {
+    return true;
+  }
+};
+
+}  // namespace
+
+AllObjectsBuilderPipeline::AllObjectsBuilderPipeline(::Depsgraph *graph,
+                                                     Main *bmain,
+                                                     Scene *scene,
+                                                     ViewLayer *view_layer)
+    : ViewLayerBuilderPipeline(graph, bmain, scene, view_layer)
+{
+}
+
+unique_ptr<DepsgraphNodeBuilder> AllObjectsBuilderPipeline::construct_node_builder()
+{
+  return std::make_unique<AllObjectsNodeBuilder>(bmain_, deg_graph_, &builder_cache_);
+}
+
+unique_ptr<DepsgraphRelationBuilder> AllObjectsBuilderPipeline::construct_relation_builder()
+{
+  return std::make_unique<AllObjectsRelationBuilder>(bmain_, deg_graph_, &builder_cache_);
+}
+
+}  // namespace deg
+}  // namespace blender