Geometry Nodes: move geometry set instance handling to separate file

In an upcoming commit I'll also move the make-instances-real functionality
to this file. This code is not essential to working with geometry sets in general,
so it makes sense to move it to a separate header.

1 files changed, 42 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_geometry_set_instances.hh b/source/blender/blenkernel/BKE_geometry_set_instances.hh
new file mode 100644
index 00000000000..11725d75df9
--- /dev/null
+++ b/source/blender/blenkernel/BKE_geometry_set_instances.hh
@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+
+#include "BKE_geometry_set.hh"
+
+namespace blender::bke {
+
+/**
+ * Used to keep track of a group of instances using the same geometry data.
+ */
+struct GeometryInstanceGroup {
+  /**
+   * The geometry set instanced on each of the transforms. The components are not necessarily
+   * owned here. For example, they may be owned by the instanced object. This cannot be a
+   * reference because not all instanced data will necessarily have a #geometry_set_eval.
+   */
+  GeometrySet geometry_set;
+
+  /**
+   * As an optimization to avoid copying, the same geometry set can be associated with multiple
+   * instances. Each instance is stored as a transform matrix here. Again, these must be owned
+   * because they may be transformed from the original data. TODO: Validate that last statement.
+   */
+  Vector<float4x4> transforms;
+};
+
+Vector<GeometryInstanceGroup> geometry_set_gather_instances(const GeometrySet &geometry_set);
+
+}  // namespace blender::bke