Geometry Nodes: initial scattering and geometry nodes

This is the initial merge from the geometry-nodes branch.
Nodes:
* Attribute Math
* Boolean
* Edge Split
* Float Compare
* Object Info
* Point Distribute
* Point Instance
* Random Attribute
* Random Float
* Subdivision Surface
* Transform
* Triangulate

It includes the initial evaluation of geometry node groups in the Geometry Nodes modifier.

Notes on the Generic attribute access API

The API adds an indirection for attribute access. That has the following benefits:
* Most code does not have to care about how an attribute is stored internally.
  This is mainly necessary, because we have to deal with "legacy" attributes
  such as vertex weights and attributes that are embedded into other structs
  such as vertex positions.
* When reading from an attribute, we generally don't care what domain the
  attribute is stored on. So we want to abstract away the interpolation that
  that adapts attributes from one domain to another domain (this is not
  actually implemented yet).

Other possible improvements for later iterations include:
* Actually implement interpolation between domains.
* Don't use inheritance for the different attribute types. A single class for read
  access and one for write access might be enough, because we know all the ways
  in which attributes are stored internally. We don't want more different internal
  structures in the future. On the contrary, ideally we can consolidate the different
  storage formats in the future to reduce the need for this indirection.
* Remove the need for heap allocations when creating attribute accessors.

It includes commits from:
* Dalai Felinto
* Hans Goudey
* Jacques Lucke
* Léo Depoix

1 files changed, 36 insertions, 0 deletions

diff --git a/source/blender/nodes/NOD_type_callbacks.hh b/source/blender/nodes/NOD_type_callbacks.hh
new file mode 100644
index 00000000000..d1a4bd3ad7a
--- /dev/null
+++ b/source/blender/nodes/NOD_type_callbacks.hh
@@ -0,0 +1,36 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <optional>
+
+#include "BKE_node.h"
+
+#include "FN_multi_function_data_type.hh"
+
+namespace blender::nodes {
+
+using fn::CPPType;
+using fn::MFDataType;
+
+const CPPType *socket_cpp_type_get(const bNodeSocketType &stype);
+std::optional<MFDataType> socket_mf_type_get(const bNodeSocketType &stype);
+bool socket_is_mf_data_socket(const bNodeSocketType &stype);
+bool socket_cpp_value_get(const bNodeSocket &socket, void *r_value);
+void socket_expand_in_mf_network(SocketMFNetworkBuilder &builder);
+
+}  // namespace blender::nodes