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, 155 insertions, 0 deletions

diff --git a/source/blender/nodes/NOD_geometry_exec.hh b/source/blender/nodes/NOD_geometry_exec.hh
new file mode 100644
index 00000000000..2b95f76d06b
--- /dev/null
+++ b/source/blender/nodes/NOD_geometry_exec.hh
@@ -0,0 +1,155 @@
+/*
+ * 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 "FN_generic_value_map.hh"
+
+#include "BKE_attribute_access.hh"
+#include "BKE_geometry_set.hh"
+#include "BKE_persistent_data_handle.hh"
+
+#include "DNA_node_types.h"
+
+namespace blender::nodes {
+
+using bke::Float3ReadAttribute;
+using bke::Float3WriteAttribute;
+using bke::FloatReadAttribute;
+using bke::FloatWriteAttribute;
+using bke::PersistentDataHandleMap;
+using bke::PersistentObjectHandle;
+using bke::ReadAttribute;
+using bke::ReadAttributePtr;
+using bke::WriteAttribute;
+using bke::WriteAttributePtr;
+using fn::CPPType;
+using fn::GMutablePointer;
+using fn::GValueMap;
+
+class GeoNodeExecParams {
+ private:
+  const bNode &node_;
+  GValueMap<StringRef> &input_values_;
+  GValueMap<StringRef> &output_values_;
+  const PersistentDataHandleMap &handle_map_;
+  const Object *self_object_;
+
+ public:
+  GeoNodeExecParams(const bNode &node,
+                    GValueMap<StringRef> &input_values,
+                    GValueMap<StringRef> &output_values,
+                    const PersistentDataHandleMap &handle_map,
+                    const Object *self_object)
+      : node_(node),
+        input_values_(input_values),
+        output_values_(output_values),
+        handle_map_(handle_map),
+        self_object_(self_object)
+  {
+  }
+
+  /**
+   * Get the input value for the input socket with the given identifier.
+   *
+   * The node calling becomes responsible for destructing the value before it is done
+   * executing. This method can only be called once for each identifier.
+   */
+  GMutablePointer extract_input(StringRef identifier)
+  {
+#ifdef DEBUG
+    this->check_extract_input(identifier);
+#endif
+    return input_values_.extract(identifier);
+  }
+
+  /**
+   * Get the input value for the input socket with the given identifier.
+   *
+   * This method can only be called once for each identifier.
+   */
+  template<typename T> T extract_input(StringRef identifier)
+  {
+#ifdef DEBUG
+    this->check_extract_input(identifier, &CPPType::get<T>());
+#endif
+    return input_values_.extract<T>(identifier);
+  }
+
+  /**
+   * Get the input value for the input socket with the given identifier.
+   *
+   * This makes a copy of the value, which is fine for most types but should be avoided for
+   * geometry sets.
+   */
+  template<typename T> T get_input(StringRef identifier) const
+  {
+#ifdef DEBUG
+    this->check_extract_input(identifier, &CPPType::get<T>());
+#endif
+    return input_values_.lookup<T>(identifier);
+  }
+
+  /**
+   * Move-construct a new value based on the given value and store it for the given socket
+   * identifier.
+   */
+  void set_output_by_move(StringRef identifier, GMutablePointer value)
+  {
+#ifdef DEBUG
+    BLI_assert(value.type() != nullptr);
+    BLI_assert(value.get() != nullptr);
+    this->check_set_output(identifier, *value.type());
+#endif
+    output_values_.add_new_by_move(identifier, value);
+  }
+
+  /**
+   * Store the output value for the given socket identifier.
+   */
+  template<typename T> void set_output(StringRef identifier, T &&value)
+  {
+#ifdef DEBUG
+    this->check_set_output(identifier, CPPType::get<std::decay_t<T>>());
+#endif
+    output_values_.add_new(identifier, std::forward<T>(value));
+  }
+
+  /**
+   * Get the node that is currently being executed.
+   */
+  const bNode &node() const
+  {
+    return node_;
+  }
+
+  const PersistentDataHandleMap &handle_map() const
+  {
+    return handle_map_;
+  }
+
+  const Object *self_object() const
+  {
+    return self_object_;
+  }
+
+ private:
+  /* Utilities for detecting common errors at when using this class. */
+  void check_extract_input(StringRef identifier, const CPPType *requested_type = nullptr) const;
+  void check_set_output(StringRef identifier, const CPPType &value_type) const;
+};
+
+}  // namespace blender::nodes