Geometry Nodes: fields and anonymous attributes

This implements the initial core framework for fields and anonymous
attributes (also see T91274).

The new functionality is hidden behind the "Geometry Nodes Fields"
feature flag. When enabled in the user preferences, the following
new nodes become available: `Position`, `Index`, `Normal`,
`Set Position` and `Attribute Capture`.

Socket inspection has not been updated to work with fields yet.

Besides these changes at the user level, this patch contains the
ground work for:
* building and evaluating fields at run-time (`FN_fields.hh`) and
* creating and accessing anonymous attributes on geometry
  (`BKE_anonymous_attribute.h`).

For evaluating fields we use a new so called multi-function procedure
(`FN_multi_function_procedure.hh`). It allows composing multi-functions
in arbitrary ways and supports efficient evaluation as is required by
fields. See `FN_multi_function_procedure.hh` for more details on how
this evaluation mechanism can be used.

A new `AttributeIDRef` has been added which allows handling named
and anonymous attributes in the same way in many places.

Hans and I worked on this patch together.

Differential Revision: https://developer.blender.org/D12414

1 files changed, 260 insertions, 0 deletions

diff --git a/source/blender/functions/FN_multi_function_procedure_builder.hh b/source/blender/functions/FN_multi_function_procedure_builder.hh
new file mode 100644
index 00000000000..d5e45470a0e
--- /dev/null
+++ b/source/blender/functions/FN_multi_function_procedure_builder.hh
@@ -0,0 +1,260 @@
+/*
+ * 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
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_multi_function_procedure.hh"
+
+namespace blender::fn {
+
+/**
+ * An #MFInstructionCursor points to a position in a multi-function procedure, where an instruction
+ * can be inserted.
+ */
+class MFInstructionCursor {
+ private:
+  MFInstruction *instruction_ = nullptr;
+  /* Only used when it is a branch instruction. */
+  bool branch_output_ = false;
+  /* Only used when instruction is null. */
+  bool is_entry_ = false;
+
+ public:
+  MFInstructionCursor() = default;
+
+  MFInstructionCursor(MFCallInstruction &instruction);
+  MFInstructionCursor(MFDestructInstruction &instruction);
+  MFInstructionCursor(MFBranchInstruction &instruction, bool branch_output);
+  MFInstructionCursor(MFDummyInstruction &instruction);
+
+  static MFInstructionCursor Entry();
+
+  void insert(MFProcedure &procedure, MFInstruction *new_instruction);
+};
+
+/**
+ * Utility class to build a #MFProcedure.
+ */
+class MFProcedureBuilder {
+ private:
+  /** Procedure that is being build. */
+  MFProcedure *procedure_ = nullptr;
+  /** Cursors where the next instruction should be inserted. */
+  Vector<MFInstructionCursor> cursors_;
+
+ public:
+  struct Branch;
+  struct Loop;
+
+  MFProcedureBuilder(MFProcedure &procedure,
+                     MFInstructionCursor initial_cursor = MFInstructionCursor::Entry());
+
+  MFProcedureBuilder(Span<MFProcedureBuilder *> builders);
+
+  MFProcedureBuilder(Branch &branch);
+
+  void set_cursor(const MFInstructionCursor &cursor);
+  void set_cursor(Span<MFInstructionCursor> cursors);
+  void set_cursor(Span<MFProcedureBuilder *> builders);
+  void set_cursor_after_branch(Branch &branch);
+  void set_cursor_after_loop(Loop &loop);
+
+  void add_destruct(MFVariable &variable);
+  void add_destruct(Span<MFVariable *> variables);
+
+  MFReturnInstruction &add_return();
+
+  Branch add_branch(MFVariable &condition);
+
+  Loop add_loop();
+  void add_loop_continue(Loop &loop);
+  void add_loop_break(Loop &loop);
+
+  MFCallInstruction &add_call_with_no_variables(const MultiFunction &fn);
+  MFCallInstruction &add_call_with_all_variables(const MultiFunction &fn,
+                                                 Span<MFVariable *> param_variables);
+
+  Vector<MFVariable *> add_call(const MultiFunction &fn,
+                                Span<MFVariable *> input_and_mutable_variables = {});
+
+  template<int OutputN>
+  std::array<MFVariable *, OutputN> add_call(const MultiFunction &fn,
+                                             Span<MFVariable *> input_and_mutable_variables = {});
+
+  void add_parameter(MFParamType::InterfaceType interface_type, MFVariable &variable);
+  MFVariable &add_parameter(MFParamType param_type, std::string name = "");
+
+  MFVariable &add_input_parameter(MFDataType data_type, std::string name = "");
+  template<typename T> MFVariable &add_single_input_parameter(std::string name = "");
+  template<typename T> MFVariable &add_single_mutable_parameter(std::string name = "");
+
+  void add_output_parameter(MFVariable &variable);
+
+ private:
+  void link_to_cursors(MFInstruction *instruction);
+};
+
+struct MFProcedureBuilder::Branch {
+  MFProcedureBuilder branch_true;
+  MFProcedureBuilder branch_false;
+};
+
+struct MFProcedureBuilder::Loop {
+  MFInstruction *begin = nullptr;
+  MFDummyInstruction *end = nullptr;
+};
+
+/* --------------------------------------------------------------------
+ * MFInstructionCursor inline methods.
+ */
+
+inline MFInstructionCursor::MFInstructionCursor(MFCallInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFDestructInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFBranchInstruction &instruction,
+                                                bool branch_output)
+    : instruction_(&instruction), branch_output_(branch_output)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFDummyInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor MFInstructionCursor::Entry()
+{
+  MFInstructionCursor cursor;
+  cursor.is_entry_ = true;
+  return cursor;
+}
+
+/* --------------------------------------------------------------------
+ * MFProcedureBuilder inline methods.
+ */
+
+inline MFProcedureBuilder::MFProcedureBuilder(Branch &branch)
+    : MFProcedureBuilder(*branch.branch_true.procedure_)
+{
+  this->set_cursor_after_branch(branch);
+}
+
+inline MFProcedureBuilder::MFProcedureBuilder(MFProcedure &procedure,
+                                              MFInstructionCursor initial_cursor)
+    : procedure_(&procedure), cursors_({initial_cursor})
+{
+}
+
+inline MFProcedureBuilder::MFProcedureBuilder(Span<MFProcedureBuilder *> builders)
+    : MFProcedureBuilder(*builders[0]->procedure_)
+{
+  this->set_cursor(builders);
+}
+
+inline void MFProcedureBuilder::set_cursor(const MFInstructionCursor &cursor)
+{
+  cursors_ = {cursor};
+}
+
+inline void MFProcedureBuilder::set_cursor(Span<MFInstructionCursor> cursors)
+{
+  cursors_ = cursors;
+}
+
+inline void MFProcedureBuilder::set_cursor_after_branch(Branch &branch)
+{
+  this->set_cursor({&branch.branch_false, &branch.branch_true});
+}
+
+inline void MFProcedureBuilder::set_cursor_after_loop(Loop &loop)
+{
+  this->set_cursor(MFInstructionCursor{*loop.end});
+}
+
+inline void MFProcedureBuilder::set_cursor(Span<MFProcedureBuilder *> builders)
+{
+  cursors_.clear();
+  for (MFProcedureBuilder *builder : builders) {
+    cursors_.extend(builder->cursors_);
+  }
+}
+
+template<int OutputN>
+inline std::array<MFVariable *, OutputN> MFProcedureBuilder::add_call(
+    const MultiFunction &fn, Span<MFVariable *> input_and_mutable_variables)
+{
+  Vector<MFVariable *> output_variables = this->add_call(fn, input_and_mutable_variables);
+  BLI_assert(output_variables.size() == OutputN);
+
+  std::array<MFVariable *, OutputN> output_array;
+  initialized_copy_n(output_variables.data(), OutputN, output_array.data());
+  return output_array;
+}
+
+inline void MFProcedureBuilder::add_parameter(MFParamType::InterfaceType interface_type,
+                                              MFVariable &variable)
+{
+  procedure_->add_parameter(interface_type, variable);
+}
+
+inline MFVariable &MFProcedureBuilder::add_parameter(MFParamType param_type, std::string name)
+{
+  MFVariable &variable = procedure_->new_variable(param_type.data_type(), std::move(name));
+  this->add_parameter(param_type.interface_type(), variable);
+  return variable;
+}
+
+inline MFVariable &MFProcedureBuilder::add_input_parameter(MFDataType data_type, std::string name)
+{
+  return this->add_parameter(MFParamType(MFParamType::Input, data_type), std::move(name));
+}
+
+template<typename T>
+inline MFVariable &MFProcedureBuilder::add_single_input_parameter(std::string name)
+{
+  return this->add_parameter(MFParamType::ForSingleInput(CPPType::get<T>()), std::move(name));
+}
+
+template<typename T>
+inline MFVariable &MFProcedureBuilder::add_single_mutable_parameter(std::string name)
+{
+  return this->add_parameter(MFParamType::ForMutableSingle(CPPType::get<T>()), std::move(name));
+}
+
+inline void MFProcedureBuilder::add_output_parameter(MFVariable &variable)
+{
+  this->add_parameter(MFParamType::Output, variable);
+}
+
+inline void MFProcedureBuilder::link_to_cursors(MFInstruction *instruction)
+{
+  for (MFInstructionCursor &cursor : cursors_) {
+    cursor.insert(*procedure_, instruction);
+  }
+}
+
+}  // namespace blender::fn