Geometry Nodes: add field node type for constants

It is common to have fields that contain a constant value. Before this
commit, such constants were represented by operation nodes which
don't have inputs. Having a special node type for constants makes
working with them a bit cheaper.

It also allows skipping some unnecessary processing when evaluating
fields, because constant fields can be detected more easily.

This commit also generalizes the concept of field node types a bit.

1 files changed, 12 insertions, 1 deletions

diff --git a/source/blender/functions/FN_multi_function_procedure.hh b/source/blender/functions/FN_multi_function_procedure.hh
index a26eb1045a7..d73bc089278 100644
--- a/source/blender/functions/FN_multi_function_procedure.hh
+++ b/source/blender/functions/FN_multi_function_procedure.hh
@@ -268,6 +268,7 @@ class MFProcedure : NonCopyable, NonMovable {
   Vector<MFReturnInstruction *> return_instructions_;
   Vector<MFVariable *> variables_;
   Vector<MFParameter> params_;
+  Vector<destruct_ptr<MultiFunction>> owned_functions_;
   MFInstruction *entry_ = nullptr;
 
   friend class MFProcedureDotExport;
@@ -284,9 +285,10 @@ class MFProcedure : NonCopyable, NonMovable {
   MFReturnInstruction &new_return_instruction();
 
   void add_parameter(MFParamType::InterfaceType interface_type, MFVariable &variable);
-
   Span<ConstMFParameter> params() const;
 
+  template<typename T, typename... Args> const MultiFunction &construct_function(Args &&...args);
+
   MFInstruction *entry();
   const MFInstruction *entry() const;
   void set_entry(MFInstruction &entry);
@@ -550,6 +552,15 @@ inline Span<const MFVariable *> MFProcedure::variables() const
   return variables_;
 }
 
+template<typename T, typename... Args>
+inline const MultiFunction &MFProcedure::construct_function(Args &&...args)
+{
+  destruct_ptr<T> fn = allocator_.construct<T>(std::forward<Args>(args)...);
+  const MultiFunction &fn_ref = *fn;
+  owned_functions_.append(std::move(fn));
+  return fn_ref;
+}
+
 /** \} */
 
 }  // namespace blender::fn