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, 93 insertions, 21 deletions

diff --git a/source/blender/blenkernel/BKE_geometry_set.hh b/source/blender/blenkernel/BKE_geometry_set.hh
index 08b6cb951a8..c3d594d7dcd 100644
--- a/source/blender/blenkernel/BKE_geometry_set.hh
+++ b/source/blender/blenkernel/BKE_geometry_set.hh
@@ -31,9 +31,12 @@
 #include "BLI_user_counter.hh"
 #include "BLI_vector_set.hh"
 
+#include "BKE_anonymous_attribute.hh"
 #include "BKE_attribute_access.hh"
 #include "BKE_geometry_set.h"
 
+#include "FN_field.hh"
+
 struct Collection;
 struct Curve;
 struct CurveEval;
@@ -88,11 +91,11 @@ class GeometryComponent {
   GeometryComponentType type() const;
 
   /* Return true when any attribute with this name exists, including built in attributes. */
-  bool attribute_exists(const blender::StringRef attribute_name) const;
+  bool attribute_exists(const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Return the data type and domain of an attribute with the given name if it exists. */
   std::optional<AttributeMetaData> attribute_get_meta_data(
-      const blender::StringRef attribute_name) const;
+      const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Returns true when the geometry component supports this attribute domain. */
   bool attribute_domain_supported(const AttributeDomain domain) const;
@@ -104,12 +107,12 @@ class GeometryComponent {
   /* Get read-only access to the highest priority attribute with the given name.
    * Returns null if the attribute does not exist. */
   blender::bke::ReadAttributeLookup attribute_try_get_for_read(
-      const blender::StringRef attribute_name) const;
+      const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Get read and write access to the highest priority attribute with the given name.
    * Returns null if the attribute does not exist. */
   blender::bke::WriteAttributeLookup attribute_try_get_for_write(
-      const blender::StringRef attribute_name);
+      const blender::bke::AttributeIDRef &attribute_id);
 
   /* Get a read-only attribute for the domain based on the given attribute. This can be used to
    * interpolate from one domain to another.
@@ -120,10 +123,10 @@ class GeometryComponent {
       const AttributeDomain to_domain) const;
 
   /* Returns true when the attribute has been deleted. */
-  bool attribute_try_delete(const blender::StringRef attribute_name);
+  bool attribute_try_delete(const blender::bke::AttributeIDRef &attribute_id);
 
   /* Returns true when the attribute has been created. */
-  bool attribute_try_create(const blender::StringRef attribute_name,
+  bool attribute_try_create(const blender::bke::AttributeIDRef &attribute_id,
                             const AttributeDomain domain,
                             const CustomDataType data_type,
                             const AttributeInit &initializer);
@@ -133,7 +136,7 @@ class GeometryComponent {
   bool attribute_try_create_builtin(const blender::StringRef attribute_name,
                                     const AttributeInit &initializer);
 
-  blender::Set<std::string> attribute_names() const;
+  blender::Set<blender::bke::AttributeIDRef> attribute_ids() const;
   bool attribute_foreach(const AttributeForeachCallback callback) const;
 
   virtual bool is_empty() const;
@@ -142,7 +145,7 @@ class GeometryComponent {
    * Returns null when the attribute does not exist or cannot be converted to the requested domain
    * and data type. */
   std::unique_ptr<blender::fn::GVArray> attribute_try_get_for_read(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type) const;
 
@@ -150,18 +153,18 @@ class GeometryComponent {
    * left unchanged. Returns null when the attribute does not exist or cannot be adapted to the
    * requested domain. */
   std::unique_ptr<blender::fn::GVArray> attribute_try_get_for_read(
-      const blender::StringRef attribute_name, const AttributeDomain domain) const;
+      const blender::bke::AttributeIDRef &attribute_id, const AttributeDomain domain) const;
 
   /* Get a virtual array to read data of an attribute with the given data type. The domain is
    * left unchanged. Returns null when the attribute does not exist or cannot be converted to the
    * requested data type. */
   blender::bke::ReadAttributeLookup attribute_try_get_for_read(
-      const blender::StringRef attribute_name, const CustomDataType data_type) const;
+      const blender::bke::AttributeIDRef &attribute_id, const CustomDataType data_type) const;
 
   /* Get a virtual array to read the data of an attribute. If that is not possible, the returned
    * virtual array will contain a default value. This never returns null. */
   std::unique_ptr<blender::fn::GVArray> attribute_get_for_read(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type,
       const void *default_value = nullptr) const;
@@ -169,14 +172,15 @@ class GeometryComponent {
   /* Should be used instead of the method above when the requested data type is known at compile
    * time for better type safety. */
   template<typename T>
-  blender::fn::GVArray_Typed<T> attribute_get_for_read(const blender::StringRef attribute_name,
-                                                       const AttributeDomain domain,
-                                                       const T &default_value) const
+  blender::fn::GVArray_Typed<T> attribute_get_for_read(
+      const blender::bke::AttributeIDRef &attribute_id,
+      const AttributeDomain domain,
+      const T &default_value) const
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
     std::unique_ptr varray = this->attribute_get_for_read(
-        attribute_name, domain, type, &default_value);
+        attribute_id, domain, type, &default_value);
     return blender::fn::GVArray_Typed<T>(std::move(varray));
   }
 
@@ -191,7 +195,7 @@ class GeometryComponent {
    *   is created that will overwrite the existing attribute in the end.
    */
   blender::bke::OutputAttribute attribute_try_get_for_output(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type,
       const void *default_value = nullptr);
@@ -200,28 +204,30 @@ class GeometryComponent {
    * attributes are not read, i.e. the attribute is used only for output. Since values are not read
    * from this attribute, no default value is necessary. */
   blender::bke::OutputAttribute attribute_try_get_for_output_only(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type);
 
   /* Statically typed method corresponding to the equally named generic one. */
   template<typename T>
   blender::bke::OutputAttribute_Typed<T> attribute_try_get_for_output(
-      const blender::StringRef attribute_name, const AttributeDomain domain, const T default_value)
+      const blender::bke::AttributeIDRef &attribute_id,
+      const AttributeDomain domain,
+      const T default_value)
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType data_type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
-    return this->attribute_try_get_for_output(attribute_name, domain, data_type, &default_value);
+    return this->attribute_try_get_for_output(attribute_id, domain, data_type, &default_value);
   }
 
   /* Statically typed method corresponding to the equally named generic one. */
   template<typename T>
   blender::bke::OutputAttribute_Typed<T> attribute_try_get_for_output_only(
-      const blender::StringRef attribute_name, const AttributeDomain domain)
+      const blender::bke::AttributeIDRef &attribute_id, const AttributeDomain domain)
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType data_type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
-    return this->attribute_try_get_for_output_only(attribute_name, domain, data_type);
+    return this->attribute_try_get_for_output_only(attribute_id, domain, data_type);
   }
 
  private:
@@ -616,3 +622,69 @@ class VolumeComponent : public GeometryComponent {
 
   static constexpr inline GeometryComponentType static_type = GEO_COMPONENT_TYPE_VOLUME;
 };
+
+namespace blender::bke {
+
+class GeometryComponentFieldContext : public fn::FieldContext {
+ private:
+  const GeometryComponent &component_;
+  const AttributeDomain domain_;
+
+ public:
+  GeometryComponentFieldContext(const GeometryComponent &component, const AttributeDomain domain)
+      : component_(component), domain_(domain)
+  {
+  }
+
+  const GeometryComponent &geometry_component() const
+  {
+    return component_;
+  }
+
+  AttributeDomain domain() const
+  {
+    return domain_;
+  }
+};
+
+class AttributeFieldInput : public fn::FieldInput {
+ private:
+  std::string name_;
+
+ public:
+  AttributeFieldInput(std::string name, const CPPType &type)
+      : fn::FieldInput(type, name), name_(std::move(name))
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask mask,
+                                        ResourceScope &scope) const override;
+
+  uint64_t hash() const override;
+  bool is_equal_to(const fn::FieldNode &other) const override;
+};
+
+class AnonymousAttributeFieldInput : public fn::FieldInput {
+ private:
+  /**
+   * A strong reference is required to make sure that the referenced attribute is not removed
+   * automatically.
+   */
+  StrongAnonymousAttributeID anonymous_id_;
+
+ public:
+  AnonymousAttributeFieldInput(StrongAnonymousAttributeID anonymous_id, const CPPType &type)
+      : fn::FieldInput(type, anonymous_id.debug_name()), anonymous_id_(std::move(anonymous_id))
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask mask,
+                                        ResourceScope &scope) const override;
+
+  uint64_t hash() const override;
+  bool is_equal_to(const fn::FieldNode &other) const override;
+};
+
+}  // namespace blender::bke