Geometry Nodes: Use separate field context for each geometry type

Using the same `GeometryComponentFieldContext` for all situations,
even when only one geometry type is supported is misleading, and mixes
too many different abstraction levels into code that could be simpler.
With the attribute API moved out of geometry components recently,
the "component" system is just getting in the way here.

This commit adds specific field contexts for geometry types: meshes,
curves, point clouds, and instances. There are also separate field input
helper classes, to help reduce boilerplate for fields that only support
specific geometry types.

Another benefit of this change is that it separates geometry components
from fields, which makes it easier to see the purpose of the two concepts,
and how they relate.

Because we want to be able to evaluate a field on just `CurvesGeometry`
rather than the full `Curves` data-block, the generic "geometry context"
had to be changed to avoid using `GeometryComponent`, since there is
no corresponding geometry component type. The resulting void pointer
is ugly, but only turns up in three places in practice. When Apple clang
supports `std::variant`, that could be used instead.

Differential Revision: https://developer.blender.org/D15519

2 files changed, 42 insertions, 56 deletions

diff --git a/source/blender/geometry/GEO_resample_curves.hh b/source/blender/geometry/GEO_resample_curves.hh
index 97399ccb0a5..7ecfb5c26ec 100644
--- a/source/blender/geometry/GEO_resample_curves.hh
+++ b/source/blender/geometry/GEO_resample_curves.hh
@@ -4,12 +4,12 @@
 
 #include "FN_field.hh"
 
-#include "BKE_geometry_set.hh"
-
-struct Curves;
+#include "BKE_curves.hh"
 
 namespace blender::geometry {
 
+using bke::CurvesGeometry;
+
 /**
  * Create new curves where the selected curves have been resampled with a number of uniform-length
  * samples defined by the count field. Interpolate attributes to the result, with an accuracy that
@@ -17,23 +17,23 @@ namespace blender::geometry {
  *
  * \note The values provided by the #count_field are clamped to 1 or greater.
  */
-Curves *resample_to_count(const CurveComponent &src_component,
-                          const fn::Field<bool> &selection_field,
-                          const fn::Field<int> &count_field);
+CurvesGeometry resample_to_count(const CurvesGeometry &src_curves,
+                                 const fn::Field<bool> &selection_field,
+                                 const fn::Field<int> &count_field);
 
 /**
  * Create new curves resampled to make each segment have the length specified by the
  * #segment_length field input, rounded to make the length of each segment the same.
  * The accuracy will depend on the curve's resolution parameter.
  */
-Curves *resample_to_length(const CurveComponent &src_component,
-                           const fn::Field<bool> &selection_field,
-                           const fn::Field<float> &segment_length_field);
+CurvesGeometry resample_to_length(const CurvesGeometry &src_curves,
+                                  const fn::Field<bool> &selection_field,
+                                  const fn::Field<float> &segment_length_field);
 
 /**
  * Evaluate each selected curve to its implicit evaluated points.
  */
-Curves *resample_to_evaluated(const CurveComponent &src_component,
-                              const fn::Field<bool> &selection_field);
+CurvesGeometry resample_to_evaluated(const CurvesGeometry &src_curves,
+                                     const fn::Field<bool> &selection_field);
 
 }  // namespace blender::geometry
diff --git a/source/blender/geometry/intern/resample_curves.cc b/source/blender/geometry/intern/resample_curves.cc
index e4cb99a9eac..d5560a95a18 100644
--- a/source/blender/geometry/intern/resample_curves.cc
+++ b/source/blender/geometry/intern/resample_curves.cc
@@ -88,20 +88,20 @@ static bool interpolate_attribute_to_poly_curve(const bke::AttributeIDRef &attri
  * Retrieve spans from source and result attributes.
  */
 static void retrieve_attribute_spans(const Span<bke::AttributeIDRef> ids,
-                                     const CurveComponent &src_component,
-                                     CurveComponent &dst_component,
+                                     const CurvesGeometry &src_curves,
+                                     CurvesGeometry &dst_curves,
                                      Vector<GSpan> &src,
                                      Vector<GMutableSpan> &dst,
                                      Vector<bke::GSpanAttributeWriter> &dst_attributes)
 {
   for (const int i : ids.index_range()) {
-    GVArray src_attribute = src_component.attributes()->lookup(ids[i], ATTR_DOMAIN_POINT);
+    GVArray src_attribute = src_curves.attributes().lookup(ids[i], ATTR_DOMAIN_POINT);
     BLI_assert(src_attribute);
     src.append(src_attribute.get_internal_span());
 
     const eCustomDataType data_type = bke::cpp_type_to_custom_data_type(src_attribute.type());
     bke::GSpanAttributeWriter dst_attribute =
-        dst_component.attributes_for_write()->lookup_or_add_for_write_only_span(
+        dst_curves.attributes_for_write().lookup_or_add_for_write_only_span(
             ids[i], ATTR_DOMAIN_POINT, data_type);
     dst.append(dst_attribute.span);
     dst_attributes.append(std::move(dst_attribute));
@@ -121,16 +121,13 @@ struct AttributesForInterpolation : NonCopyable, NonMovable {
 /**
  * Gather a set of all generic attribute IDs to copy to the result curves.
  */
-static void gather_point_attributes_to_interpolate(const CurveComponent &src_component,
-                                                   CurveComponent &dst_component,
+static void gather_point_attributes_to_interpolate(const CurvesGeometry &src_curves,
+                                                   CurvesGeometry &dst_curves,
                                                    AttributesForInterpolation &result)
 {
-  bke::CurvesGeometry &dst_curves = bke::CurvesGeometry::wrap(
-      dst_component.get_for_write()->geometry);
-
   VectorSet<bke::AttributeIDRef> ids;
   VectorSet<bke::AttributeIDRef> ids_no_interpolation;
-  src_component.attributes()->for_all(
+  src_curves.attributes().for_all(
       [&](const bke::AttributeIDRef &id, const bke::AttributeMetaData meta_data) {
         if (meta_data.domain != ATTR_DOMAIN_POINT) {
           return true;
@@ -152,29 +149,25 @@ static void gather_point_attributes_to_interpolate(const CurveComponent &src_com
   ids.remove_contained("position");
 
   retrieve_attribute_spans(
-      ids, src_component, dst_component, result.src, result.dst, result.dst_attributes);
+      ids, src_curves, dst_curves, result.src, result.dst, result.dst_attributes);
 
   /* Attributes that aren't interpolated like Bezier handles still have to be copied
    * to the result when there are any unselected curves of the corresponding type. */
   retrieve_attribute_spans(ids_no_interpolation,
-                           src_component,
-                           dst_component,
+                           src_curves,
+                           dst_curves,
                            result.src_no_interpolation,
                            result.dst_no_interpolation,
                            result.dst_attributes);
 }
 
-static Curves *resample_to_uniform(const CurveComponent &src_component,
-                                   const fn::Field<bool> &selection_field,
-                                   const fn::Field<int> &count_field)
+static CurvesGeometry resample_to_uniform(const CurvesGeometry &src_curves,
+                                          const fn::Field<bool> &selection_field,
+                                          const fn::Field<int> &count_field)
 {
-  const bke::CurvesGeometry &src_curves = bke::CurvesGeometry::wrap(
-      src_component.get_for_read()->geometry);
-
   /* Create the new curves without any points and evaluate the final count directly
    * into the offsets array, in order to be accumulated into offsets later. */
-  Curves *dst_curves_id = bke::curves_new_nomain(0, src_curves.curves_num());
-  bke::CurvesGeometry &dst_curves = bke::CurvesGeometry::wrap(dst_curves_id->geometry);
+  CurvesGeometry dst_curves = CurvesGeometry(0, src_curves.curves_num());
 
   /* Directly copy curve attributes, since they stay the same (except for curve types). */
   CustomData_copy(&src_curves.curve_data,
@@ -184,7 +177,7 @@ static Curves *resample_to_uniform(const CurveComponent &src_component,
                   src_curves.curves_num());
   MutableSpan<int> dst_offsets = dst_curves.offsets_for_write();
 
-  bke::GeometryComponentFieldContext field_context{src_component, ATTR_DOMAIN_CURVE};
+  bke::CurvesFieldContext field_context{src_curves, ATTR_DOMAIN_CURVE};
   fn::FieldEvaluator evaluator{field_context, src_curves.curves_num()};
   evaluator.set_selection(selection_field);
   evaluator.add_with_destination(count_field, dst_offsets);
@@ -207,9 +200,7 @@ static Curves *resample_to_uniform(const CurveComponent &src_component,
   MutableSpan<float3> dst_positions = dst_curves.positions_for_write();
 
   AttributesForInterpolation attributes;
-  CurveComponent dst_component;
-  dst_component.replace(dst_curves_id, GeometryOwnershipType::Editable);
-  gather_point_attributes_to_interpolate(src_component, dst_component, attributes);
+  gather_point_attributes_to_interpolate(src_curves, dst_curves, attributes);
 
   src_curves.ensure_evaluated_lengths();
 
@@ -322,32 +313,30 @@ static Curves *resample_to_uniform(const CurveComponent &src_component,
     attribute.finish();
   }
 
-  return dst_curves_id;
+  return dst_curves;
 }
 
-Curves *resample_to_count(const CurveComponent &src_component,
-                          const fn::Field<bool> &selection_field,
-                          const fn::Field<int> &count_field)
+CurvesGeometry resample_to_count(const CurvesGeometry &src_curves,
+                                 const fn::Field<bool> &selection_field,
+                                 const fn::Field<int> &count_field)
 {
-  return resample_to_uniform(src_component, selection_field, get_count_input_max_one(count_field));
+  return resample_to_uniform(src_curves, selection_field, get_count_input_max_one(count_field));
 }
 
-Curves *resample_to_length(const CurveComponent &src_component,
-                           const fn::Field<bool> &selection_field,
-                           const fn::Field<float> &segment_length_field)
+CurvesGeometry resample_to_length(const CurvesGeometry &src_curves,
+                                  const fn::Field<bool> &selection_field,
+                                  const fn::Field<float> &segment_length_field)
 {
   return resample_to_uniform(
-      src_component, selection_field, get_count_input_from_length(segment_length_field));
+      src_curves, selection_field, get_count_input_from_length(segment_length_field));
 }
 
-Curves *resample_to_evaluated(const CurveComponent &src_component,
-                              const fn::Field<bool> &selection_field)
+CurvesGeometry resample_to_evaluated(const CurvesGeometry &src_curves,
+                                     const fn::Field<bool> &selection_field)
 {
-  const bke::CurvesGeometry &src_curves = bke::CurvesGeometry::wrap(
-      src_component.get_for_read()->geometry);
   src_curves.ensure_evaluated_offsets();
 
-  bke::GeometryComponentFieldContext field_context{src_component, ATTR_DOMAIN_CURVE};
+  bke::CurvesFieldContext field_context{src_curves, ATTR_DOMAIN_CURVE};
   fn::FieldEvaluator evaluator{field_context, src_curves.curves_num()};
   evaluator.set_selection(selection_field);
   evaluator.evaluate();
@@ -355,8 +344,7 @@ Curves *resample_to_evaluated(const CurveComponent &src_component,
   const Vector<IndexRange> unselected_ranges = selection.extract_ranges_invert(
       src_curves.curves_range(), nullptr);
 
-  Curves *dst_curves_id = bke::curves_new_nomain(0, src_curves.curves_num());
-  bke::CurvesGeometry &dst_curves = bke::CurvesGeometry::wrap(dst_curves_id->geometry);
+  CurvesGeometry dst_curves(0, src_curves.curves_num());
 
   /* Directly copy curve attributes, since they stay the same (except for curve types). */
   CustomData_copy(&src_curves.curve_data,
@@ -384,9 +372,7 @@ Curves *resample_to_evaluated(const CurveComponent &src_component,
   MutableSpan<float3> dst_positions = dst_curves.positions_for_write();
 
   AttributesForInterpolation attributes;
-  CurveComponent dst_component;
-  dst_component.replace(dst_curves_id, GeometryOwnershipType::Editable);
-  gather_point_attributes_to_interpolate(src_component, dst_component, attributes);
+  gather_point_attributes_to_interpolate(src_curves, dst_curves, attributes);
 
   threading::parallel_for(selection.index_range(), 512, [&](IndexRange selection_range) {
     const IndexMask sliced_selection = selection.slice(selection_range);
@@ -445,7 +431,7 @@ Curves *resample_to_evaluated(const CurveComponent &src_component,
     attribute.finish();
   }
 
-  return dst_curves_id;
+  return dst_curves;
 }
 
 }  // namespace blender::geometry