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

1 files changed, 23 insertions, 18 deletions

diff --git a/source/blender/nodes/geometry/nodes/node_geo_curve_resample.cc b/source/blender/nodes/geometry/nodes/node_geo_curve_resample.cc
index 37fc6823b9a..41eafe2a741 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_curve_resample.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_curve_resample.cc
@@ -66,12 +66,14 @@ static void node_geo_exec(GeoNodeExecParams params)
     case GEO_NODE_CURVE_RESAMPLE_COUNT: {
       Field<int> count = params.extract_input<Field<int>>("Count");
       geometry_set.modify_geometry_sets([&](GeometrySet &geometry) {
-        if (const CurveComponent *component = geometry.get_component_for_read<CurveComponent>()) {
-          if (const Curves *src_curves = component->get_for_read()) {
-            Curves *dst_curves = geometry::resample_to_count(*component, selection, count);
-            bke::curves_copy_parameters(*src_curves, *dst_curves);
-            geometry.replace_curves(dst_curves);
-          }
+        if (const Curves *src_curves_id = geometry.get_curves_for_read()) {
+          const bke::CurvesGeometry &src_curves = bke::CurvesGeometry::wrap(
+              src_curves_id->geometry);
+          bke::CurvesGeometry dst_curves = geometry::resample_to_count(
+              src_curves, selection, count);
+          Curves *dst_curves_id = bke::curves_new_nomain(std::move(dst_curves));
+          bke::curves_copy_parameters(*src_curves_id, *dst_curves_id);
+          geometry.replace_curves(dst_curves_id);
         }
       });
       break;
@@ -79,24 +81,27 @@ static void node_geo_exec(GeoNodeExecParams params)
     case GEO_NODE_CURVE_RESAMPLE_LENGTH: {
       Field<float> length = params.extract_input<Field<float>>("Length");
       geometry_set.modify_geometry_sets([&](GeometrySet &geometry) {
-        if (const CurveComponent *component = geometry.get_component_for_read<CurveComponent>()) {
-          if (const Curves *src_curves = component->get_for_read()) {
-            Curves *dst_curves = geometry::resample_to_length(*component, selection, length);
-            bke::curves_copy_parameters(*src_curves, *dst_curves);
-            geometry.replace_curves(dst_curves);
-          }
+        if (const Curves *src_curves_id = geometry.get_curves_for_read()) {
+          const bke::CurvesGeometry &src_curves = bke::CurvesGeometry::wrap(
+              src_curves_id->geometry);
+          bke::CurvesGeometry dst_curves = geometry::resample_to_length(
+              src_curves, selection, length);
+          Curves *dst_curves_id = bke::curves_new_nomain(std::move(dst_curves));
+          bke::curves_copy_parameters(*src_curves_id, *dst_curves_id);
+          geometry.replace_curves(dst_curves_id);
         }
       });
       break;
     }
     case GEO_NODE_CURVE_RESAMPLE_EVALUATED:
       geometry_set.modify_geometry_sets([&](GeometrySet &geometry) {
-        if (const CurveComponent *component = geometry.get_component_for_read<CurveComponent>()) {
-          if (const Curves *src_curves = component->get_for_read()) {
-            Curves *dst_curves = geometry::resample_to_evaluated(*component, selection);
-            bke::curves_copy_parameters(*src_curves, *dst_curves);
-            geometry.replace_curves(dst_curves);
-          }
+        if (const Curves *src_curves_id = geometry.get_curves_for_read()) {
+          const bke::CurvesGeometry &src_curves = bke::CurvesGeometry::wrap(
+              src_curves_id->geometry);
+          bke::CurvesGeometry dst_curves = geometry::resample_to_evaluated(src_curves, selection);
+          Curves *dst_curves_id = bke::curves_new_nomain(std::move(dst_curves));
+          bke::curves_copy_parameters(*src_curves_id, *dst_curves_id);
+          geometry.replace_curves(dst_curves_id);
         }
       });
       break;