Geometry Nodes: Support instances in the delete geometry node

Ever since the instance domain was added, this was exposed, it just
didn't do anything. This patch implements the instances domain in the
delete and separate geometry nodes, where it acts on the top-level
instances.

We act on a mutable instances input, with the idea that eventually
copy on write attribute layers will make this less expensive. It also
allows us to keep the instance references in place and to do less
work in some situations.

Ref T93554

Differential Revision: https://developer.blender.org/D13565

1 files changed, 31 insertions, 1 deletions

diff --git a/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc b/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
index a5197b23adb..7d41242b8bc 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
@@ -529,6 +529,30 @@ static void separate_point_cloud_selection(GeometrySet &geometry_set,
   geometry_set.replace_pointcloud(pointcloud);
 }
 
+static void separate_instance_selection(GeometrySet &geometry_set,
+                                        const Field<bool> &selection_field,
+                                        const bool invert)
+{
+  InstancesComponent &instances = geometry_set.get_component_for_write<InstancesComponent>();
+  GeometryComponentFieldContext field_context{instances, ATTR_DOMAIN_INSTANCE};
+
+  const int domain_size = instances.attribute_domain_size(ATTR_DOMAIN_INSTANCE);
+  fn::FieldEvaluator evaluator{field_context, domain_size};
+  evaluator.add(selection_field);
+  evaluator.evaluate();
+  const VArray_Span<bool> &selection = evaluator.get_evaluated<bool>(0);
+
+  Vector<int64_t> indices;
+  const IndexMask mask = index_mask_indices(selection, invert, indices);
+
+  if (mask.size() == 0) {
+    geometry_set.remove<InstancesComponent>();
+    return;
+  }
+
+  instances.remove_instances(mask);
+}
+
 static void compute_selected_vertices_from_vertex_selection(const Span<bool> vertex_selection,
                                                             const bool invert,
                                                             MutableSpan<int> r_vertex_map,
@@ -1261,7 +1285,7 @@ void separate_geometry(GeometrySet &geometry_set,
     }
   }
   if (geometry_set.has_mesh()) {
-    if (domain != ATTR_DOMAIN_CURVE) {
+    if (ELEM(domain, ATTR_DOMAIN_POINT, ATTR_DOMAIN_EDGE, ATTR_DOMAIN_FACE, ATTR_DOMAIN_CORNER)) {
       separate_mesh_selection(geometry_set, selection_field, domain, mode, invert);
       some_valid_domain = true;
     }
@@ -1272,6 +1296,12 @@ void separate_geometry(GeometrySet &geometry_set,
       some_valid_domain = true;
     }
   }
+  if (geometry_set.has_instances()) {
+    if (domain == ATTR_DOMAIN_INSTANCE) {
+      separate_instance_selection(geometry_set, selection_field, invert);
+      some_valid_domain = true;
+    }
+  }
   r_is_error = !some_valid_domain && geometry_set.has_realized_data();
 }