Geometry Nodes: Initial basic curve data support

This patch adds initial curve support to geometry nodes. Currently
there is only one node available, the "Curve to Mesh" node, T87428.

However, the aim of the changes here is larger than just supporting
curve data in nodes-- it also uses the opportunity to add better spline
data structures, intended to replace the existing curve evaluation code.
The curve code in Blender is quite old, and it's generally regarded as
some of the messiest, hardest-to-understand code as well. The classes
in `BKE_spline.hh` aim to be faster, more extensible, and much more
easily understandable. Further explanation can be found in comments in
that file.

Initial builtin spline attributes are supported-- reading and writing
from the `cyclic` and `resolution` attributes works with any of the
attribute nodes. Also, only Z-up normal calculation is implemented
at the moment, and tilts do not apply yet.

**Limitations**
 - For now, you must bring curves into the node tree with an "Object
   Info" node. Changes to the curve modifier stack will come later.
 - Converting to a mesh is necessary to visualize the curve data.

Further progress can be tracked in: T87245
Higher level design document: https://wiki.blender.org/wiki/Modules/Physics_Nodes/Projects/EverythingNodes/CurveNodes

Differential Revision: https://developer.blender.org/D11091

1 files changed, 45 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/geometry_set.cc b/source/blender/blenkernel/intern/geometry_set.cc
index 6ae78343fea..3d85118deee 100644
--- a/source/blender/blenkernel/intern/geometry_set.cc
+++ b/source/blender/blenkernel/intern/geometry_set.cc
@@ -24,6 +24,7 @@
 #include "BKE_mesh_wrapper.h"
 #include "BKE_modifier.h"
 #include "BKE_pointcloud.h"
+#include "BKE_spline.hh"
 #include "BKE_volume.h"
 
 #include "DNA_collection_types.h"
@@ -60,6 +61,8 @@ GeometryComponent *GeometryComponent::create(GeometryComponentType component_typ
       return new InstancesComponent();
     case GEO_COMPONENT_TYPE_VOLUME:
       return new VolumeComponent();
+    case GEO_COMPONENT_TYPE_CURVE:
+      return new CurveComponent();
   }
   BLI_assert_unreachable();
   return nullptr;
@@ -182,6 +185,11 @@ void GeometrySet::compute_boundbox_without_instances(float3 *r_min, float3 *r_ma
   if (volume != nullptr) {
     BKE_volume_min_max(volume, *r_min, *r_max);
   }
+  const CurveEval *curve = this->get_curve_for_read();
+  if (curve != nullptr) {
+    /* Using the evaluated positions is somewhat arbitrary, but it is probably expected. */
+    curve->bounds_min_max(*r_min, *r_max, true);
+  }
 }
 
 std::ostream &operator<<(std::ostream &stream, const GeometrySet &geometry_set)
@@ -252,6 +260,13 @@ const Volume *GeometrySet::get_volume_for_read() const
   return (component == nullptr) ? nullptr : component->get_for_read();
 }
 
+/* Returns a read-only curve or null. */
+const CurveEval *GeometrySet::get_curve_for_read() const
+{
+  const CurveComponent *component = this->get_component_for_read<CurveComponent>();
+  return (component == nullptr) ? nullptr : component->get_for_read();
+}
+
 /* Returns true when the geometry set has a point cloud component that has a point cloud. */
 bool GeometrySet::has_pointcloud() const
 {
@@ -273,6 +288,13 @@ bool GeometrySet::has_volume() const
   return component != nullptr && component->has_volume();
 }
 
+/* Returns true when the geometry set has a curve component that has a curve. */
+bool GeometrySet::has_curve() const
+{
+  const CurveComponent *component = this->get_component_for_read<CurveComponent>();
+  return component != nullptr && component->has_curve();
+}
+
 /* Create a new geometry set that only contains the given mesh. */
 GeometrySet GeometrySet::create_with_mesh(Mesh *mesh, GeometryOwnershipType ownership)
 {
@@ -292,6 +314,15 @@ GeometrySet GeometrySet::create_with_pointcloud(PointCloud *pointcloud,
   return geometry_set;
 }
 
+/* Create a new geometry set that only contains the given curve. */
+GeometrySet GeometrySet::create_with_curve(CurveEval *curve, GeometryOwnershipType ownership)
+{
+  GeometrySet geometry_set;
+  CurveComponent &component = geometry_set.get_component_for_write<CurveComponent>();
+  component.replace(curve, ownership);
+  return geometry_set;
+}
+
 /* Clear the existing mesh and replace it with the given one. */
 void GeometrySet::replace_mesh(Mesh *mesh, GeometryOwnershipType ownership)
 {
@@ -299,6 +330,13 @@ void GeometrySet::replace_mesh(Mesh *mesh, GeometryOwnershipType ownership)
   component.replace(mesh, ownership);
 }
 
+/* Clear the existing curve and replace it with the given one. */
+void GeometrySet::replace_curve(CurveEval *curve, GeometryOwnershipType ownership)
+{
+  CurveComponent &component = this->get_component_for_write<CurveComponent>();
+  component.replace(curve, ownership);
+}
+
 /* Clear the existing point cloud and replace with the given one. */
 void GeometrySet::replace_pointcloud(PointCloud *pointcloud, GeometryOwnershipType ownership)
 {
@@ -334,6 +372,13 @@ Volume *GeometrySet::get_volume_for_write()
   return component.get_for_write();
 }
 
+/* Returns a mutable curve or null. No ownership is transferred. */
+CurveEval *GeometrySet::get_curve_for_write()
+{
+  CurveComponent &component = this->get_component_for_write<CurveComponent>();
+  return component.get_for_write();
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */