Curves: support sculpting on deformed curves

Previously, curves sculpt tools only worked on original data. This was
very limiting, because one could effectively only sculpt the curves when
all procedural effects were turned off. This patch adds support for curves
sculpting while looking the result of procedural effects (like deformation
based on the surface mesh). This functionality is also known as "crazy space"
support in Blender.

For more details see D15407.

Differential Revision: https://developer.blender.org/D15407

1 files changed, 64 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/crazyspace.cc b/source/blender/blenkernel/intern/crazyspace.cc
index c3db3095343..978606ef1fa 100644
--- a/source/blender/blenkernel/intern/crazyspace.cc
+++ b/source/blender/blenkernel/intern/crazyspace.cc
@@ -19,7 +19,10 @@
 
 #include "BKE_DerivedMesh.h"
 #include "BKE_crazyspace.h"
+#include "BKE_crazyspace.hh"
+#include "BKE_curves.hh"
 #include "BKE_editmesh.h"
+#include "BKE_geometry_set.hh"
 #include "BKE_lib_id.h"
 #include "BKE_mesh.h"
 #include "BKE_mesh_wrapper.h"
@@ -586,3 +589,64 @@ void BKE_crazyspace_api_eval_clear(Object *object)
 }
 
 /** \} */
+
+namespace blender::bke::crazyspace {
+
+GeometryDeformation get_evaluated_curves_deformation(const Depsgraph &depsgraph,
+                                                     const Object &ob_orig)
+{
+  BLI_assert(ob_orig.type == OB_CURVES);
+  const Curves &curves_id_orig = *static_cast<const Curves *>(ob_orig.data);
+  const CurvesGeometry &curves_orig = CurvesGeometry::wrap(curves_id_orig.geometry);
+  const int points_num = curves_orig.points_num();
+
+  GeometryDeformation deformation;
+  /* Use the undeformed positions by default. */
+  deformation.positions = curves_orig.positions();
+
+  const Object *ob_eval = DEG_get_evaluated_object(&depsgraph, const_cast<Object *>(&ob_orig));
+  if (ob_eval == nullptr) {
+    return deformation;
+  }
+  const GeometrySet *geometry_eval = ob_eval->runtime.geometry_set_eval;
+  if (geometry_eval == nullptr) {
+    return deformation;
+  }
+
+  /* If available, use deformation information generated during evaluation. */
+  const GeometryComponentEditData *edit_component_eval =
+      geometry_eval->get_component_for_read<GeometryComponentEditData>();
+  bool uses_extra_positions = false;
+  if (edit_component_eval != nullptr) {
+    const CurvesEditHints *edit_hints = edit_component_eval->curves_edit_hints_.get();
+    if (edit_hints != nullptr && &edit_hints->curves_id_orig == &curves_id_orig) {
+      if (edit_hints->positions.has_value()) {
+        BLI_assert(edit_hints->positions->size() == points_num);
+        deformation.positions = *edit_hints->positions;
+        uses_extra_positions = true;
+      }
+      if (edit_hints->deform_mats.has_value()) {
+        BLI_assert(edit_hints->deform_mats->size() == points_num);
+        deformation.deform_mats = *edit_hints->deform_mats;
+      }
+    }
+  }
+
+  /* Use the positions of the evaluated curves directly, if the number of points matches. */
+  if (!uses_extra_positions) {
+    const CurveComponent *curves_component_eval =
+        geometry_eval->get_component_for_read<CurveComponent>();
+    if (curves_component_eval != nullptr) {
+      const Curves *curves_id_eval = curves_component_eval->get_for_read();
+      if (curves_id_eval != nullptr) {
+        const CurvesGeometry &curves_eval = CurvesGeometry::wrap(curves_id_eval->geometry);
+        if (curves_eval.points_num() == points_num) {
+          deformation.positions = curves_eval.positions();
+        }
+      }
+    }
+  }
+  return deformation;
+}
+
+}  // namespace blender::bke::crazyspace