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, 184 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/curve_eval.cc b/source/blender/blenkernel/intern/curve_eval.cc
new file mode 100644
index 00000000000..4c63c7f05ee
--- /dev/null
+++ b/source/blender/blenkernel/intern/curve_eval.cc
@@ -0,0 +1,184 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "BLI_array.hh"
+#include "BLI_listbase.h"
+#include "BLI_span.hh"
+
+#include "DNA_curve_types.h"
+
+#include "BKE_curve.h"
+#include "BKE_spline.hh"
+
+using blender::float3;
+using blender::float4x4;
+using blender::Span;
+
+CurveEval *CurveEval::copy()
+{
+  CurveEval *new_curve = new CurveEval();
+
+  for (SplinePtr &spline : this->splines) {
+    new_curve->splines.append(spline->copy());
+  }
+
+  return new_curve;
+}
+
+void CurveEval::translate(const float3 &translation)
+{
+  for (SplinePtr &spline : this->splines) {
+    spline->translate(translation);
+    spline->mark_cache_invalid();
+  }
+}
+
+void CurveEval::transform(const float4x4 &matrix)
+{
+  for (SplinePtr &spline : this->splines) {
+    spline->transform(matrix);
+  }
+}
+
+void CurveEval::bounds_min_max(float3 &min, float3 &max, const bool use_evaluated) const
+{
+  for (const SplinePtr &spline : this->splines) {
+    spline->bounds_min_max(min, max, use_evaluated);
+  }
+}
+
+static BezierSpline::HandleType handle_type_from_dna_bezt(const eBezTriple_Handle dna_handle_type)
+{
+  switch (dna_handle_type) {
+    case HD_FREE:
+      return BezierSpline::HandleType::Free;
+    case HD_AUTO:
+      return BezierSpline::HandleType::Auto;
+    case HD_VECT:
+      return BezierSpline::HandleType::Vector;
+    case HD_ALIGN:
+      return BezierSpline::HandleType::Align;
+    case HD_AUTO_ANIM:
+      return BezierSpline::HandleType::Auto;
+    case HD_ALIGN_DOUBLESIDE:
+      return BezierSpline::HandleType::Align;
+  }
+  BLI_assert_unreachable();
+  return BezierSpline::HandleType::Auto;
+}
+
+static Spline::NormalCalculationMode normal_mode_from_dna_curve(const int twist_mode)
+{
+  switch (twist_mode) {
+    case CU_TWIST_Z_UP:
+      return Spline::NormalCalculationMode::ZUp;
+    case CU_TWIST_MINIMUM:
+      return Spline::NormalCalculationMode::Minimum;
+    case CU_TWIST_TANGENT:
+      return Spline::NormalCalculationMode::Tangent;
+  }
+  BLI_assert_unreachable();
+  return Spline::NormalCalculationMode::Minimum;
+}
+
+static NURBSpline::KnotsMode knots_mode_from_dna_nurb(const short flag)
+{
+  switch (flag & (CU_NURB_ENDPOINT | CU_NURB_BEZIER)) {
+    case CU_NURB_ENDPOINT:
+      return NURBSpline::KnotsMode::EndPoint;
+    case CU_NURB_BEZIER:
+      return NURBSpline::KnotsMode::Bezier;
+    default:
+      return NURBSpline::KnotsMode::Normal;
+  }
+
+  BLI_assert_unreachable();
+  return NURBSpline::KnotsMode::Normal;
+}
+
+std::unique_ptr<CurveEval> curve_eval_from_dna_curve(const Curve &dna_curve)
+{
+  std::unique_ptr<CurveEval> curve = std::make_unique<CurveEval>();
+
+  const ListBase *nurbs = BKE_curve_nurbs_get(&const_cast<Curve &>(dna_curve));
+
+  curve->splines.reserve(BLI_listbase_count(nurbs));
+
+  /* TODO: Optimize by reserving the correct points size. */
+  LISTBASE_FOREACH (const Nurb *, nurb, nurbs) {
+    switch (nurb->type) {
+      case CU_BEZIER: {
+        std::unique_ptr<BezierSpline> spline = std::make_unique<BezierSpline>();
+        spline->set_resolution(nurb->resolu);
+        spline->set_cyclic(nurb->flagu & CU_NURB_CYCLIC);
+
+        for (const BezTriple &bezt : Span(nurb->bezt, nurb->pntsu)) {
+          spline->add_point(bezt.vec[1],
+                            handle_type_from_dna_bezt((eBezTriple_Handle)bezt.h1),
+                            bezt.vec[0],
+                            handle_type_from_dna_bezt((eBezTriple_Handle)bezt.h2),
+                            bezt.vec[2],
+                            bezt.radius,
+                            bezt.tilt);
+        }
+
+        curve->splines.append(std::move(spline));
+        break;
+      }
+      case CU_NURBS: {
+        std::unique_ptr<NURBSpline> spline = std::make_unique<NURBSpline>();
+        spline->set_resolution(nurb->resolu);
+        spline->set_cyclic(nurb->flagu & CU_NURB_CYCLIC);
+        spline->set_order(nurb->orderu);
+        spline->knots_mode = knots_mode_from_dna_nurb(nurb->flagu);
+
+        for (const BPoint &bp : Span(nurb->bp, nurb->pntsu)) {
+          spline->add_point(bp.vec, bp.radius, bp.tilt, bp.vec[3]);
+        }
+
+        curve->splines.append(std::move(spline));
+        break;
+      }
+      case CU_POLY: {
+        std::unique_ptr<PolySpline> spline = std::make_unique<PolySpline>();
+        spline->set_cyclic(nurb->flagu & CU_NURB_CYCLIC);
+
+        for (const BPoint &bp : Span(nurb->bp, nurb->pntsu)) {
+          spline->add_point(bp.vec, bp.radius, bp.tilt);
+        }
+
+        curve->splines.append(std::move(spline));
+        break;
+      }
+      default: {
+        BLI_assert_unreachable();
+        break;
+      }
+    }
+  }
+
+  /* Note: Normal mode is stored separately in each spline to facilitate combining splines
+   * from multiple curve objects, where the value may be different. */
+  const Spline::NormalCalculationMode normal_mode = normal_mode_from_dna_curve(
+      dna_curve.twist_mode);
+  for (SplinePtr &spline : curve->splines) {
+    spline->normal_mode = normal_mode;
+  }
+
+  return curve;
+}
+
+/** \} */