Curves: Use copied original data for invalid NURBS curves

NURBS curves can be invalid when the order is less than the number
of points, or in a few other situations. Currently the evaluated data of
an invalid NURBS curve is empty. This is inconvenient because it
requires checking for empty curves when it otherwise wouldn't be
necessary. This patch replaces that fallback with copying the original
data to the evaluated points. This makes conceptual sense too, as if
the curve couldn't be evaluated-- which wouldn't necessarily delete it.

Usually the UI protects against this happening, but it's currently
possible to create an invalid curve with some operations like the
delete geometry node.

Differential Revision: https://developer.blender.org/D14837

1 files changed, 5 insertions, 9 deletions

diff --git a/source/blender/blenkernel/intern/curves_geometry.cc b/source/blender/blenkernel/intern/curves_geometry.cc
index 7a09b87490b..3ec5ee928f4 100644
--- a/source/blender/blenkernel/intern/curves_geometry.cc
+++ b/source/blender/blenkernel/intern/curves_geometry.cc
@@ -577,6 +577,11 @@ void CurvesGeometry::ensure_nurbs_basis_cache() const
         const bool is_cyclic = cyclic[curve_index];
         const KnotsMode mode = KnotsMode(knots_modes[curve_index]);
 
+        if (!curves::nurbs::check_valid_size_and_order(points.size(), order, is_cyclic, mode)) {
+          basis_caches[curve_index].invalid = true;
+          continue;
+        }
+
         const int knots_size = curves::nurbs::knots_size(points.size(), order, is_cyclic);
         Array<float> knots(knots_size);
         curves::nurbs::calculate_knots(points.size(), mode, order, is_cyclic, knots);
@@ -696,9 +701,6 @@ Span<float3> CurvesGeometry::evaluated_tangents() const
     threading::parallel_for(this->curves_range(), 128, [&](IndexRange curves_range) {
       for (const int curve_index : curves_range) {
         const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
-        if (UNLIKELY(evaluated_points.is_empty())) {
-          continue;
-        }
         curves::poly::calculate_tangents(evaluated_positions.slice(evaluated_points),
                                          cyclic[curve_index],
                                          tangents.slice(evaluated_points));
@@ -773,9 +775,6 @@ Span<float3> CurvesGeometry::evaluated_normals() const
 
       for (const int curve_index : curves_range) {
         const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
-        if (UNLIKELY(evaluated_points.is_empty())) {
-          continue;
-        }
         switch (normal_mode[curve_index]) {
           case NORMAL_MODE_Z_UP:
             curves::poly::calculate_normals_z_up(evaluated_tangents.slice(evaluated_points),
@@ -916,9 +915,6 @@ void CurvesGeometry::ensure_evaluated_lengths() const
       for (const int curve_index : curves_range) {
         const bool cyclic = curves_cyclic[curve_index];
         const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
-        if (UNLIKELY(evaluated_points.is_empty())) {
-          continue;
-        }
         const IndexRange lengths_range = this->lengths_range_for_curve(curve_index, cyclic);
         length_parameterize::accumulate_lengths(evaluated_positions.slice(evaluated_points),
                                                 cyclic,