Curves: Interpolate point count in add brush

This commit adds an option to interpolate the number of control points
in new curves based on the count in neighboring existing curves. The
idea is to provide a more automatic default than manually controlling
the number of points in a curve, so users don't have to think about
the resolution quite as much.

Internally, some utilities for creating new curves are extracted to a
new header file. These can be used for the various nodes and operators
that create new curves.

The top-bar UI will be adjusted in a separate patch, probably moving
all of the settings that affect the size and shape of the new curves
into a popover.

Differential Revision: https://developer.blender.org/D14877

1 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_curves_utils.hh b/source/blender/blenkernel/BKE_curves_utils.hh
new file mode 100644
index 00000000000..62b060093e9
--- /dev/null
+++ b/source/blender/blenkernel/BKE_curves_utils.hh
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include "BKE_curves.hh"
+
+/** \file
+ * \ingroup bke
+ * \brief Low-level operations for curves.
+ */
+
+namespace blender::bke::curves {
+
+/**
+ * Copy the size of every curve in #curve_ranges to the corresponding index in #counts.
+ */
+void fill_curve_counts(const bke::CurvesGeometry &curves,
+                       Span<IndexRange> curve_ranges,
+                       MutableSpan<int> counts);
+
+/**
+ * Turn an array of sizes into the offset at each index including all previous sizes.
+ */
+void accumulate_counts_to_offsets(MutableSpan<int> counts_to_offsets, int start_offset = 0);
+
+}  // namespace blender::bke::curves