1 files changed, 64 insertions, 0 deletions
diff --git a/source/blender/blenlib/intern/length_parameterize.cc b/source/blender/blenlib/intern/length_parameterize.cc
index d6862b96944..7c0fc860b53 100644
--- a/source/blender/blenlib/intern/length_parameterize.cc
+++ b/source/blender/blenlib/intern/length_parameterize.cc
@@ -77,4 +77,68 @@ void create_uniform_samples(const Span<float> lengths,
   }
 }
 
+void create_samples_from_sorted_lengths(const Span<float> lengths,
+                                        const Span<float> sample_lengths,
+                                        const bool cyclic,
+                                        MutableSpan<int> indices,
+                                        MutableSpan<float> factors)
+{
+  BLI_assert(std::is_sorted(lengths.begin(), lengths.end()));
+  BLI_assert(std::is_sorted(sample_lengths.begin(), sample_lengths.end()));
+  BLI_assert(indices.size() == sample_lengths.size());
+  BLI_assert(indices.size() == factors.size());
+  const int segments_num = lengths.size();
+  const int points_num = cyclic ? segments_num : segments_num + 1;
+
+  const float total_length = lengths.last();
+  if (total_length == 0.0f) {
+    indices.fill(0);
+    factors.fill(0.0f);
+    return;
+  }
+
+  int i_dst = 0;
+  /* Store the length at the previous point in a variable so it can start out at zero
+   * (the lengths array doesn't contain 0 for the first point). */
+  float prev_length = 0.0f;
+  for (const int i_src : IndexRange(points_num - 1)) {
+    const float next_length = lengths[i_src];
+    const float segment_length = next_length - prev_length;
+    if (segment_length == 0.0f) {
+      continue;
+    }
+    /* Add every sample that fits in this segment. It's also necessary to check if the last sample
+     * has been reached, since there is no upper bound on the number of samples in each segment. */
+    const float segment_length_inv = 1.0f / segment_length;
+    while (i_dst < sample_lengths.size() && sample_lengths[i_dst] < next_length) {
+      const float length_in_segment = sample_lengths[i_dst] - prev_length;
+      const float factor = length_in_segment * segment_length_inv;
+      indices[i_dst] = i_src;
+      factors[i_dst] = factor;
+      i_dst++;
+    }
+
+    prev_length = next_length;
+  }
+
+  /* Add the samples on the last cyclic segment if necessary, and also the samples
+   * that weren't created in the previous loop due to floating point inaccuracy. */
+  if (cyclic && lengths.size() > 1) {
+    const float segment_length = lengths.last() - lengths.last(1);
+    while (sample_lengths[i_dst] < total_length) {
+      const float length_in_segment = sample_lengths[i_dst] - prev_length;
+      const float factor = length_in_segment / segment_length;
+      indices[i_dst] = points_num - 1;
+      factors[i_dst] = factor;
+      i_dst++;
+    }
+    indices.drop_front(i_dst).fill(points_num - 1);
+    factors.drop_front(i_dst).fill(1.0f);
+  }
+  else {
+    indices.drop_front(i_dst).fill(points_num - 2);
+    factors.drop_front(i_dst).fill(1.0f);
+  }
+}
+
 }  // namespace blender::length_parameterize