Splines: Add API functions for interpolating data

First, expand on the interpolation to evaluated points with a templated
helper function, and a function that takes a GSPan. Next, add a set of
functions to `Spline` for interpolating at arbitrary intervals between
the evaluated points. The code for doing that isn't that complicated
anyway, but it's nice to avoid repeating, and it might make it easier
to unroll the special cases for the first and last points if we require
the index factors to be sorted.

1 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_spline.hh b/source/blender/blenkernel/BKE_spline.hh
index fc1292e3620..dfbe82f31fd 100644
--- a/source/blender/blenkernel/BKE_spline.hh
+++ b/source/blender/blenkernel/BKE_spline.hh
@@ -172,6 +172,25 @@ class Spline {
   blender::Array<float> sample_uniform_index_factors(const int samples_size) const;
   LookupResult lookup_data_from_index_factor(const float index_factor) const;
 
+  void sample_based_on_index_factors(const blender::fn::GVArray &src,
+                                     blender::Span<float> index_factors,
+                                     blender::fn::GMutableSpan dst) const;
+  template<typename T>
+  void sample_based_on_index_factors(const blender::VArray<T> &src,
+                                     blender::Span<float> index_factors,
+                                     blender::MutableSpan<T> dst) const
+  {
+    this->sample_based_on_index_factors(
+        blender::fn::GVArray_For_VArray(src), index_factors, blender::fn::GMutableSpan(dst));
+  }
+  template<typename T>
+  void sample_based_on_index_factors(blender::Span<T> src,
+                                     blender::Span<float> index_factors,
+                                     blender::MutableSpan<T> dst) const
+  {
+    this->sample_based_on_index_factors(blender::VArray_For_Span(src), index_factors, dst);
+  }
+
   /**
    * Interpolate a virtual array of data with the size of the number of control points to the
    * evaluated points. For poly splines, the lifetime of the returned virtual array must not
@@ -179,6 +198,13 @@ class Spline {
    */
   virtual blender::fn::GVArrayPtr interpolate_to_evaluated_points(
       const blender::fn::GVArray &source_data) const = 0;
+  blender::fn::GVArrayPtr interpolate_to_evaluated_points(blender::fn::GSpan data) const;
+  template<typename T>
+  blender::fn::GVArray_Typed<T> interpolate_to_evaluated_points(blender::Span<T> data) const
+  {
+    return blender::fn::GVArray_Typed<T>(
+        this->interpolate_to_evaluated_points(blender::fn::GSpan(data)));
+  }
 
  protected:
   virtual void correct_end_tangents() const = 0;