1 files changed, 122 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/mesh_sample.cc b/source/blender/blenkernel/intern/mesh_sample.cc
index 91c9951ae89..f52098e9b40 100644
--- a/source/blender/blenkernel/intern/mesh_sample.cc
+++ b/source/blender/blenkernel/intern/mesh_sample.cc
@@ -14,6 +14,7 @@
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
+#include "BKE_attribute_access.hh"
 #include "BKE_attribute_math.hh"
 #include "BKE_mesh_runtime.h"
 #include "BKE_mesh_sample.hh"
@@ -23,7 +24,7 @@
 
 namespace blender::bke::mesh_surface_sample {
 
-static Span<MLoopTri> get_mesh_looptris(const Mesh &mesh)
+Span<MLoopTri> get_mesh_looptris(const Mesh &mesh)
 {
   /* This only updates a cache and can be considered to be logically const. */
   const MLoopTri *looptris = BKE_mesh_runtime_looptri_ensure(const_cast<Mesh *>(&mesh));
@@ -155,4 +156,124 @@ void sample_face_attribute(const Mesh &mesh,
   });
 }
 
+MeshAttributeInterpolator::MeshAttributeInterpolator(const Mesh *mesh,
+                                             const Span<float3> positions,
+                                             const Span<int> looptri_indices)
+    : mesh_(mesh), positions_(positions), looptri_indices_(looptri_indices)
+{
+  BLI_assert(positions.size() == looptri_indices.size());
+}
+
+Span<float3> MeshAttributeInterpolator::ensure_barycentric_coords()
+{
+  if (!bary_coords_.is_empty()) {
+    BLI_assert(bary_coords_.size() == positions_.size());
+    return bary_coords_;
+  }
+  bary_coords_.reinitialize(positions_.size());
+
+  Span<MLoopTri> looptris = get_mesh_looptris(*mesh_);
+
+  for (const int i : bary_coords_.index_range()) {
+    const int looptri_index = looptri_indices_[i];
+    const MLoopTri &looptri = looptris[looptri_index];
+
+    const int v0_index = mesh_->mloop[looptri.tri[0]].v;
+    const int v1_index = mesh_->mloop[looptri.tri[1]].v;
+    const int v2_index = mesh_->mloop[looptri.tri[2]].v;
+
+    interp_weights_tri_v3(bary_coords_[i],
+                          mesh_->mvert[v0_index].co,
+                          mesh_->mvert[v1_index].co,
+                          mesh_->mvert[v2_index].co,
+                          positions_[i]);
+  }
+  return bary_coords_;
+}
+
+Span<float3> MeshAttributeInterpolator::ensure_nearest_weights()
+{
+  if (!nearest_weights_.is_empty()) {
+    BLI_assert(nearest_weights_.size() == positions_.size());
+    return nearest_weights_;
+  }
+  nearest_weights_.reinitialize(positions_.size());
+
+  Span<MLoopTri> looptris = get_mesh_looptris(*mesh_);
+
+  for (const int i : nearest_weights_.index_range()) {
+    const int looptri_index = looptri_indices_[i];
+    const MLoopTri &looptri = looptris[looptri_index];
+
+    const int v0_index = mesh_->mloop[looptri.tri[0]].v;
+    const int v1_index = mesh_->mloop[looptri.tri[1]].v;
+    const int v2_index = mesh_->mloop[looptri.tri[2]].v;
+
+    const float d0 = len_squared_v3v3(positions_[i], mesh_->mvert[v0_index].co);
+    const float d1 = len_squared_v3v3(positions_[i], mesh_->mvert[v1_index].co);
+    const float d2 = len_squared_v3v3(positions_[i], mesh_->mvert[v2_index].co);
+
+    nearest_weights_[i] = MIN3_PAIR(d0, d1, d2, float3(1, 0, 0), float3(0, 1, 0), float3(0, 0, 1));
+  }
+  return nearest_weights_;
+}
+
+void MeshAttributeInterpolator::sample_attribute(const ReadAttributeLookup &src_attribute,
+                                             OutputAttribute &dst_attribute,
+                                             eAttributeMapMode mode)
+{
+  if (looptri_indices_.is_empty()) {
+    return;
+  }
+
+  if (!src_attribute || !dst_attribute) {
+    return;
+  }
+  const GVArray &src_varray = *src_attribute.varray;
+  GMutableSpan dst_span = dst_attribute.as_span();
+  if (src_varray.is_empty() || dst_span.is_empty()) {
+    return;
+  }
+
+  /* Compute barycentric coordinates only when they are needed. */
+  Span<float3> weights;
+  if (ELEM(src_attribute.domain, ATTR_DOMAIN_POINT, ATTR_DOMAIN_CORNER)) {
+    switch (mode) {
+      case eAttributeMapMode::INTERPOLATED:
+        weights = ensure_barycentric_coords();
+        break;
+      case eAttributeMapMode::NEAREST:
+        weights = ensure_nearest_weights();
+        break;
+    }
+  }
+
+  /* Interpolate the source attributes on the surface. */
+  switch (src_attribute.domain) {
+    case ATTR_DOMAIN_POINT: {
+      sample_point_attribute(
+          *mesh_, looptri_indices_, weights, src_varray, dst_span);
+      break;
+    }
+    case ATTR_DOMAIN_FACE: {
+      sample_face_attribute(
+          *mesh_, looptri_indices_, src_varray, dst_span);
+      break;
+    }
+    case ATTR_DOMAIN_CORNER: {
+      sample_corner_attribute(
+          *mesh_, looptri_indices_, weights, src_varray, dst_span);
+      break;
+    }
+    case ATTR_DOMAIN_EDGE: {
+      /* Not yet supported. */
+      break;
+    }
+    default: {
+      BLI_assert_unreachable();
+      break;
+    }
+  }
+}
+
 }  // namespace blender::bke::mesh_surface_sample