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-rw-r--r--source/blender/blenkernel/BKE_curves.hh18
-rw-r--r--source/blender/blenkernel/intern/curves_geometry.cc21
-rw-r--r--source/blender/blenlib/BLI_virtual_array.hh2
-rw-r--r--source/blender/editors/curves/CMakeLists.txt1
-rw-r--r--source/blender/editors/curves/intern/curves_ops.cc110
-rw-r--r--source/blender/editors/object/object_add.cc6
-rw-r--r--source/blender/editors/sculpt_paint/CMakeLists.txt1
-rw-r--r--source/blender/editors/sculpt_paint/curves_sculpt_add.cc51
-rw-r--r--source/blender/geometry/CMakeLists.txt2
-rw-r--r--source/blender/geometry/GEO_reverse_uv_sampler.hh42
-rw-r--r--source/blender/geometry/intern/reverse_uv_sampler.cc32
11 files changed, 203 insertions, 83 deletions
diff --git a/source/blender/blenkernel/BKE_curves.hh b/source/blender/blenkernel/BKE_curves.hh
index 168b17bad30..dc67f1e7403 100644
--- a/source/blender/blenkernel/BKE_curves.hh
+++ b/source/blender/blenkernel/BKE_curves.hh
@@ -264,22 +264,10 @@ class CurvesGeometry : public ::CurvesGeometry {
MutableSpan<float> nurbs_weights_for_write();
/**
- * The index of a triangle (#MLoopTri) that a curve is attached to.
- * The index is -1, if the curve is not attached.
+ * UV coordinate for each curve that encodes where the curve is attached to the surface mesh.
*/
- VArray<int> surface_triangle_indices() const;
- MutableSpan<int> surface_triangle_indices_for_write();
-
- /**
- * Barycentric coordinates of the attachment point within a triangle.
- * Only the first two coordinates are stored. The third coordinate can be derived because the sum
- * of the three coordinates is 1.
- *
- * When the triangle index is -1, this coordinate should be ignored.
- * The span can be empty, when all triangle indices are -1.
- */
- Span<float2> surface_triangle_coords() const;
- MutableSpan<float2> surface_triangle_coords_for_write();
+ Span<float2> surface_uv_coords() const;
+ MutableSpan<float2> surface_uv_coords_for_write();
VArray<float> selection_point_float() const;
MutableSpan<float> selection_point_float_for_write();
diff --git a/source/blender/blenkernel/intern/curves_geometry.cc b/source/blender/blenkernel/intern/curves_geometry.cc
index c2e67d853c9..2fa31bd4100 100644
--- a/source/blender/blenkernel/intern/curves_geometry.cc
+++ b/source/blender/blenkernel/intern/curves_geometry.cc
@@ -35,10 +35,9 @@ static const std::string ATTR_HANDLE_POSITION_RIGHT = "handle_right";
static const std::string ATTR_NURBS_ORDER = "nurbs_order";
static const std::string ATTR_NURBS_WEIGHT = "nurbs_weight";
static const std::string ATTR_NURBS_KNOTS_MODE = "knots_mode";
-static const std::string ATTR_SURFACE_TRIANGLE_INDEX = "surface_triangle_index";
-static const std::string ATTR_SURFACE_TRIANGLE_COORDINATE = "surface_triangle_coordinate";
static const std::string ATTR_SELECTION_POINT_FLOAT = ".selection_point_float";
static const std::string ATTR_SELECTION_CURVE_FLOAT = ".selection_curve_float";
+static const std::string ATTR_SURFACE_UV_COORDINATE = "surface_uv_coordinate";
/* -------------------------------------------------------------------- */
/** \name Constructors/Destructor
@@ -419,24 +418,14 @@ MutableSpan<int8_t> CurvesGeometry::nurbs_knots_modes_for_write()
return get_mutable_attribute<int8_t>(*this, ATTR_DOMAIN_CURVE, ATTR_NURBS_KNOTS_MODE, 0);
}
-VArray<int> CurvesGeometry::surface_triangle_indices() const
+Span<float2> CurvesGeometry::surface_uv_coords() const
{
- return get_varray_attribute<int>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_TRIANGLE_INDEX, -1);
+ return get_span_attribute<float2>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_UV_COORDINATE);
}
-MutableSpan<int> CurvesGeometry::surface_triangle_indices_for_write()
+MutableSpan<float2> CurvesGeometry::surface_uv_coords_for_write()
{
- return get_mutable_attribute<int>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_TRIANGLE_INDEX, -1);
-}
-
-Span<float2> CurvesGeometry::surface_triangle_coords() const
-{
- return get_span_attribute<float2>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_TRIANGLE_COORDINATE);
-}
-
-MutableSpan<float2> CurvesGeometry::surface_triangle_coords_for_write()
-{
- return get_mutable_attribute<float2>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_TRIANGLE_COORDINATE);
+ return get_mutable_attribute<float2>(*this, ATTR_DOMAIN_CURVE, ATTR_SURFACE_UV_COORDINATE);
}
VArray<float> CurvesGeometry::selection_point_float() const
diff --git a/source/blender/blenlib/BLI_virtual_array.hh b/source/blender/blenlib/BLI_virtual_array.hh
index ab4ca185ddb..0705d423f01 100644
--- a/source/blender/blenlib/BLI_virtual_array.hh
+++ b/source/blender/blenlib/BLI_virtual_array.hh
@@ -1138,6 +1138,8 @@ template<typename T> class VArray_Span final : public Span<T> {
Array<T> owned_data_;
public:
+ VArray_Span() = default;
+
VArray_Span(VArray<T> varray) : Span<T>(), varray_(std::move(varray))
{
this->size_ = varray_.size();
diff --git a/source/blender/editors/curves/CMakeLists.txt b/source/blender/editors/curves/CMakeLists.txt
index a5d8390e7f2..3c31e8014ff 100644
--- a/source/blender/editors/curves/CMakeLists.txt
+++ b/source/blender/editors/curves/CMakeLists.txt
@@ -7,6 +7,7 @@ set(INC
../../blentranslation
../../depsgraph
../../functions
+ ../../geometry
../../makesdna
../../makesrna
../../windowmanager
diff --git a/source/blender/editors/curves/intern/curves_ops.cc b/source/blender/editors/curves/intern/curves_ops.cc
index 85214e1608d..54f0a0208fb 100644
--- a/source/blender/editors/curves/intern/curves_ops.cc
+++ b/source/blender/editors/curves/intern/curves_ops.cc
@@ -17,6 +17,7 @@
#include "WM_api.h"
+#include "BKE_attribute_math.hh"
#include "BKE_bvhutils.h"
#include "BKE_context.h"
#include "BKE_curves.hh"
@@ -45,6 +46,8 @@
#include "RNA_enum_types.h"
#include "RNA_prototypes.h"
+#include "GEO_reverse_uv_sampler.hh"
+
/**
* The code below uses a suffix naming convention to indicate the coordinate space:
* `cu`: Local space of the curves object that is being edited.
@@ -184,25 +187,20 @@ static void try_convert_single_object(Object &curves_ob,
}
Mesh &surface_me = *static_cast<Mesh *>(surface_ob.data);
+ BVHTreeFromMesh surface_bvh;
+ BKE_bvhtree_from_mesh_get(&surface_bvh, &surface_me, BVHTREE_FROM_LOOPTRI, 2);
+ BLI_SCOPED_DEFER([&]() { free_bvhtree_from_mesh(&surface_bvh); });
+
const Span<float3> positions_cu = curves.positions();
- const VArray<int> looptri_indices = curves.surface_triangle_indices();
const Span<MLoopTri> looptris{BKE_mesh_runtime_looptri_ensure(&surface_me),
BKE_mesh_runtime_looptri_len(&surface_me)};
- /* Find indices of curves that can be transferred to the old hair system. */
- Vector<int> curves_indices_to_transfer;
- for (const int curve_i : curves.curves_range()) {
- const int looptri_i = looptri_indices[curve_i];
- if (looptri_i >= 0 && looptri_i < looptris.size()) {
- curves_indices_to_transfer.append(curve_i);
- }
- else {
- *r_could_not_convert_some_curves = true;
- }
+ if (looptris.is_empty()) {
+ *r_could_not_convert_some_curves = true;
}
- const int hairs_num = curves_indices_to_transfer.size();
- if (hairs_num == 0) {
+ const int hair_num = curves.curves_num();
+ if (hair_num == 0) {
return;
}
@@ -228,8 +226,8 @@ static void try_convert_single_object(Object &curves_ob,
psys_changed_type(&surface_ob, particle_system);
MutableSpan<ParticleData> particles{
- static_cast<ParticleData *>(MEM_calloc_arrayN(hairs_num, sizeof(ParticleData), __func__)),
- hairs_num};
+ static_cast<ParticleData *>(MEM_calloc_arrayN(hair_num, sizeof(ParticleData), __func__)),
+ hair_num};
/* The old hair system still uses #MFace, so make sure those are available on the mesh. */
BKE_mesh_tessface_calc(&surface_me);
@@ -250,17 +248,23 @@ static void try_convert_single_object(Object &curves_ob,
const float4x4 world_to_surface_mat = surface_to_world_mat.inverted();
const float4x4 curves_to_surface_mat = world_to_surface_mat * curves_to_world_mat;
- for (const int new_hair_i : curves_indices_to_transfer.index_range()) {
- const int curve_i = curves_indices_to_transfer[new_hair_i];
+ for (const int new_hair_i : IndexRange(hair_num)) {
+ const int curve_i = new_hair_i;
const IndexRange points = curves.points_for_curve(curve_i);
- const int looptri_i = looptri_indices[curve_i];
- const MLoopTri &looptri = looptris[looptri_i];
- const int poly_i = looptri.poly;
-
const float3 &root_pos_cu = positions_cu[points.first()];
const float3 root_pos_su = curves_to_surface_mat * root_pos_cu;
+ BVHTreeNearest nearest;
+ nearest.dist_sq = FLT_MAX;
+ BLI_bvhtree_find_nearest(
+ surface_bvh.tree, root_pos_su, &nearest, surface_bvh.nearest_callback, &surface_bvh);
+ BLI_assert(nearest.index >= 0);
+
+ const int looptri_i = nearest.index;
+ const MLoopTri &looptri = looptris[looptri_i];
+ const int poly_i = looptri.poly;
+
const int mface_i = find_mface_for_root_position(
surface_me, poly_to_mface_map[poly_i], root_pos_su);
const MFace &mface = surface_me.mface[mface_i];
@@ -520,7 +524,7 @@ static int snap_curves_to_surface_exec(bContext *C, wmOperator *op)
{
const AttachMode attach_mode = static_cast<AttachMode>(RNA_enum_get(op->ptr, "attach_mode"));
- std::atomic<bool> found_invalid_looptri_index = false;
+ std::atomic<bool> found_invalid_uv = false;
CTX_DATA_BEGIN (C, Object *, curves_ob, selected_objects) {
if (curves_ob->type != OB_CURVES) {
@@ -537,9 +541,19 @@ static int snap_curves_to_surface_exec(bContext *C, wmOperator *op)
}
Mesh &surface_mesh = *static_cast<Mesh *>(surface_ob.data);
+ MeshComponent surface_mesh_component;
+ surface_mesh_component.replace(&surface_mesh, GeometryOwnershipType::ReadOnly);
+
+ VArray_Span<float2> surface_uv_map;
+ if (curves_id.surface_uv_map != nullptr) {
+ surface_uv_map = surface_mesh_component
+ .attribute_try_get_for_read(
+ curves_id.surface_uv_map, ATTR_DOMAIN_CORNER, CD_PROP_FLOAT2)
+ .typed<float2>();
+ }
+
MutableSpan<float3> positions_cu = curves.positions_for_write();
- MutableSpan<int> surface_triangle_indices = curves.surface_triangle_indices_for_write();
- MutableSpan<float2> surface_triangle_coords = curves.surface_triangle_coords_for_write();
+ MutableSpan<float2> surface_uv_coords = curves.surface_uv_coords_for_write();
const Span<MLoopTri> surface_looptris = {BKE_mesh_runtime_looptri_ensure(&surface_mesh),
BKE_mesh_runtime_looptri_len(&surface_mesh)};
@@ -585,36 +599,50 @@ static int snap_curves_to_surface_exec(bContext *C, wmOperator *op)
pos_cu += pos_diff_cu;
}
- surface_triangle_indices[curve_i] = looptri_index;
-
- const MLoopTri &looptri = surface_looptris[looptri_index];
- const float3 &p0_su = surface_mesh.mvert[surface_mesh.mloop[looptri.tri[0]].v].co;
- const float3 &p1_su = surface_mesh.mvert[surface_mesh.mloop[looptri.tri[1]].v].co;
- const float3 &p2_su = surface_mesh.mvert[surface_mesh.mloop[looptri.tri[2]].v].co;
- float3 bary_coords;
- interp_weights_tri_v3(bary_coords, p0_su, p1_su, p2_su, new_first_point_pos_su);
- surface_triangle_coords[curve_i] = bke::curves::encode_surface_bary_coord(bary_coords);
+ if (!surface_uv_map.is_empty()) {
+ const MLoopTri &looptri = surface_looptris[looptri_index];
+ const int corner0 = looptri.tri[0];
+ const int corner1 = looptri.tri[1];
+ const int corner2 = looptri.tri[2];
+ const float2 &uv0 = surface_uv_map[corner0];
+ const float2 &uv1 = surface_uv_map[corner1];
+ const float2 &uv2 = surface_uv_map[corner2];
+ const float3 &p0_su = surface_mesh.mvert[surface_mesh.mloop[corner0].v].co;
+ const float3 &p1_su = surface_mesh.mvert[surface_mesh.mloop[corner1].v].co;
+ const float3 &p2_su = surface_mesh.mvert[surface_mesh.mloop[corner2].v].co;
+ float3 bary_coords;
+ interp_weights_tri_v3(bary_coords, p0_su, p1_su, p2_su, new_first_point_pos_su);
+ const float2 uv = attribute_math::mix3(bary_coords, uv0, uv1, uv2);
+ surface_uv_coords[curve_i] = uv;
+ }
}
});
break;
}
case AttachMode::Deform: {
+ if (!surface_uv_map.is_empty()) {
+ BKE_report(op->reports,
+ RPT_ERROR,
+ "Curves do not have attachment information that can be used for deformation");
+ }
+ using geometry::ReverseUVSampler;
+ ReverseUVSampler reverse_uv_sampler{surface_uv_map, surface_looptris};
+
threading::parallel_for(curves.curves_range(), 256, [&](const IndexRange curves_range) {
for (const int curve_i : curves_range) {
const IndexRange points = curves.points_for_curve(curve_i);
const int first_point_i = points.first();
const float3 old_first_point_pos_cu = positions_cu[first_point_i];
- const int looptri_index = surface_triangle_indices[curve_i];
- if (!surface_looptris.index_range().contains(looptri_index)) {
- found_invalid_looptri_index = true;
+ const float2 uv = surface_uv_coords[curve_i];
+ ReverseUVSampler::Result lookup_result = reverse_uv_sampler.sample(uv);
+ if (lookup_result.type != ReverseUVSampler::ResultType::Ok) {
+ found_invalid_uv = true;
continue;
}
- const MLoopTri &looptri = surface_looptris[looptri_index];
-
- const float3 bary_coords = bke::curves::decode_surface_bary_coord(
- surface_triangle_coords[curve_i]);
+ const MLoopTri &looptri = *lookup_result.looptri;
+ const float3 &bary_coords = lookup_result.bary_weights;
const float3 &p0_su = surface_mesh.mvert[surface_mesh.mloop[looptri.tri[0]].v].co;
const float3 &p1_su = surface_mesh.mvert[surface_mesh.mloop[looptri.tri[1]].v].co;
@@ -638,7 +666,7 @@ static int snap_curves_to_surface_exec(bContext *C, wmOperator *op)
}
CTX_DATA_END;
- if (found_invalid_looptri_index) {
+ if (found_invalid_uv) {
BKE_report(op->reports, RPT_INFO, "Could not snap some curves to the surface");
}
diff --git a/source/blender/editors/object/object_add.cc b/source/blender/editors/object/object_add.cc
index 5e09948e192..041a1383b28 100644
--- a/source/blender/editors/object/object_add.cc
+++ b/source/blender/editors/object/object_add.cc
@@ -2086,6 +2086,12 @@ static int object_curves_empty_hair_add_exec(bContext *C, wmOperator *op)
Curves *curves_id = static_cast<Curves *>(object->data);
curves_id->surface = surface_ob;
id_us_plus(&surface_ob->id);
+
+ Mesh *surface_mesh = static_cast<Mesh *>(surface_ob->data);
+ const char *uv_name = CustomData_get_active_layer_name(&surface_mesh->ldata, CD_MLOOPUV);
+ if (uv_name != nullptr) {
+ curves_id->surface_uv_map = BLI_strdup(uv_name);
+ }
}
return OPERATOR_FINISHED;
diff --git a/source/blender/editors/sculpt_paint/CMakeLists.txt b/source/blender/editors/sculpt_paint/CMakeLists.txt
index dfd8f8b1bb9..9a9efc9e6cf 100644
--- a/source/blender/editors/sculpt_paint/CMakeLists.txt
+++ b/source/blender/editors/sculpt_paint/CMakeLists.txt
@@ -10,6 +10,7 @@ set(INC
../../depsgraph
../../draw
../../functions
+ ../../geometry
../../gpu
../../imbuf
../../makesdna
diff --git a/source/blender/editors/sculpt_paint/curves_sculpt_add.cc b/source/blender/editors/sculpt_paint/curves_sculpt_add.cc
index 390f142ac0f..5f168bd4e05 100644
--- a/source/blender/editors/sculpt_paint/curves_sculpt_add.cc
+++ b/source/blender/editors/sculpt_paint/curves_sculpt_add.cc
@@ -19,6 +19,7 @@
#include "BKE_context.h"
#include "BKE_curves.hh"
#include "BKE_curves_utils.hh"
+#include "BKE_geometry_set.hh"
#include "BKE_mesh.h"
#include "BKE_mesh_runtime.h"
#include "BKE_paint.h"
@@ -95,6 +96,7 @@ struct AddOperationExecutor {
Mesh *surface_ = nullptr;
Span<MLoopTri> surface_looptris_;
Span<float3> corner_normals_su_;
+ VArray_Span<float2> surface_uv_map_;
const CurvesSculpt *curves_sculpt_ = nullptr;
const Brush *brush_ = nullptr;
@@ -114,6 +116,7 @@ struct AddOperationExecutor {
/** Various matrices to convert between coordinate spaces. */
float4x4 curves_to_world_mat_;
+ float4x4 curves_to_surface_mat_;
float4x4 world_to_curves_mat_;
float4x4 world_to_surface_mat_;
float4x4 surface_to_world_mat_;
@@ -165,6 +168,7 @@ struct AddOperationExecutor {
world_to_surface_mat_ = surface_to_world_mat_.inverted();
surface_to_curves_mat_ = world_to_curves_mat_ * surface_to_world_mat_;
surface_to_curves_normal_mat_ = surface_to_curves_mat_.inverted().transposed();
+ curves_to_surface_mat_ = curves_to_world_mat_ * world_to_surface_mat_;
if (!CustomData_has_layer(&surface_->ldata, CD_NORMAL)) {
BKE_mesh_calc_normals_split(surface_);
@@ -208,6 +212,15 @@ struct AddOperationExecutor {
surface_looptris_ = {BKE_mesh_runtime_looptri_ensure(surface_),
BKE_mesh_runtime_looptri_len(surface_)};
+ if (curves_id_->surface_uv_map != nullptr) {
+ MeshComponent surface_component;
+ surface_component.replace(surface_, GeometryOwnershipType::ReadOnly);
+ surface_uv_map_ = surface_component
+ .attribute_try_get_for_read(curves_id_->surface_uv_map,
+ ATTR_DOMAIN_CORNER)
+ .typed<float2>();
+ }
+
/* Sample points on the surface using one of multiple strategies. */
AddedPoints added_points;
if (add_amount_ == 1) {
@@ -652,7 +665,9 @@ struct AddOperationExecutor {
}
Array<float3> new_normals_su = this->compute_normals_for_added_curves_su(added_points);
- this->initialize_surface_attachment(added_points);
+ if (!surface_uv_map_.is_empty()) {
+ this->initialize_surface_attachment(added_points);
+ }
this->fill_new_selection();
@@ -775,14 +790,18 @@ struct AddOperationExecutor {
void initialize_surface_attachment(const AddedPoints &added_points)
{
- MutableSpan<int> surface_triangle_indices = curves_->surface_triangle_indices_for_write();
- MutableSpan<float2> surface_triangle_coords = curves_->surface_triangle_coords_for_write();
+ MutableSpan<float2> surface_uv_coords = curves_->surface_uv_coords_for_write();
threading::parallel_for(
added_points.bary_coords.index_range(), 1024, [&](const IndexRange range) {
for (const int i : range) {
const int curve_i = tot_old_curves_ + i;
- surface_triangle_indices[curve_i] = added_points.looptri_indices[i];
- surface_triangle_coords[curve_i] = float2(added_points.bary_coords[i]);
+ const MLoopTri &looptri = surface_looptris_[added_points.looptri_indices[i]];
+ const float2 &uv0 = surface_uv_map_[looptri.tri[0]];
+ const float2 &uv1 = surface_uv_map_[looptri.tri[1]];
+ const float2 &uv2 = surface_uv_map_[looptri.tri[2]];
+ const float3 &bary_coords = added_points.bary_coords[i];
+ const float2 uv = attribute_math::mix3(bary_coords, uv0, uv1, uv2);
+ surface_uv_coords[curve_i] = uv;
}
});
}
@@ -820,8 +839,6 @@ struct AddOperationExecutor {
const Span<float> new_lengths_cu)
{
MutableSpan<float3> positions_cu = curves_->positions_for_write();
- const VArray_Span<int> surface_triangle_indices{curves_->surface_triangle_indices()};
- const Span<float2> surface_triangle_coords = curves_->surface_triangle_coords();
threading::parallel_for(
added_points.bary_coords.index_range(), 256, [&](const IndexRange range) {
@@ -846,10 +863,22 @@ struct AddOperationExecutor {
for (const NeighborInfo &neighbor : neighbors) {
const int neighbor_curve_i = neighbor.index;
- const int neighbor_looptri_index = surface_triangle_indices[neighbor_curve_i];
-
- float3 neighbor_bary_coord{surface_triangle_coords[neighbor_curve_i]};
- neighbor_bary_coord.z = 1.0f - neighbor_bary_coord.x - neighbor_bary_coord.y;
+ const float3 &neighbor_first_pos_cu =
+ positions_cu[curves_->offsets()[neighbor_curve_i]];
+ const float3 neighbor_first_pos_su = curves_to_surface_mat_ * neighbor_first_pos_cu;
+
+ BVHTreeNearest nearest;
+ nearest.dist_sq = FLT_MAX;
+ BLI_bvhtree_find_nearest(surface_bvh_.tree,
+ neighbor_first_pos_su,
+ &nearest,
+ surface_bvh_.nearest_callback,
+ &surface_bvh_);
+ const int neighbor_looptri_index = nearest.index;
+ const MLoopTri &neighbor_looptri = surface_looptris_[neighbor_looptri_index];
+
+ const float3 neighbor_bary_coord = this->get_bary_coords(
+ *surface_, neighbor_looptri, nearest.co);
const float3 neighbor_normal_su = this->compute_point_normal_su(
neighbor_looptri_index, neighbor_bary_coord);
diff --git a/source/blender/geometry/CMakeLists.txt b/source/blender/geometry/CMakeLists.txt
index 010c327d482..1916c5f91f3 100644
--- a/source/blender/geometry/CMakeLists.txt
+++ b/source/blender/geometry/CMakeLists.txt
@@ -21,6 +21,7 @@ set(SRC
intern/point_merge_by_distance.cc
intern/realize_instances.cc
intern/resample_curves.cc
+ intern/reverse_uv_sampler.cc
intern/uv_parametrizer.c
GEO_mesh_merge_by_distance.hh
@@ -29,6 +30,7 @@ set(SRC
GEO_point_merge_by_distance.hh
GEO_realize_instances.hh
GEO_resample_curves.hh
+ GEO_reverse_uv_sampler.hh
GEO_uv_parametrizer.h
)
diff --git a/source/blender/geometry/GEO_reverse_uv_sampler.hh b/source/blender/geometry/GEO_reverse_uv_sampler.hh
new file mode 100644
index 00000000000..d392b65eaf4
--- /dev/null
+++ b/source/blender/geometry/GEO_reverse_uv_sampler.hh
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include <optional>
+
+#include "BLI_math_vector.hh"
+#include "BLI_span.hh"
+
+#include "DNA_meshdata_types.h"
+
+namespace blender::geometry {
+
+/**
+ * Can find the polygon/triangle that maps to a specific uv coordinate.
+ *
+ * \note this uses a trivial implementation currently that has to be replaced.
+ */
+class ReverseUVSampler {
+ private:
+ const Span<float2> uv_map_;
+ const Span<MLoopTri> looptris_;
+
+ public:
+ ReverseUVSampler(const Span<float2> uv_map, const Span<MLoopTri> looptris);
+
+ enum class ResultType {
+ None,
+ Ok,
+ Multiple,
+ };
+
+ struct Result {
+ ResultType type = ResultType::None;
+ const MLoopTri *looptri = nullptr;
+ float3 bary_weights;
+ };
+
+ Result sample(const float2 &query_uv) const;
+};
+
+} // namespace blender::geometry
diff --git a/source/blender/geometry/intern/reverse_uv_sampler.cc b/source/blender/geometry/intern/reverse_uv_sampler.cc
new file mode 100644
index 00000000000..9aa98895a86
--- /dev/null
+++ b/source/blender/geometry/intern/reverse_uv_sampler.cc
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "GEO_reverse_uv_sampler.hh"
+
+#include "BLI_math_geom.h"
+
+namespace blender::geometry {
+
+ReverseUVSampler::ReverseUVSampler(const Span<float2> uv_map, const Span<MLoopTri> looptris)
+ : uv_map_(uv_map), looptris_(looptris)
+{
+}
+
+ReverseUVSampler::Result ReverseUVSampler::sample(const float2 &query_uv) const
+{
+ for (const MLoopTri &looptri : looptris_) {
+ const float2 &uv0 = uv_map_[looptri.tri[0]];
+ const float2 &uv1 = uv_map_[looptri.tri[1]];
+ const float2 &uv2 = uv_map_[looptri.tri[2]];
+ float3 bary_weights;
+ if (!barycentric_coords_v2(uv0, uv1, uv2, query_uv, bary_weights)) {
+ continue;
+ }
+ if (IN_RANGE_INCL(bary_weights.x, 0.0f, 1.0f) && IN_RANGE_INCL(bary_weights.y, 0.0f, 1.0f) &&
+ IN_RANGE_INCL(bary_weights.z, 0.0f, 1.0f)) {
+ return Result{ResultType::Ok, &looptri, bary_weights};
+ }
+ }
+ return Result{};
+}
+
+} // namespace blender::geometry
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