SamplePointsUniformly, F-Score and Chamfer Distance

cpp/open3d/t/geometry/Geometry.h

@@ -90,6 +90,22 @@ class Geometry : public core::IsDevice {
     int dimension_;
     std::string name_;
 };
+/// Metrics for comparing point clouds and triangle meshes.
+enum class Metric {
+    ChamferDistance,  ///< Chamfer Distance
+    FScore            ///< F-Score
+};
+
+/// Holder for various parameters required by metrics
+struct MetricParameters {
+    /// Radius for computing the F Score. A match between a point and its
+    /// nearest neighbor is sucessful if it is within this radius.
+    std::vector<float> fscore_radius = {0.01};
+    /// Points are sampled uniformly from the surface of triangle meshes before
+    /// distance computation. This specifies the number of points sampled. No
+    /// sampling is done for point clouds.
+    size_t n_sampled_points = 1000;
+};
 
 }  // namespace geometry
 }  // namespace t

cpp/open3d/t/geometry/PointCloud.cpp

@@ -34,6 +34,7 @@
 #include "open3d/t/geometry/TriangleMesh.h"
 #include "open3d/t/geometry/VtkUtils.h"
 #include "open3d/t/geometry/kernel/GeometryMacros.h"
+#include "open3d/t/geometry/kernel/Metrics.h"
 #include "open3d/t/geometry/kernel/PCAPartition.h"
 #include "open3d/t/geometry/kernel/PointCloud.h"
 #include "open3d/t/geometry/kernel/Transform.h"
@@ -1331,6 +1332,35 @@ int PointCloud::PCAPartition(int max_points) {
     return num_partitions;
 }
 
+std::vector<float> PointCloud::ComputeDistance(
+        const PointCloud &pcd2,
+        std::initializer_list<Metric> metrics,
+        MetricParameters params) const {
+    if (!IsCPU() || !pcd2.IsCPU()) {
+        utility::LogWarning(
+                "ComputeDistance is implemented only on CPU. Computing on "
+                "CPU.");
+    }
+    core::Tensor points1 = GetPointPositions().To(core::Device("CPU:0")),
+                 points2 = pcd2.GetPointPositions().To(core::Device("CPU:0"));
+    core::Tensor indices12, distance12, indices21, distance21;
+
+    core::nns::NearestNeighborSearch tree1(points1);
+    core::nns::NearestNeighborSearch tree2(points2);
+
+    if (!tree2.KnnIndex()) {
+        utility::LogError("[ComputeDistance] Building KNN-Index failed!");
+    }
+    if (!tree1.KnnIndex()) {
+        utility::LogError("[ComputeDistance] Building KNN-Index failed!");
+    }
+
+    std::tie(indices12, distance12) = tree2.KnnSearch(points1, 1);
+    std::tie(indices21, distance21) = tree2.KnnSearch(points2, 1);
+
+    return ComputeDistanceCommon(distance12, distance21, metrics, params);
+}
+
 }  // namespace geometry
 }  // namespace t
 }  // namespace open3d

cpp/open3d/t/geometry/PointCloud.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <initializer_list>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
@@ -697,6 +698,18 @@ class PointCloud : public Geometry, public DrawableGeometry {
     /// \return The number of partitions.
     int PCAPartition(int max_points);
 
+    /// Compute various distances / metrics between two point clouds. Currently,
+    /// Chamfer distance and F-Score are supported.
+    /// \param pcd2 Other point cloud to compare with.
+    /// \param metrics List of Metric s to compute.  Multiple metrics can be
+    /// computed at once for efficiency.
+    /// \param params MetricParameters struct holds parameters required by
+    /// different metrics.
+    std::vector<float> ComputeDistance(
+            const PointCloud &pcd2,
+            std::initializer_list<Metric> metrics = {Metric::ChamferDistance},
+            MetricParameters params = MetricParameters()) const;
+
 protected:
     core::Device device_ = core::Device("CPU:0");
     TensorMap point_attr_;

cpp/open3d/t/geometry/TriangleMesh.cpp

@@ -20,6 +20,8 @@
 #include <unordered_map>
 
 #include "open3d/core/CUDAUtils.h"
+#include "open3d/core/Device.h"
+#include "open3d/core/Dtype.h"
 #include "open3d/core/EigenConverter.h"
 #include "open3d/core/ShapeUtil.h"
 #include "open3d/core/Tensor.h"
@@ -28,6 +30,7 @@
 #include "open3d/t/geometry/PointCloud.h"
 #include "open3d/t/geometry/RaycastingScene.h"
 #include "open3d/t/geometry/VtkUtils.h"
+#include "open3d/t/geometry/kernel/Metrics.h"
 #include "open3d/t/geometry/kernel/PCAPartition.h"
 #include "open3d/t/geometry/kernel/PointCloud.h"
 #include "open3d/t/geometry/kernel/Transform.h"
@@ -315,6 +318,12 @@ TriangleMesh &TriangleMesh::ComputeTriangleAreas() {
         utility::LogWarning("TriangleMesh has no triangle indices.");
         return *this;
     }
+    if (HasTriangleAttr("areas")) {
+        utility::LogWarning(
+                "TriangleMesh already has triangle areas: remove "
+                "'areas' triangle attribute if you'd like to update.");
+        return *this;
+    }
 
     core::Tensor triangle_areas = ComputeTriangleAreasHelper(*this);
     SetTriangleAttr("areas", triangle_areas);
@@ -1404,7 +1413,9 @@ TriangleMesh TriangleMesh::RemoveNonManifoldEdges() {
     core::Tensor tris_cpu =
             GetTriangleIndices().To(core::Device()).Contiguous();
 
-    ComputeTriangleAreas();
+    if (!HasTriangleAttr("areas")) {
+        ComputeTriangleAreas();
+    }
     core::Tensor tri_areas_cpu =
             GetTriangleAttr("areas").To(core::Device()).Contiguous();
 
@@ -1507,6 +1518,107 @@ core::Tensor TriangleMesh::GetNonManifoldEdges(
     return result;
 }
 
+PointCloud TriangleMesh::SamplePointsUniformly(
+        size_t number_of_points, bool use_triangle_normal /*=false*/) {
+    if (number_of_points <= 0) {
+        utility::LogError("number_of_points <= 0");
+    }
+    if (IsEmpty()) {
+        utility::LogError("Input mesh is empty. Cannot sample points.");
+    }
+    if (!HasTriangleIndices()) {
+        utility::LogError("Input mesh has no triangles. Cannot sample points.");
+    }
+    if (use_triangle_normal && !HasTriangleNormals()) {
+        ComputeTriangleNormals(true);
+    }
+    if (!HasTriangleAttr("areas")) {
+        ComputeTriangleAreas();  // Compute area of each triangle
+    }
+    if (!IsCPU()) {
+        utility::LogWarning(
+                "SamplePointsUniformly is implemented only on CPU. Computing "
+                "on CPU.");
+    }
+    bool use_vert_normals = HasVertexNormals() && !use_triangle_normal;
+    bool use_albedo =
+            HasTriangleAttr("texture_uvs") && GetMaterial().HasAlbedoMap();
+    bool use_vert_colors = HasVertexColors() && !use_albedo;
+
+    auto cpu = core::Device();
+    core::Tensor null_tensor({0}, core::Float32);  // zero size tensor
+    auto triangles = GetTriangleIndices().To(cpu).Contiguous(),
+         vertices = GetVertexPositions().To(cpu).Contiguous();
+    auto float_dt = vertices.GetDtype();
+    auto areas = GetTriangleAttr("areas").To(cpu, float_dt).Contiguous(),
+         vertex_normals =
+                 use_vert_normals
+                         ? GetVertexNormals().To(cpu, float_dt).Contiguous()
+                         : null_tensor,
+         triangle_normals =
+                 use_triangle_normal
+                         ? GetTriangleNormals().To(cpu, float_dt).Contiguous()
+                         : null_tensor,
+         vertex_colors =
+                 use_vert_colors
+                         ? GetVertexColors().To(cpu, core::Float32).Contiguous()
+                         : null_tensor,
+         texture_uvs = use_albedo ? GetTriangleAttr("texture_uvs")
+                                            .To(cpu, float_dt)
+                                            .Contiguous()
+                                  : null_tensor,
+         // With correct range conversion [0,255] -> [0,1]
+            albedo = use_albedo ? GetMaterial()
+                                          .GetAlbedoMap()
+                                          .To(core::Float32)
+                                          .To(cpu)
+                                          .AsTensor()
+                                : null_tensor;
+    if (use_vert_colors) {
+        if (GetVertexColors().GetDtype() == core::UInt8) vertex_colors /= 255;
+        if (GetVertexColors().GetDtype() == core::UInt16)
+            vertex_colors /= 65535;
+    }
+
+    std::array<core::Tensor, 3> result =
+            kernel::trianglemesh::SamplePointsUniformlyCPU(
+                    triangles, vertices, areas, vertex_normals, vertex_colors,
+                    triangle_normals, texture_uvs, albedo, number_of_points);
+
+    PointCloud pcd(result[0]);
+    if (use_vert_normals || use_triangle_normal) pcd.SetPointNormals(result[1]);
+    if (use_albedo || use_vert_colors) pcd.SetPointColors(result[2]);
+    return pcd.To(GetDevice());
+}
+
+std::vector<float> TriangleMesh::ComputeDistance(
+        const TriangleMesh &mesh2,
+        std::initializer_list<Metric> metrics,
+        MetricParameters params) const {
+    if (!IsCPU() || !mesh2.IsCPU()) {
+        utility::LogWarning(
+                "ComputeDistance is implemented only on CPU. Computing on "
+                "CPU.");
+    }
+    auto cpu_mesh1 = To(core::Device("CPU:0")),
+         cpu_mesh2 = mesh2.To(core::Device("CPU:0"));
+    core::Tensor points1 =
+            cpu_mesh1.SamplePointsUniformly(params.n_sampled_points)
+                    .GetPointPositions();
+    core::Tensor points2 =
+            cpu_mesh2.SamplePointsUniformly(params.n_sampled_points)
+                    .GetPointPositions();
+
+    RaycastingScene scene1, scene2;
+    scene1.AddTriangles(cpu_mesh1);
+    scene2.AddTriangles(cpu_mesh2);
+
+    core::Tensor distance21 = scene1.ComputeDistance(points2);
+    core::Tensor distance12 = scene2.ComputeDistance(points1);
+
+    return ComputeDistanceCommon(distance12, distance21, metrics, params);
+}
+
 }  // namespace geometry
 }  // namespace t
 }  // namespace open3d

cpp/open3d/t/geometry/TriangleMesh.h

@@ -24,6 +24,7 @@ namespace t {
 namespace geometry {
 
 class LineSet;
+class PointCloud;
 
 /// \class TriangleMesh
 /// \brief A triangle mesh contains vertices and triangles.
@@ -1007,6 +1008,31 @@ class TriangleMesh : public Geometry, public DrawableGeometry {
     /// If mesh is empty or has no triangles, returns an empty tensor.
     core::Tensor GetNonManifoldEdges(bool allow_boundary_edges = true) const;
 
+    /// Sample points uniformly from the triangle mesh surface and return as a
+    /// PointCloud. Normals and colors are interpolated from the triangle mesh.
+    /// If texture_uvs and albedo are present, these are used to estimate the
+    /// sampled point color, otherwise vertex colors are used, if present.
+    /// During sampling, triangle areas are computed and saved in the "areas"
+    /// attribute.
+    /// \param number_of_points The number of points to sample.
+    /// \param use_triangle_normal If true, use the triangle normal as the
+    /// normal of the sampled point. Otherwise, interpolate the vertex normals.
+    PointCloud SamplePointsUniformly(size_t number_of_points,
+                                     bool use_triangle_normal = false);
+
+    /// Compute various distances / metrics between two triangle meshes. This
+    /// uses ray casting for distance computations between a triangle mesh and a
+    /// sampled point cloud.
+    /// \param mesh2 Other point cloud to compare with.
+    /// \param metrics List of Metric s to compute. Multiple metrics can be
+    /// computed at once for efficiency.
+    /// \param params MetricParameters struct holds parameters required by
+    /// different metrics.
+    std::vector<float> ComputeDistance(
+            const TriangleMesh &mesh2,
+            std::initializer_list<Metric> metrics = {Metric::ChamferDistance},
+            MetricParameters params = MetricParameters()) const;
+
 protected:
     core::Device device_ = core::Device("CPU:0");
     TensorMap vertex_attr_;

cpp/open3d/t/geometry/kernel/CMakeLists.txt

@@ -6,6 +6,7 @@ target_sources(tgeometry_kernel PRIVATE
     PCAPartition.cpp
     PointCloud.cpp
     PointCloudCPU.cpp
+    Metrics.cpp
     TriangleMesh.cpp
     TriangleMeshCPU.cpp
     Transform.cpp

cpp/open3d/t/geometry/kernel/Metrics.cpp

@@ -0,0 +1,58 @@
+// ----------------------------------------------------------------------------
+// -                        Open3D: www.open3d.org                            -
+// ----------------------------------------------------------------------------
+// Copyright (c) 2018-2024 www.open3d.org
+// SPDX-License-Identifier: MIT
+// ----------------------------------------------------------------------------
+
+#include <vector>
+
+#include "open3d/core/Tensor.h"
+#include "open3d/t/geometry/Geometry.h"
+namespace open3d {
+namespace t {
+namespace geometry {
+
+std::vector<float> OPEN3D_LOCAL
+ComputeDistanceCommon(core::Tensor distance12,
+                      core::Tensor distance21,
+                      std::initializer_list<Metric> metrics,
+                      MetricParameters params) {
+    std::vector<float> metric_values;
+    float metric_val;
+
+    for (Metric metric : metrics) {
+        switch (metric) {
+            case Metric::ChamferDistance:
+                metric_val = 0.5 * (distance21.Mean({-1}).Item<float>() +
+                                    distance12.Mean({-1}).Item<float>());
+                metric_values.push_back(metric_val);
+                break;
+            case Metric::FScore:
+                float *p_distance12 = distance12.GetDataPtr<float>(),
+                      *p_distance21 = distance21.GetDataPtr<float>();
+                for (float radius : params.fscore_radius) {
+                    // Workaround since we don't have Tensor::CountNonZeros
+                    float precision = 0., recall = 0.;
+                    for (size_t i = 0;
+                         i < static_cast<size_t>(distance12.GetLength()); ++i)
+                        precision += p_distance12[i] < radius;
+                    precision *= 100. / distance12.GetLength();
+                    for (size_t i = 0;
+                         i < static_cast<size_t>(distance21.GetLength()); ++i)
+                        recall += p_distance21[i] < radius;
+                    recall *= 100. / distance21.GetLength();
+                    float fscore = 0.0;
+                    if (precision + recall > 0) {
+                        fscore = 2 * precision * recall / (precision + recall);
+                    }
+                    metric_values.push_back(fscore);
+                }
+                break;
+        }
+    }
+    return metric_values;
+}
+}  // namespace geometry
+}  // namespace t
+}  // namespace open3d

cpp/open3d/t/geometry/kernel/Metrics.h

@@ -0,0 +1,22 @@
+// ----------------------------------------------------------------------------
+// -                        Open3D: www.open3d.org                            -
+// ----------------------------------------------------------------------------
+// Copyright (c) 2018-2024 www.open3d.org
+// SPDX-License-Identifier: MIT
+// ----------------------------------------------------------------------------
+
+#include <vector>
+
+#include "open3d/core/Tensor.h"
+#include "open3d/t/geometry/Geometry.h"
+namespace open3d {
+namespace t {
+namespace geometry {
+
+std::vector<float> ComputeDistanceCommon(core::Tensor distance12,
+                                         core::Tensor distance21,
+                                         std::initializer_list<Metric> metrics,
+                                         MetricParameters params);
+}
+}  // namespace t
+}  // namespace open3d

cpp/open3d/t/geometry/kernel/TriangleMesh.h

@@ -29,6 +29,17 @@ void ComputeTriangleAreasCPU(const core::Tensor& vertices,
                              const core::Tensor& triangles,
                              core::Tensor& triangle_areas);
 
+std::array<core::Tensor, 3> SamplePointsUniformlyCPU(
+        const core::Tensor& triangles,
+        const core::Tensor& vertices,
+        const core::Tensor& triangle_areas,
+        const core::Tensor& vertex_normals,
+        const core::Tensor& vertex_colors,
+        const core::Tensor& triangle_normals,
+        const core::Tensor& texture_uvs,
+        const core::Tensor& albedo,
+        size_t number_of_points);
+
 #ifdef BUILD_CUDA_MODULE
 void NormalizeNormalsCUDA(core::Tensor& normals);