feat: move spline to helper in Visualization

Core/include/Acts/Visualization/Interpolation3D.hpp

@@ -0,0 +1,53 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#include "Acts/Definitions/Algebra.hpp"
+
+#include <unsupported/Eigen/Splines>
+
+namespace Acts::Interpolation3D {
+
+/// @brief Helper function to interpolate points using a spline
+/// from Eigen
+///
+/// @tparam input_vector_type
+/// @param inputs input vector points
+/// @param nPoints number of interpolation points
+///
+/// @return std::vector<Acts::Vector3> interpolated points
+template <typename input_vector_type>
+std::vector<Acts::Vector3> spline(const std::vector<input_vector_type>& inputs,
+                                  std::size_t nPoints) {
+  std::vector<Acts::Vector3> output;
+
+  if (nPoints < 2) {
+    // No interpolation done return simply the output vector
+    for (const auto& input : inputs) {
+      output.push_back(input.template head<3>());
+    }
+
+  } else {
+    Eigen::MatrixXd points(3, inputs.size());
+    for (std::size_t i = 0; i < inputs.size(); ++i) {
+      points.col(i) = inputs[i].template head<3>().transpose();
+    }
+    Eigen::Spline<double, 3> spline3D =
+        Eigen::SplineFitting<Eigen::Spline<double, 3>>::Interpolate(points, 2);
+
+    double step = 1. / (nPoints - 1);
+    for (std::size_t i = 0; i < nPoints; ++i) {
+      double t = i * step;
+      output.push_back(spline3D(t));
+    }
+  }
+  return output;
+}
+
+}  // namespace Acts::Interpolation3D

Examples/Io/Obj/src/ObjSimHitWriter.cpp

@@ -11,6 +11,7 @@
 #include "Acts/Definitions/Algebra.hpp"
 #include "Acts/Definitions/Common.hpp"
 #include "Acts/Geometry/GeometryIdentifier.hpp"
+#include "Acts/Visualization/Interpolation3D.hpp"
 #include "ActsExamples/EventData/SimHit.hpp"
 #include "ActsExamples/Framework/AlgorithmContext.hpp"
 #include "ActsExamples/Utilities/Paths.hpp"
@@ -22,47 +23,6 @@
 #include <unordered_map>
 #include <vector>
 
-#include <unsupported/Eigen/Splines>
-
-namespace {
-
-/// @brief Helper function to interpolate points
-///
-/// @tparam input_vector_type
-/// @param inputs input vector points
-/// @param nPoints number of interpolation points
-///
-/// @return std::vector<Acts::Vector3> interpolated points
-template <typename input_vector_type>
-std::vector<Acts::Vector3> interpolatedPoints(
-    const std::vector<input_vector_type>& inputs, std::size_t nPoints) {
-  std::vector<Acts::Vector3> output;
-
-  if (nPoints < 2) {
-    // No interpolation done return simply the output vector
-    for (const auto& input : inputs) {
-      output.push_back(input.template head<3>());
-    }
-
-  } else {
-    Eigen::MatrixXd points(3, inputs.size());
-    for (std::size_t i = 0; i < inputs.size(); ++i) {
-      points.col(i) = inputs[i].template head<3>().transpose();
-    }
-    Eigen::Spline<double, 3> spline3D =
-        Eigen::SplineFitting<Eigen::Spline<double, 3>>::Interpolate(points, 2);
-
-    double step = 1. / (nPoints - 1);
-    for (std::size_t i = 0; i < nPoints; ++i) {
-      double t = i * step;
-      output.push_back(spline3D(t));
-    }
-  }
-  return output;
-}
-
-}  // namespace
-
 ActsExamples::ObjSimHitWriter::ObjSimHitWriter(
     const ActsExamples::ObjSimHitWriter::Config& config,
     Acts::Logging::Level level)
@@ -159,8 +119,8 @@ ActsExamples::ProcessCode ActsExamples::ObjSimHitWriter::writeT(
           trajectory.push_back(hit.template head<3>());
         }
       } else {
-        trajectory =
-            interpolatedPoints(pHits, pHits.size() * m_cfg.nInterpolatedPoints);
+        trajectory = Acts::Interpolation3D::spline(
+            pHits, pHits.size() * m_cfg.nInterpolatedPoints);
       }
 
       osTrajectory << "o particle_trajectory_" << pId << std::endl;

Tests/UnitTests/Core/Visualization/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_unittest(Visualization3D Visualization3DTests.cpp)
 add_unittest(EventDataView3D EventDataView3DTests.cpp)
+add_unittest(Interpolation3D Interpolation3DTests.cpp)
 add_unittest(PrimitivesView3D PrimitivesView3DTests.cpp)
 add_unittest(SurfaceView3D SurfaceView3DTests.cpp)
 add_unittest(TrackingGeometryView3D TrackingGeometryView3DTests.cpp)

Tests/UnitTests/Core/Visualization/Interpolation3DTests.cpp

@@ -0,0 +1,51 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#include <boost/test/unit_test.hpp>
+#include <numbers>
+
+#include "Acts/Visualization/Interpolation3D.hpp"
+#include "Acts/Tests/CommonHelpers/FloatComparisons.hpp"
+
+namespace Acts::Test {
+
+BOOST_AUTO_TEST_SUITE(Visualization)
+
+BOOST_AUTO_TEST_CASE(SplineInterpolation) {
+
+    /// Define the input vector
+    double R = 10.;
+    std::vector<Acts::Vector3> inputs;
+    for (double phi = 0; phi < 2 * std::numbers::pi; phi += std::numbers::pi / 4) {
+        inputs.push_back(Acts::Vector3(R * cos(phi), R * sin(phi), 0.));
+    }
+
+    // Interpolate the points options
+    std::vector<Acts::Vector3> trajectory;
+
+    // (0) - nothing happens
+    trajectory = Acts::Interpolation3D::spline(inputs, 1);
+    // Check input and output size are the same
+    BOOST_CHECK_EQUAL(trajectory.size(), inputs.size());
+
+    // (1) - interpolate between the points with 12 points in total
+    trajectory = Acts::Interpolation3D::spline(inputs, 12);
+    // Check the output size is correct
+    BOOST_CHECK_EQUAL(trajectory.size(), 12);
+
+    for (const auto& point : trajectory) {
+        // Check the interpolated points are on the circle
+        // with a tolerance of course
+        CHECK_CLOSE_ABS(point.norm(), R, 0.1);
+    }
+
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+}  // namespace Acts::Test