feat: Add JSON detector element (#3851)

Add a json detector element, which is explicitly constructed from a `nlohmann::json` object in order to ensure consistency. Move json surface reading utilities from examples to Plugins.

Examples/Io/Json/CMakeLists.txt

@@ -4,7 +4,6 @@ add_library(
     src/JsonGeometryList.cpp
     src/JsonMaterialWriter.cpp
     src/JsonSurfacesWriter.cpp
-    src/JsonSurfacesReader.cpp
     src/JsonDigitizationConfig.cpp
 )
 target_include_directories(

Examples/Python/src/Detector.cpp

@@ -221,6 +221,12 @@ void addDetector(Context& ctx) {
 
     patchKwargsConstructor(c);
   }
+
+  {
+    py::class_<Acts::DetectorElementBase,
+               std::shared_ptr<Acts::DetectorElementBase>>(
+        mex, "DetectorElementBase");
+  }
 }
 
 }  // namespace Acts::Python

Examples/Python/src/Json.cpp

@@ -11,13 +11,13 @@
 #include "Acts/Detector/ProtoDetector.hpp"
 #include "Acts/Plugins/Json/DetectorJsonConverter.hpp"
 #include "Acts/Plugins/Json/JsonMaterialDecorator.hpp"
+#include "Acts/Plugins/Json/JsonSurfacesReader.hpp"
 #include "Acts/Plugins/Json/MaterialMapJsonConverter.hpp"
 #include "Acts/Plugins/Json/ProtoDetectorJsonConverter.hpp"
 #include "Acts/Plugins/Python/Utilities.hpp"
 #include "Acts/Utilities/Logger.hpp"
 #include "ActsExamples/Framework/ProcessCode.hpp"
 #include "ActsExamples/Io/Json/JsonMaterialWriter.hpp"
-#include "ActsExamples/Io/Json/JsonSurfacesReader.hpp"
 #include "ActsExamples/Io/Json/JsonSurfacesWriter.hpp"
 #include "ActsExamples/Io/Json/JsonTrackParamsLookupReader.hpp"
 #include "ActsExamples/Io/Json/JsonTrackParamsLookupWriter.hpp"
@@ -204,21 +204,29 @@ void addJson(Context& ctx) {
   }
 
   {
-    auto sjOptions = py::class_<ActsExamples::JsonSurfacesReader::Options>(
-                         mex, "SurfaceJsonOptions")
-                         .def(py::init<>());
+    auto sjOptions =
+        py::class_<Acts::JsonSurfacesReader::Options>(m, "SurfaceJsonOptions")
+            .def(py::init<>());
 
-    ACTS_PYTHON_STRUCT_BEGIN(sjOptions,
-                             ActsExamples::JsonSurfacesReader::Options);
+    ACTS_PYTHON_STRUCT_BEGIN(sjOptions, Acts::JsonSurfacesReader::Options);
     ACTS_PYTHON_MEMBER(inputFile);
     ACTS_PYTHON_MEMBER(jsonEntryPath);
     ACTS_PYTHON_STRUCT_END();
 
-    mex.def("readSurfaceHierarchyMapFromJson",
-            ActsExamples::JsonSurfacesReader::readHierarchyMap);
+    m.def("readSurfaceHierarchyMapFromJson",
+          Acts::JsonSurfacesReader::readHierarchyMap);
 
-    mex.def("readSurfaceVectorFromJson",
-            ActsExamples::JsonSurfacesReader::readVector);
+    m.def("readSurfaceVectorFromJson", Acts::JsonSurfacesReader::readVector);
+
+    py::class_<Acts::JsonDetectorElement, Acts::DetectorElementBase,
+               std::shared_ptr<Acts::JsonDetectorElement>>(
+        m, "JsonDetectorElement")
+        .def("surface", [](Acts::JsonDetectorElement& self) {
+          return self.surface().getSharedPtr();
+        });
+
+    m.def("readDetectorElementsFromJson",
+          Acts::JsonSurfacesReader::readDetectorElements);
   }
 
   {

Plugins/Json/CMakeLists.txt

@@ -22,6 +22,8 @@ add_library(
     src/VolumeJsonConverter.cpp
     src/AmbiguityConfigJsonConverter.cpp
     src/DetrayJsonHelper.cpp
+    src/JsonDetectorElement.cpp
+    src/JsonSurfacesReader.cpp
 )
 target_include_directories(
     ActsPluginJson

Plugins/Json/include/Acts/Plugins/Json/JsonDetectorElement.hpp

@@ -0,0 +1,38 @@
+// 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/Geometry/DetectorElementBase.hpp"
+
+#include <nlohmann/json.hpp>
+
+namespace Acts {
+
+/// A implementation of a detector element, that is constructed from a
+/// JSON description of a surface. The idea behind this is that it helps
+/// importing whole tracking geometries from JSON files. In some parts of
+/// the codebase, the existence of a detector element associated to a surface
+/// has a specific meaning (e.g., flags surfaces as sensitive).
+class JsonDetectorElement : public DetectorElementBase {
+ public:
+  JsonDetectorElement(const nlohmann::json &jSurface, double thickness);
+
+  Surface &surface() override;
+  const Surface &surface() const override;
+
+  double thickness() const override;
+
+  const Transform3 &transform(const GeometryContext &gctx) const override;
+
+ private:
+  std::shared_ptr<Surface> m_surface;
+  Transform3 m_transform{};
+  double m_thickness{};
+};
+
+}  // namespace Acts

Examples/Io/Json/include/ActsExamples/Io/Json/JsonSurfacesReader.hpp → Plugins/Json/include/Acts/Plugins/Json/JsonSurfacesReader.hpp

@@ -9,6 +9,7 @@
 #pragma once
 
 #include "Acts/Geometry/GeometryHierarchyMap.hpp"
+#include "Acts/Plugins/Json/JsonDetectorElement.hpp"
 
 #include <memory>
 #include <string>
@@ -18,9 +19,11 @@ namespace Acts {
 class Surface;
 }
 
-namespace ActsExamples::JsonSurfacesReader {
+namespace Acts::JsonSurfacesReader {
 
 /// @brief Options specification for surface reading
+/// The file should contain an array of json surfaces
+/// as produced by the SurfaceJsonConverter tools
 struct Options {
   /// @brief  Which input file to read from
   std::string inputFile = "";
@@ -29,6 +32,7 @@ struct Options {
 };
 
 /// @brief Read the surfaces from the input file
+/// For details on the file format see the options struct
 ///
 /// @param options specifies which file and what to read
 ///
@@ -37,10 +41,22 @@ Acts::GeometryHierarchyMap<std::shared_ptr<Acts::Surface>> readHierarchyMap(
     const Options& options);
 
 /// @brief Read the flat surfaces from the input file
+/// For details on the file format see the options struct
 ///
-/// @param inputFile is the input file to read from
+/// @param options options for surface reading
 ///
 /// @return  a vector of surfaces
 std::vector<std::shared_ptr<Acts::Surface>> readVector(const Options& options);
 
-}  // namespace ActsExamples::JsonSurfacesReader
+/// @brief Read the surfaces from the input file and create
+/// detector elements
+/// For details on the file format see the options struct
+///
+/// @param options options for surface reading
+/// @param thickness the thickness used to construct the detector element
+///
+/// @return  a vector of surfaces
+std::vector<std::shared_ptr<Acts::JsonDetectorElement>> readDetectorElements(
+    const Options& options, double thickness);
+
+}  // namespace Acts::JsonSurfacesReader

Plugins/Json/src/JsonDetectorElement.cpp

@@ -0,0 +1,41 @@
+// 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 "Acts/Plugins/Json/JsonDetectorElement.hpp"
+
+#include "Acts/Plugins/Json/AlgebraJsonConverter.hpp"
+#include "Acts/Plugins/Json/SurfaceJsonConverter.hpp"
+
+namespace Acts {
+
+JsonDetectorElement::JsonDetectorElement(const nlohmann::json &jSurface,
+                                         double thickness)
+    : m_thickness(thickness) {
+  m_surface = Acts::SurfaceJsonConverter::fromJson(jSurface);
+  m_transform = Transform3JsonConverter::fromJson(jSurface["transform"]);
+  m_surface->assignDetectorElement(*this);
+}
+
+const Surface &JsonDetectorElement::surface() const {
+  return *m_surface;
+}
+
+Surface &JsonDetectorElement::surface() {
+  return *m_surface;
+}
+
+const Transform3 &JsonDetectorElement::transform(
+    const GeometryContext & /*gctx*/) const {
+  return m_transform;
+}
+
+double JsonDetectorElement::thickness() const {
+  return m_thickness;
+}
+
+}  // namespace Acts

Examples/Io/Json/src/JsonSurfacesReader.cpp → Plugins/Json/src/JsonSurfacesReader.cpp

@@ -6,7 +6,7 @@
 // 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 "ActsExamples/Io/Json/JsonSurfacesReader.hpp"
+#include "Acts/Plugins/Json/JsonSurfacesReader.hpp"
 
 #include "Acts/Geometry/GeometryIdentifier.hpp"
 #include "Acts/Plugins/Json/ActsJson.hpp"
@@ -17,7 +17,7 @@
 #include <fstream>
 #include <iostream>
 
-namespace ActsExamples {
+namespace Acts {
 
 Acts::GeometryHierarchyMap<std::shared_ptr<Acts::Surface>>
 JsonSurfacesReader::readHierarchyMap(
@@ -73,4 +73,27 @@ std::vector<std::shared_ptr<Acts::Surface>> JsonSurfacesReader::readVector(
   return surfaces;
 }
 
-}  // namespace ActsExamples
+std::vector<std::shared_ptr<Acts::JsonDetectorElement>>
+JsonSurfacesReader::readDetectorElements(const Options& options,
+                                         double thickness = 0.0) {
+  nlohmann::json j;
+  {
+    std::ifstream in(options.inputFile);
+    in >> j;
+  }
+
+  // Walk down the path to the surface entries
+  nlohmann::json jSurfaces = j;
+  for (const auto& jep : options.jsonEntryPath) {
+    jSurfaces = jSurfaces[jep];
+  }
+
+  std::vector<std::shared_ptr<Acts::JsonDetectorElement>> elements;
+  for (const auto& jSurface : jSurfaces) {
+    elements.emplace_back(
+        std::make_shared<Acts::JsonDetectorElement>(jSurface, thickness));
+  }
+  return elements;
+}
+
+}  // namespace Acts

Tests/UnitTests/Plugins/Json/CMakeLists.txt

@@ -16,3 +16,4 @@ add_unittest(SurfaceBoundsJsonConverter SurfaceBoundsJsonConverterTests.cpp)
 add_unittest(SurfaceJsonConverter SurfaceJsonConverterTests.cpp)
 add_unittest(VolumeBoundsJsonConverter VolumeBoundsJsonConverterTests.cpp)
 add_unittest(TrackParametersJsonConverter TrackParametersJsonConverterTests.cpp)
+add_unittest(JsonSurfacesReader JsonSurfacesReaderTests.cpp)

Tests/UnitTests/Plugins/Json/JsonSurfacesReaderTests.cpp

@@ -0,0 +1,98 @@
+// 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 <boost/test/unit_test_suite.hpp>
+
+#include "Acts/Definitions/Algebra.hpp"
+#include "Acts/Geometry/GeometryContext.hpp"
+#include "Acts/Geometry/GeometryIdentifier.hpp"
+#include "Acts/Plugins/Json/JsonSurfacesReader.hpp"
+#include "Acts/Plugins/Json/SurfaceJsonConverter.hpp"
+#include "Acts/Surfaces/PlaneSurface.hpp"
+#include "Acts/Surfaces/RectangleBounds.hpp"
+#include "Acts/Utilities/Zip.hpp"
+
+#include <filesystem>
+#include <fstream>
+#include <memory>
+
+#include <Eigen/Geometry>
+#include <nlohmann/json.hpp>
+
+const std::vector<std::shared_ptr<Acts::Surface>> surfaces = []() {
+  std::vector<std::shared_ptr<Acts::Surface>> v;
+
+  for (int i = 0; i < 3; ++i) {
+    auto bounds = std::make_shared<Acts::RectangleBounds>(1.0, 1.0);
+    Acts::Transform3 transform = Acts::Transform3::Identity();
+    transform.translate(Acts::Vector3::Random());
+    Acts::Vector3 randomAngles = Acts::Vector3::Random();
+    Acts::SquareMatrix3 rotMatrix;
+    rotMatrix = Eigen::AngleAxis(randomAngles[0], Acts::Vector3::UnitX()) *
+                Eigen::AngleAxis(randomAngles[1], Acts::Vector3::UnitY()) *
+                Eigen::AngleAxis(randomAngles[2], Acts::Vector3::UnitZ());
+    transform.rotate(rotMatrix);
+    v.push_back(
+        Acts::Surface::makeShared<Acts::PlaneSurface>(transform, bounds));
+  }
+
+  return v;
+}();
+
+const std::string filename = "json_surfaces_reader_tests.json";
+
+struct FileFixture {
+  FileFixture() {
+    nlohmann::json js = nlohmann::json::array();
+
+    for (const auto &s : surfaces) {
+      js.push_back(Acts::SurfaceJsonConverter::toJson({}, *s));
+    }
+
+    nlohmann::json j;
+    j["foo"] = js;
+
+    std::ofstream f(filename);
+    f << j.dump(2);
+  }
+
+  ~FileFixture() { std::filesystem::remove(filename); }
+};
+
+FileFixture fileFixture;
+
+BOOST_AUTO_TEST_CASE(surface_reading_test) {
+  auto readBackSurfaces =
+      Acts::JsonSurfacesReader::readVector({filename, {"foo"}});
+
+  BOOST_REQUIRE_EQUAL(surfaces.size(), readBackSurfaces.size());
+  for (auto [refSurface, surface] : Acts::zip(surfaces, readBackSurfaces)) {
+    BOOST_CHECK(
+        refSurface->transform({}).isApprox(surface->transform({}), 1.e-4));
+    BOOST_CHECK(refSurface->center({}).isApprox(surface->center({}), 1.e-4));
+    BOOST_CHECK_EQUAL(refSurface->type(), surface->type());
+    BOOST_CHECK_EQUAL(refSurface->bounds().type(), surface->bounds().type());
+  }
+}
+
+BOOST_AUTO_TEST_CASE(json_detelement_reading_test) {
+  auto readBackDetElements =
+      Acts::JsonSurfacesReader::readDetectorElements({filename, {"foo"}}, 1.0);
+
+  BOOST_REQUIRE_EQUAL(surfaces.size(), readBackDetElements.size());
+  for (auto [refSurface, detElement] :
+       Acts::zip(surfaces, readBackDetElements)) {
+    auto surface = &detElement->surface();
+    BOOST_CHECK(
+        refSurface->transform({}).isApprox(surface->transform({}), 1.e-4));
+    BOOST_CHECK(refSurface->center({}).isApprox(surface->center({}), 1.e-4));
+    BOOST_CHECK_EQUAL(refSurface->type(), surface->type());
+    BOOST_CHECK_EQUAL(refSurface->bounds().type(), surface->bounds().type());
+  }
+}

docs/_extensions/lazy_autodoc.py

@@ -117,6 +117,7 @@ def run() -> None:
         "Acts::Logging::DefaultFilterPolicy",
         "Acts::Logging::DefaultPrintPolicy",
         "Acts::SourceLink",
+        "Acts::JsonDetectorElement",
     }
 
     role_instances["func"] = {