feat: Add standalone digitization coordinates converter

Examples/Algorithms/Digitization/CMakeLists.txt

@@ -3,6 +3,7 @@ add_library(
     SHARED
     src/DigitizationAlgorithm.cpp
     src/DigitizationConfig.cpp
+    src/DigitizationCoordinatesConverter.cpp
     src/MeasurementCreation.cpp
     src/DigitizationConfigurator.cpp
     src/ModuleClusters.cpp

Examples/Algorithms/Digitization/include/ActsExamples/Digitization/DigitizationCoordinatesConverter.hpp

@@ -0,0 +1,39 @@
+// This file is part of the Acts project.
+//
+// Copyright (C) 2024 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 http://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#include "ActsExamples/Digitization/DigitizationConfig.hpp"
+
+namespace ActsExamples {
+
+/// Utility that converts hit coordinates.
+class DigitizationCoordinatesConverter final {
+ public:
+  /// Construct the converter
+  ///
+  /// @param config is the configuration
+  DigitizationCoordinatesConverter(DigitizationConfig config);
+
+  /// Get const access to the config
+  const DigitizationConfig& config() const { return m_cfg; }
+
+  /// Convert the hit coordinates to the local frame.
+  std::tuple<double, double> globalToLocal(std::uint64_t moduleId, double x,
+                                           double y, double z) const;
+
+  /// Convert the hit coordinates to the global frame.
+  std::tuple<double, double, double> localToGlobal(std::uint64_t moduleId,
+                                                   double x, double y) const;
+
+ private:
+  /// Configuration
+  DigitizationConfig m_cfg;
+};
+
+}  // namespace ActsExamples

Examples/Algorithms/Digitization/src/DigitizationCoordinatesConverter.cpp

@@ -0,0 +1,63 @@
+// This file is part of the Acts project.
+//
+// Copyright (C) 2024 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 http://mozilla.org/MPL/2.0/.
+
+#include "ActsExamples/Digitization/DigitizationCoordinatesConverter.hpp"
+
+#include "Acts/Definitions/Algebra.hpp"
+#include "Acts/Geometry/GeometryContext.hpp"
+
+#include <cmath>
+#include <stdexcept>
+#include <utility>
+
+ActsExamples::DigitizationCoordinatesConverter::
+    DigitizationCoordinatesConverter(DigitizationConfig config)
+    : m_cfg(std::move(config)) {
+  if (m_cfg.surfaceByIdentifier.empty()) {
+    throw std::invalid_argument("Missing Surface-GeometryID association map");
+  }
+}
+
+std::tuple<double, double>
+ActsExamples::DigitizationCoordinatesConverter::globalToLocal(
+    std::uint64_t moduleId, double x, double y, double z) const {
+  const Acts::GeometryIdentifier moduleGeoId = moduleId;
+  auto surfaceItr = m_cfg.surfaceByIdentifier.find(moduleGeoId);
+  if (surfaceItr == m_cfg.surfaceByIdentifier.end()) {
+    throw std::runtime_error("Surface not found for moduleGeoId");
+  }
+
+  // Transform the position into the local surface frame
+  const Acts::Surface* surfacePtr = surfaceItr->second;
+  const auto& invTransform =
+      surfacePtr->transform(Acts::GeometryContext()).inverse();
+
+  const Acts::Vector3 pos(x, y, z);
+  Acts::Vector2 pos2Local = (invTransform * pos).segment<2>(0);
+
+  return {pos2Local.x(), pos2Local.y()};
+}
+
+std::tuple<double, double, double>
+ActsExamples::DigitizationCoordinatesConverter::localToGlobal(
+    std::uint64_t moduleId, double x, double y) const {
+  const Acts::GeometryIdentifier moduleGeoId = moduleId;
+  auto surfaceItr = m_cfg.surfaceByIdentifier.find(moduleGeoId);
+  if (surfaceItr == m_cfg.surfaceByIdentifier.end()) {
+    throw std::runtime_error("Surface not found for moduleGeoId");
+  }
+
+  // Transform the position into the global frame
+  const Acts::Surface* surfacePtr = surfaceItr->second;
+  const auto& transform = surfacePtr->transform(Acts::GeometryContext());
+
+  const Acts::Vector3 pos(x, y, 0);
+  Acts::Vector3 pos2Global = (transform * pos);
+
+  return {pos2Global.x(), pos2Global.y(), pos2Global.z()};
+}

Examples/Python/src/Digitization.cpp

@@ -13,6 +13,7 @@
 #include "ActsExamples/Digitization/DigitizationAlgorithm.hpp"
 #include "ActsExamples/Digitization/DigitizationConfig.hpp"
 #include "ActsExamples/Digitization/DigitizationConfigurator.hpp"
+#include "ActsExamples/Digitization/DigitizationCoordinatesConverter.hpp"
 #include "ActsExamples/Framework/AlgorithmContext.hpp"
 #include "ActsExamples/Io/Json/JsonDigitizationConfig.hpp"
 
@@ -101,6 +102,19 @@ void addDigitization(Context& ctx) {
     ACTS_PYTHON_MEMBER(outputDigiComponents);
     ACTS_PYTHON_STRUCT_END();
   }
+
+  {
+    py::class_<ActsExamples::DigitizationCoordinatesConverter,
+               std::shared_ptr<ActsExamples::DigitizationCoordinatesConverter>>(
+        mex, "DigitizationCoordinatesConverter")
+        .def(py::init<ActsExamples::DigitizationConfig&>(), py::arg("config"))
+        .def_property_readonly(
+            "config", &ActsExamples::DigitizationCoordinatesConverter::config)
+        .def("globalToLocal",
+             &ActsExamples::DigitizationCoordinatesConverter::globalToLocal)
+        .def("localToGlobal",
+             &ActsExamples::DigitizationCoordinatesConverter::localToGlobal);
+  }
 }
 
 }  // namespace Acts::Python