ray_line_intersector.hpp

// 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
 
// Project include(s)
#include "detray/definitions/algebra.hpp"
#include "detray/definitions/detail/qualifiers.hpp"
#include "detray/definitions/math.hpp"
#include "detray/definitions/units.hpp"
#include "detray/geometry/coordinates/line2D.hpp"
#include "detray/navigation/intersection/intersection.hpp"
#include "detray/tracks/ray.hpp"
 
// System include(s)
#include <type_traits>
 
namespace detray {
 
template <typename frame_t, concepts::algebra algebra_t, bool resolve_pos>
struct ray_intersector_impl;

template <detray::concepts::aos algebra_t, bool resolve_pos>
struct ray_intersector_impl<line2D<algebra_t>, algebra_t, resolve_pos> {
  using algebra_type = algebra_t;
  using frame_type = line2D<algebra_t>;
  using point_type = dpoint3D<algebra_t>;

  template <typename surface_descr_t>
  using intersection_type =
      intersection2D<surface_descr_t, algebra_t, resolve_pos>;

  template <typename other_algebra_t>
  using trajectory_type = detail::ray<other_algebra_t>;

  static constexpr std::uint8_t n_solutions{1u};

  using result_type =
      intersection_point<algebra_t, point_type, intersection::contains_pos>;

  DETRAY_HOST_DEVICE constexpr result_type point_of_intersection(
      const trajectory_type<algebra_t> &ray, const dtransform3D<algebra_t> &trf,
      const dscalar<algebra_t> /*overstep_tol*/ = 0.f) const {
    using scalar_t = dscalar<algebra_t>;
    using point3_t = dpoint3D<algebra_t>;
    using vector3_t = dvector3D<algebra_t>;
 
    const vector3_t &rd = ray.dir();
    const point3_t &ro = ray.pos();
 
    // line direction
    const vector3_t &_z = trf.z();
    // line center
    const point3_t &_t = trf.translation();
 
    // Projection of line to track direction
    const scalar_t zd{vector::dot(_z, rd)};
 
    const scalar_t denom{1.f - (zd * zd)};
 
    // Case for wire is parallel to track
    if (denom < 1e-5f) [[unlikely]] {
      return {};
    }
 
    // vector from track position to line center
    const point3_t t2l = _t - ro;
 
    // t2l projection on line direction
    const scalar_t t2l_on_line{vector::dot(t2l, _z)};
 
    // t2l projection on track direction
    const scalar_t t2l_on_track{vector::dot(t2l, rd)};
 
    // path length to the point of closest approach on the track
    const scalar_t s{1.f / denom * (t2l_on_track - t2l_on_line * zd)};
    const point3_t glob_pos = ro + s * rd;
 
    return {s, glob_pos};
  }
};
 
}  // namespace detray