Line data    Source code

       1             : // SPDX-License-Identifier: BSD-3-Clause
       2             : // Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
       3             : #include "scipp/variable/inv.h"
       4             : 
       5             : #include "scipp/common/overloaded.h"
       6             : #include "scipp/core/element/arg_list.h"
       7             : #include "scipp/core/spatial_transforms.h"
       8             : #include "scipp/core/transform_common.h"
       9             : 
      10             : #include "scipp/variable/transform.h"
      11             : 
      12             : namespace scipp::variable {
      13             : namespace element {
      14             : constexpr auto inv =
      15             :     overloaded{core::element::arg_list<Eigen::Matrix3d, Eigen::Affine3d,
      16             :                                        core::Translation, core::Quaternion>,
      17             :                core::transform_flags::expect_no_variance_arg<0>,
      18             :                core::transform_flags::expect_no_variance_arg<1>,
      19          24 :                [](const auto &transform) { return transform.inverse(); },
      20          18 :                [](const units::Unit &) {
      21             :                  // The resulting unit depends on the dtype;
      22             :                  // the calling code assigns it.
      23          18 :                  return units::none;
      24             :                }};
      25             : } // namespace element
      26             : 
      27             : namespace {
      28          18 : bool is_transform_with_translation(const Variable &var) {
      29          18 :   const auto dt = var.dtype();
      30          18 :   return dt == dtype<Eigen::Affine3d> || dt == dtype<scipp::core::Translation>;
      31             : }
      32             : 
      33             : // Translations: The unit stays the same because translations are additive.
      34             : // Affine transforms: The unit applies only to the translation part, see above.
      35             : // Linear transforms: Can scale the input, the unit is multiplicative.
      36             : // Rotations: A unit is ill-defined, but use 1/u to cancel out any unit
      37             : //            in case the user sets one manually.
      38          18 : auto result_unit(const Variable &var) {
      39          24 :   return is_transform_with_translation(var) ? var.unit()
      40          24 :                                             : units::one / var.unit();
      41             : }
      42             : 
      43             : } // namespace
      44             : 
      45          18 : Variable inv(const Variable &var) {
      46          18 :   auto res = variable::transform(var, element::inv, "inverse");
      47          18 :   res.setUnit(result_unit(var));
      48          18 :   return res;
      49           0 : }
      50             : } // namespace scipp::variable