CGAL 6.2 - Shape Regularization

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CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap > Class Template Reference
Reference Manual » Segments

`#include <CGAL/Shape_regularization/Segments/Offset_regularization_2.h>`

## Definition

template<typename GeomTraits, typename InputRange, typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>
class CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >

An offset-based regularization type for 2D segments that reinforces collinearity relationships.

The input groups of segments should each contain (near) parallel segments. In order to achieve that, one may use the class `Segments::Angle_regularization_2` or the function `Segments::parallel_groups()`. Each group of parallel segments may be inserted using the method `add_group()`.

Template Parameters

  GeomTraits | a model of `Kernel`
  InputRange | a model of `Range` whose iterator type is `RandomAccessIterator`
  SegmentMap | a model of `ReadWritePropertyMap` whose key type is the value type of the `InputRange` and value type is `GeomTraits::Segment_2`. The default is `CGAL::Identity_property_map<typename GeomTraits::Segment_2>`.

Is model of
  `RegularizationType`

Examples
  Shape_regularization/regularize_100_segments_offsets.cpp, Shape_regularization/regularize_15_segments.cpp, and Shape_regularization/regularize_real_data_2.cpp.

## Types
typedef GeomTraits::FT | FT
| Number type.

## Initialization
template<typename NamedParameters = parameters::Default_named_parameters>
| Offset_regularization_2 (InputRange &input_range, const NamedParameters &np=parameters::default_values())
| initializes all internal data structures.
template<typename IndexRange >
void | add_group (const IndexRange &index_range)
| inserts a group of segments from `input_range`.

## Access
FT | target (const std::size_t i, const std::size_t j) const
| calculates the target value between 2 parallel segments, which are direct neighbors to each other.
FT | bound (const std::size_t) const
| returns `maximum_offset`.
void | update (const std::vector< FT > &solution)
| applies new positions computed by the `QuadraticProgramTraits` to the initial segments.

## Groups
template<typename OutIterator >
OutIterator | collinear_groups (OutIterator groups) const
| creates groups of indices, where each group represents collinear segments.

## Miscellaneous
std::size_t | number_of_modified_segments () const
| returns the number of modified segments.
template<typename OutIterator >
OutIterator | unique_segments (OutIterator segments) const
| returns segments, which best-fit collinear groups.

## Memory Management
void | clear ()
| clears all internal data structures.

## Constructor & Destructor Documentation

## ◆ Offset_regularization_2()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>
template<typename NamedParameters = parameters::Default_named_parameters>

CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::Offset_regularization_2 | ( | InputRange & | input_range,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

initializes all internal data structures.

Template Parameters

  NamedParameters | a sequence of Named Parameters

Parameters

  input_range | a range of 2D segments to be regularized
  np | an optional sequence of Named Parameters among the ones listed below; this parameter can be omitted, the default values are then used

Optional Named Parameters

  maximum allowed orthogonal distance between two parallel segments such that they are considered to be collinear Type: `GeomTraits::FT` Default: 0.5 unit length |
  an instance of `SegmentMap` that maps an item from `input_range` to `GeomTraits::Segment_2` Default: `SegmentMap()` |

Precondition
  input_range.size() >= 2
  maximum_offset >= 0

## Member Function Documentation

## ◆ add_group()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>
template<typename IndexRange >

void CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::add_group | ( | const IndexRange & | index_range | ) |

inserts a group of segments from `input_range`.

Each group of segments is provided as a collection of their indices and only segments within the group are being regularized that is no relationships between segments from different groups are taken into account.

The user must not use this method until he has meaningful groups of segments (see more in the user manual). By default, all segments are inserted as a group.

Template Parameters

  IndexRange | a model of `ConstRange` whose value type is `std::size_t`

Parameters

  index_range | a const range of segment indices

Precondition
  index_range.size() >= 2

## ◆ collinear_groups()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>
template<typename OutIterator >

OutIterator CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::collinear_groups | ( | OutIterator | groups | ) | const

creates groups of indices, where each group represents collinear segments.

This method calls `Segments::collinear_groups()`.

Template Parameters

  OutIterator | a model of `OutputIterator` that accepts elements of type `std::vector<std::size_t>`

Parameters

  groups | an output iterator with groups of segment indices

## ◆ target()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>

FT CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::target | ( | const std::size_t | i,
|  | const std::size_t | j
| ) |  | const

calculates the target value between 2 parallel segments, which are direct neighbors to each other.

The target value is the distance between two parallel segments `i` and `j`, where the distance is defined as the distance between the midpoint of the ith segment and the projection of this point onto the supporting line of the jth segment.

Parameters

  i | index of the first segment
  j | index of the second segment

Precondition
  i >= 0 && i < input_range.size()
  j >= 0 && j < input_range.size()

## ◆ unique_segments()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>
template<typename OutIterator >

OutIterator CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::unique_segments | ( | OutIterator | segments | ) | const

returns segments, which best-fit collinear groups.

This method first calls `Segments::collinear_groups()` and then substitutes each group of collinear segments by an average segment. The number of returned segments is the number of detected collinear groups.

Template Parameters

  OutIterator | a model of `OutputIterator` that accepts segments of type `GeomTraits::Segment_2`

Parameters

  segments | an output iterator with the simplified segments

## ◆ update()

template<typename GeomTraits , typename InputRange , typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2>>

void CGAL::Shape_regularization::Segments::Offset_regularization_2< GeomTraits, InputRange, SegmentMap >::update | ( | const std::vector< FT > & | solution | ) |

applies new positions computed by the `QuadraticProgramTraits` to the initial segments.

Number of values in `solution` equals to the number n of segments being regularized + the number m of neighbor pairs between these segments. Each of n values is an offset that is added to the initial segment position.

Parameters

  solution | a vector with offsets in unit lengths

Precondition
  solution.size() >= 1