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Public Member Functions
gp_GTrsf2d Class Reference

Defines a non persistent transformation in 2D space.
This transformation is a general transformation.
It can be a Trsf2d from package gp, an affinity, or you can
define your own transformation giving the corresponding
matrix of transformation.

With a GTrsf2d you can transform only a doublet of coordinates
XY. It is not possible to transform other geometric objects
because these transformations can change the nature of non-
elementary geometric objects.
A GTrsf2d is represented with a 2 rows * 3 columns matrix :

V1 V2 T XY XY
| a11 a12 a14 | | x | | x'|
| a21 a22 a24 | | y | | y'|
| 0 0 1 | | 1 | | 1 |

where {V1, V2} defines the vectorial part of the
transformation and T defines the translation part of
the transformation.
Warning
A GTrsf2d transformation is only applicable on
coordinates. Be careful if you apply such a
transformation to all the points of a geometric object,
as this can change the nature of the object and thus
render it incoherent!
Typically, a circle is transformed into an ellipse by an
affinity transformation. To avoid modifying the nature of
an object, use a gp_Trsf2d transformation instead, as
objects of this class respect the nature of geometric objects.

#include <gp_GTrsf2d.hxx>

Public Member Functions

DEFINE_STANDARD_ALLOC gp_GTrsf2d ()
 returns identity transformation.

 gp_GTrsf2d (const gp_Trsf2d &T)
 Converts the gp_Trsf2d transformation T into a
general transformation.

 gp_GTrsf2d (const gp_Mat2d &M, const gp_XY &V)
 Creates a transformation based on the matrix M and the
vector V where M defines the vectorial part of the
transformation, and V the translation part.

void SetAffinity (const gp_Ax2d &A, const Standard_Real Ratio)
 Changes this transformation into an affinity of ratio Ratio
with respect to the axis A.
Note: An affinity is a point-by-point transformation that
transforms any point P into a point P' such that if H is
the orthogonal projection of P on the axis A, the vectors
HP and HP' satisfy: HP' = Ratio * HP.

void SetValue (const Standard_Integer Row, const Standard_Integer Col, const Standard_Real Value)
 Replaces the coefficient (Row, Col) of the matrix representing
this transformation by Value,
Raises OutOfRange if Row < 1 or Row > 2 or Col < 1 or Col > 3

void SetTranslationPart (const gp_XY &Coord)
 Replacesthe translation part of this
transformation by the coordinates of the number pair Coord.

void SetTrsf2d (const gp_Trsf2d &T)
 Assigns the vectorial and translation parts of T to this transformation.

void SetVectorialPart (const gp_Mat2d &Matrix)
 Replaces the vectorial part of this transformation by Matrix.

Standard_Boolean IsNegative () const
 Returns true if the determinant of the vectorial part of
this transformation is negative.

Standard_Boolean IsSingular () const
 Returns true if this transformation is singular (and
therefore, cannot be inverted).
Note: The Gauss LU decomposition is used to invert the
transformation matrix. Consequently, the transformation
is considered as singular if the largest pivot found is less
than or equal to gp::Resolution().
Warning
If this transformation is singular, it cannot be inverted.

gp_TrsfForm Form () const
 Returns the nature of the transformation. It can be
an identity transformation, a rotation, a translation, a mirror
transformation (relative to a point or axis), a scaling
transformation, a compound transformation or some
other type of transformation.

const gp_XYTranslationPart () const
 Returns the translation part of the GTrsf2d.

const gp_Mat2dVectorialPart () const
 Computes the vectorial part of the GTrsf2d. The returned
Matrix is a 2*2 matrix.

Standard_Real Value (const Standard_Integer Row, const Standard_Integer Col) const
 Returns the coefficients of the global matrix of transformation.
Raised OutOfRange if Row < 1 or Row > 2 or Col < 1 or Col > 3

Standard_Real operator() (const Standard_Integer Row, const Standard_Integer Col) const
void Invert ()
gp_GTrsf2d Inverted () const
 Computes the reverse transformation.
Raised an exception if the matrix of the transformation
is not inversible.

void Multiply (const gp_GTrsf2d &T)
void operator*= (const gp_GTrsf2d &T)
gp_GTrsf2d Multiplied (const gp_GTrsf2d &T) const
 Computes the transformation composed with T and <me>.
In a C++ implementation you can also write Tcomposed = <me> * T.
Example :
GTrsf2d T1, T2, Tcomp; ...............
//composition :
Tcomp = T2.Multiplied(T1); // or (Tcomp = T2 * T1)
// transformation of a point
XY P(10.,3.);
XY P1(P);
Tcomp.Transforms(P1); //using Tcomp
XY P2(P);
T1.Transforms(P2); //using T1 then T2
T2.Transforms(P2); // P1 = P2 !!!

gp_GTrsf2d operator* (const gp_GTrsf2d &T) const
void PreMultiply (const gp_GTrsf2d &T)
 Computes the product of the transformation T and this
transformation, and assigns the result to this transformation:
this = T * this

void Power (const Standard_Integer N)
gp_GTrsf2d Powered (const Standard_Integer N) const
 Computes the following composition of transformations
<me> * <me> * .......* <me>, N time.
if N = 0 <me> = Identity
if N < 0 <me> = <me>.Inverse() *...........* <me>.Inverse().

Raises an exception if N < 0 and if the matrix of the
transformation is not inversible.

void Transforms (gp_XY &Coord) const
gp_XY Transformed (const gp_XY &Coord) const
void Transforms (Standard_Real &X, Standard_Real &Y) const
 Applies this transformation to the coordinates:

gp_Trsf2d Trsf2d () const
 Converts this transformation into a gp_Trsf2d transformation.
Exceptions
Standard_ConstructionError if this transformation
cannot be converted, i.e. if its form is gp_Other.

const gp_Mat2d_CSFDB_Getgp_GTrsf2dmatrix () const
const gp_XY_CSFDB_Getgp_GTrsf2dloc () const
gp_TrsfForm _CSFDB_Getgp_GTrsf2dshape () const
void _CSFDB_Setgp_GTrsf2dshape (const gp_TrsfForm p)
Standard_Real _CSFDB_Getgp_GTrsf2dscale () const
void _CSFDB_Setgp_GTrsf2dscale (const Standard_Real p)

Constructor & Destructor Documentation


Member Function Documentation

Standard_Real gp_GTrsf2d::operator() ( const Standard_Integer  Row,
const Standard_Integer  Col 
) const [inline]
gp_GTrsf2d gp_GTrsf2d::operator* ( const gp_GTrsf2d T) const [inline]
void gp_GTrsf2d::operator*= ( const gp_GTrsf2d T) [inline]
void gp_GTrsf2d::Transforms ( gp_XY Coord) const
  • of the number pair Coord, or
  • X and Y.

    Note:
  • Transforms modifies X, Y, or the coordinate pair Coord, while
  • Transformed creates a new coordinate pair.

The documentation for this class was generated from the following file: