Declarations

procedure Rotate(Alpha: TFloat); overload;
procedure Rotate(Cx, Cy, Alpha: TFloat); overload;

Overload Details

Overload 1

procedure Rotate(Alpha: TFloat); overload;

Rotates coordinates around the origin (0, 0) by Alpha degrees.

Parameter	Type	Description
Alpha	TFloat	Rotation angle in degrees.

Overload 2

procedure Rotate(Cx, Cy, Alpha: TFloat); overload;

Rotates coordinates around pivot point (Cx, Cy) by Alpha degrees.

Parameter	Type	Description
Cx, Cy	TFloat	Pivot point coordinates.
Alpha	TFloat	Rotation angle in degrees.

Description

Rotate multiplies the transformation matrix by a 2D rotation matrix for the specified angle in degrees.

At first, the origin is translated to (Cx, Cy), then an Alpha degree rotation is performed around the origin, and finally the origin is translated back.

$$M=\left[\begin{array}{ccc}\cos \alpha & \sin \alpha & 0\\ -\sin \alpha & \cos \alpha & 0\\ 0& 0& 1\end{array}\right]M;$$