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IArcEx Interface

GetPoint
GetRadius
SetRadius
IsValid
GetCenter
GetAngleRange
PassThroughPoint

The interface is implemented by Arcs. It allows calculation of additional properties associated with an arc. Basic properties of an arc can be accessed via IArc and ILine2D.

Before calling GetPoint, GetCenter or GetAngleRange methods of this interface the arc must be initialized.

See also Patchwork sampleInterface List


HRESULT GetPoint(double t, double* x, double* y)

Parameters

t - [in] Normalized Natural Parameter along the arc. t must be in range [0, 1]

x, y - [out] returned coordinates of the point

Remarks:

The method returns point at position t on the arc.


HRESULT GetRadius(double* r)

Parameters

r - [out, retval] Returned radius

Remarks:

The method is provided for convenience. It returns 1.0 / Curvature. When curvature is zero a large positive number ( 1.7E+308 ) is returned.


HRESULT SetRadius(double r)

Parameters

r - [in] New radius for the arc. See remarks below

Return Values

S_OK in case of success.

DISP_E_PARAMNOTOPTIONAL if r is 0

Remarks:

The method changes curvature Curvature to 1 / r. r must not be 0.  The method does no check validity of the resulting arc, assuming that further modifications may follow before usage of the arc object. If arc has been modified with this method the Init method below must be called prior calling any other methods of IArcEx.


HRESULT IsValid(VARIANT_BOOL *valid)

Parameters

valid - [out, retval] returned validity of the arc

Remarks:

The method returns true if the arc is valid.


HRESULT GetCenter(double* x, double* y)

Parameters

x, y - [out] The returned center of the arc

Remarks:

Calculates center of the arc. The arc must be valid and initialized


HRESULT GetAngleRange(double* a, double* b)

Parameters

a - [out] Polar angle of the first end.

b - [out] Polar angle of the second end.

Remarks:

TThe method returns polar angle (angle between radius towards a point and radius in positive direction ox x axis) of the first and the second end.


HRESULT PassThroughPoint(double x, double y, int* result)

Parameters

x,y - [in] Coordinates of point to lie on this arc

result - [out,retval] - result code. See remurks

Remarks:

TThe method modifies curvature of this arc so that the arc passes thourg the specified point. Returns: -1 the modification is impossible geometrically, but the curvature was been modified to the nearest valid value, 0 - the arc already contains the point and there were no changes, 1 - the arc was successfully modified