CogEllipticalArc.SetFromUnitCircleParams Method

CogEllipticalArc SetFromUnitCircleParams Method

Cognex VisionPro

Set the geometry of this elliptical arc from the given description of a unit circular arc and the linear transform that maps it to an elliptical arc. The unit circle arc is centered at (0,0), has a radius of one, and has the given start angle (in radians) and span (in radians).

Namespace: Cognex.VisionPro
Assembly: Cognex.VisionPro.Core (in Cognex.VisionPro.Core.dll) Version: 65.1.0.0

Syntax

C++

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public void SetFromUnitCircleParams(
	double unitCircleAngleStart,
	double unitCircleAngleSpan,
	CogTransform2DLinear ellipseFromUnitCircle
)

public void SetFromUnitCircleParams(
	double unitCircleAngleStart,
	double unitCircleAngleSpan,
	CogTransform2DLinear ellipseFromUnitCircle
)

Public Sub SetFromUnitCircleParams ( 
	unitCircleAngleStart As Double,
	unitCircleAngleSpan As Double,
	ellipseFromUnitCircle As CogTransform2DLinear
)

Public Sub SetFromUnitCircleParams ( 
	unitCircleAngleStart As Double,
	unitCircleAngleSpan As Double,
	ellipseFromUnitCircle As CogTransform2DLinear
)

public:
void SetFromUnitCircleParams(
	double unitCircleAngleStart, 
	double unitCircleAngleSpan, 
	CogTransform2DLinear^ ellipseFromUnitCircle
)

public:
void SetFromUnitCircleParams(
	double unitCircleAngleStart, 
	double unitCircleAngleSpan, 
	CogTransform2DLinear^ ellipseFromUnitCircle
)

Parameters

unitCircleAngleStart: Type: System Double
The start angle of the unit circle arc in radians.

unitCircleAngleSpan: Type: System Double
The span of the unit circle arc in radians.

ellipseFromUnitCircle: Type: Cognex.VisionPro CogTransform2DLinear
The transform that maps the unit circle arc to this elliptical arc.

Events

Event Type	Reason
CogEllipticalArc Changed	Fires when the shape changes. The following state flags may be affected:

Event Type

Reason

CogEllipticalArc Changed

Fires when the shape changes.

The following state flags may be affected:

Exceptions

Exception	Condition
ArgumentException	unitCircleAngleSpan = 0.0.
ArgumentException	RadialScale <= 0.0 or RadialScale = 1.0.
ArgumentException	ellipseFromUnitCircle is NULL.

Remarks

Sets the geometry of this elliptical arc from the given description of a unit circular arc and the linear transform that maps it to an elliptical arc. The unit circle arc is centered at (0,0), has a radius of one, and has the specified start angle and span measured in radians.

Typically, the unitCircleAngleStart value is not the same as AngleStart, and the unitCircleAngleSpan is not the same as AngleSpan. The returned unitCircleAngleStart is normalized to be between +π and −π, but unitCircleAngleSpan is not.

The child space of this shape is unit circle space. In the unit circle child space, you can pick (x,y) positions along the arc using standard parametric equations for x and y:

x = cos(t) and y = sin(t)

where the angle t varies from unitCircleAngleStart and (unitCircleAngleStart + unitCircleAngleSpan).

You can map positions and angles in child space to the parent space using the ellipseFromUnitCircle transform. You can map from parent space to child space using the inverse transform.

Remember that AngleStart is measured from the x-axis of the ellipse. You must add Rotation to AngleStart to get the correct angle in parent space.