CogEllipticalAnnulusSection.GetUnitCircleParams Method

CogEllipticalAnnulusSection GetUnitCircleParams Method

Cognex VisionPro 9.8

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

Namespace: Cognex.VisionPro
Assembly: Cognex.VisionPro.Core (in Cognex.VisionPro.Core.dll) Version: 75.1.0.0

Syntax

C++

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public void GetUnitCircleParams(
	out double unitCircleAngleStart,
	out double unitCircleAngleSpan,
	out double radialScale,
	out CogTransform2DLinear ellipseFromUnitCircle
)

public void GetUnitCircleParams(
	out double unitCircleAngleStart,
	out double unitCircleAngleSpan,
	out double radialScale,
	out CogTransform2DLinear ellipseFromUnitCircle
)

Public Sub GetUnitCircleParams ( 
	<OutAttribute> ByRef unitCircleAngleStart As Double,
	<OutAttribute> ByRef unitCircleAngleSpan As Double,
	<OutAttribute> ByRef radialScale As Double,
	<OutAttribute> ByRef ellipseFromUnitCircle As CogTransform2DLinear
)

Public Sub GetUnitCircleParams ( 
	<OutAttribute> ByRef unitCircleAngleStart As Double,
	<OutAttribute> ByRef unitCircleAngleSpan As Double,
	<OutAttribute> ByRef radialScale As Double,
	<OutAttribute> ByRef ellipseFromUnitCircle As CogTransform2DLinear
)

public:
void GetUnitCircleParams(
	[OutAttribute] double% unitCircleAngleStart, 
	[OutAttribute] double% unitCircleAngleSpan, 
	[OutAttribute] double% radialScale, 
	[OutAttribute] CogTransform2DLinear^% ellipseFromUnitCircle
)

public:
void GetUnitCircleParams(
	[OutAttribute] double% unitCircleAngleStart, 
	[OutAttribute] double% unitCircleAngleSpan, 
	[OutAttribute] double% radialScale, 
	[OutAttribute] 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.

radialScale: Type: System Double
The RadialScale of the unit circle's circular annulus section.

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

Remarks

Gets a description of this elliptical annulus section as a unit circular arc, a linear transform that maps it to an elliptical arc, and a radial scale. The unit circle arc is centered at (0,0), has a radius of one, and has the provided 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 start 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). To get points along the end arc, scale by RadialScale.

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.