﻿GetParameterAtPoint Method
Returns the value of the angle parameter for a point near or on the circumference of the ellipse.

Namespace:  ceometric.VectorGeometry
Assembly:  ceometric.VectorGeometry (in ceometric.VectorGeometry.dll) Version: 1.8.0.0 (1.8.0.0)

# Syntax

C#
```public double GetParameterAtPoint(
Point point
)```
Visual Basic (Declaration)
```Public Function GetParameterAtPoint ( _
point As Point _
) As Double```
Visual C++
```public:
double GetParameterAtPoint(
Point^ point
)```

#### Parameters

point
Type: ceometric.VectorGeometry..::.Point
A point.

#### Return Value

Returns the value of the parameter angle tetha for a point near or on the ellipse.

Returns 0.0 if point coincides with the center of the ellipse.

# Remarks

A point on the ellipse is defined by

p = c + a*cos(t) + b*sin(t), where

tetha
• t is the parameter angle tetha with t: [0, 2*pi]
• c is the center point of the ellipse.
• a is the semimajor axis vector of the ellipse.
• b is the semiminor axis vector of the ellipse.

In these terms, this function returns the ellipse parameter t for a given point p.

Use GetPointAtParameter(Double) to find the point p for a given ellipse parameter t

If p lies on the circumference of an ellipse e, then p = e.GetPointAtParameter(GetParameterAtPoint(p))

If point is coplanar to the ellipse but not on the circumference of the ellipse, this method returns the ellipse parameter t of the intersection point of the ellipse and the line through the center of the ellipse and point

Returns meaningless results if point is not coplanar to the ellipse!