Maintainer | diagrams-discuss@googlegroups.com |
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Two-dimensional ellipses (and, as a special case, circles).

- circle :: (Backend b R2, Renderable Ellipse b) => Diagram b R2
- ellipse :: (Backend b R2, Renderable Ellipse b) => Double -> Diagram b R2
- data Ellipse = Ellipse T2
- ellipseCenter :: Ellipse -> P2
- ellipseAngle :: Ellipse -> Rad
- ellipseAxes :: Ellipse -> (R2, R2)
- ellipseScale :: Ellipse -> (Double, Double)
- ellipseCoeffs :: Ellipse -> (Double, Double, Double, Double, Double, Double)

# Ellipse and circle diagrams

ellipse :: (Backend b R2, Renderable Ellipse b) => Double -> Diagram b R2Source

`ellipse e`

constructs an ellipse with eccentricity `e`

by
scaling the unit circle in the X direction. The eccentricity must
be within the interval [0,1).

# Mathematical ellipses

## Representation

An ellipse is represented by an affine transformation acting on the unit circle.

## Extracting attributes

ellipseCenter :: Ellipse -> P2Source

Compute the center of an ellipse.

ellipseAngle :: Ellipse -> RadSource

Compute the angle to the major axis of an ellipse, measured counterclockwise from the positive x axis in radians. The result will be in the range [0, tau/2).

ellipseAxes :: Ellipse -> (R2, R2)Source

Compute the vectors (va, vb) from the center of the ellipse to the edge of the ellipse along the major and minor axes. These vectors can lie in any quadrant, depending on how the ellipse has been transformed.

ellipseScale :: Ellipse -> (Double, Double)Source

Compute the scaling factors of an ellipse, i.e. (a,b) where a and b are half the lengths of the major and minor axes respectively.