Exception raised on validation failure (see invalid for reasons)

2-dimensional polygon

This type is kept private to force use of make, which performs validation by default, hopefully providing an early warning that the shape may have issues rendering in a CAD backend.

make ?validate ?holes outer

Create a 2d polygon from an outer path (perimeter), and zero or more holes (default = []). If validate is true (as it is by default), validation is performed, raising exceptions if the defined polygon is not simple (and thus, may cause problems in CGAL).

of_paths ?validate ps

Create a 2d polygon from a list of paths, with the outline first, followed by the inner hole paths (if any), e.g. (outer :: holes) as ps. See make for details.

of_list ps

Create a 2d polygon from a list of paths. Same as of_paths with ~validate:false.

to_list t

Convert the polygon t into a list with the outer path as the head.

add_holes ?validate ~holes t

Add holes to t. If validate is true (as it is by default), validation is performed, raising exceptions if the defined polygon is not simple (and thus, may cause problems in CGAL).

validation ?eps t

Validate that t is a legal polygon, without self-intersections within paths, cross-intersections between paths, or any duplicate points. All checks are performed with the tolerance eps. If valid, unit will be returned, otherwise an exception will be raised.

• raises InvalidPoly

  if any paths in t self-intersect, there are cross-intersections between them, or if there are duplicate points.

is_simple ?eps t

Return true if t is a simple polygon, without self-intersections within paths, cross-intersections between paths, or any duplicate points. All checks are performed with the tolerance eps.

circle ?fn ?fa ?fs r

Create a circle of radius r.

wedge ?fn ?fa ?fs ~centre ~radius ~start a

Create an arcing path (as in Path2.arc), with the centre point included to close the path, forming a wedge.

square ?center dims

Create a rectangular polygon with xy dims (e.g. width and height). If center is true then the path will be centred around the origin (default = false).

ellipse ?fn ?fa ?fs radii

Draw an ellipse with xy radii. The greater of the two radii is used for fragment/resolution calculation.

star ~r1 ~r2 n

Draw an n pointed star with inner radius r1 and outer radius r2.

ring ?fn ?fa ?fs ~thickness radii

Draw an empty elliptical ring of outer xy radii, with the given radial thickness (difference between outer and inner radii). For a circular ring, use equal x and y radii.

box ?center ~thickness dims

Create a rectangular empty box of outer xy dimensions dims, with the given xy thickness (difference between outer and inner xy dimensions). If center is true, then the path will be centred around the origin (default = false).

bbox t

Compute the 2d bounding box of the polygon t.

centroid ?eps t

Compute the centroid of the outer path of the polygon t. If t.outer is collinear or self-intersecting (within eps tolerance), an Invalid_argument exception is raised.

area ?signed t

Compute the total area of the polygon t. If signed is true, then the signed areas of the outer and holes paths of t will be summed (keep in mind that this is dependent on winding direction, which should generally be opposite between outer and inner paths), otherwise the unsigned (positive) area of the holes will be subtracted (default = false).

offset ?fn ?fs ?fa ?check_valid ?mode d t

Offset outer and inner paths of t by the specified distance d. The mode governs how d is used to create the new corners.

• `Delta will create a new outline whose sides are a fixed distance d (+ve out, -ve in) from the original outline (this is the default behaviour).
• `Chamfer fixed distance offset by d as with delta, but with corners chamfered.
• `Radius creates a new outline as if a circle of some radius d is rotated around the exterior (d > 0) or interior (d < 0) original outline. fn, fs, and fa parameters govern the number of points that will be used for these arcs (they are ignored for delta and chamfer modes).
• The check_valid default of `Quality 1 will check the validity of shifted line segments by checking whether their ends and n additional points spaced throughout are far enough from the original path. If there are no points that have been offset by the target d, a Failure exception will be raised. Checking can be turned off by setting this to `No.

map f t

Map the outer and inner paths of t with the function f.