path2d_shapes.md

tagline
2D closed shapes

local shapes = require'path2d_shapes'

Drawing and other math for 2D closed shapes. All construction routines take a write consumer function which will be called as: write(command, args...).

Ellipses

shapes.ellipse_to_bezier3(write, cx, cy, rx, ry)

shapes.ellipse_bbox(cx, cy, rx, ry) -> left, top, width, height

Circles

shapes.circle_to_bezier3(write, cx, cy, r)

shapes.circle_to_bezier2(write, cx, cy, r[, segments])

shapes.circle_bbox(cx, cy, r) -> left, top, width, height

shapes.circle_length(cx, cy, r) -> length

shapes.circle_3p_to_bezier3(write, x1, y1, x2, y2, x3, y3)

Rectangles

shapes.rect_to_lines(write, x, y, w, h)

shapes.rect_to_straight_lines(write, x, y, w, h)

shapes.rect_bbox(x, y, w, h) -> left, top, width, height

shapes.rect_length(x, y, w, h) -> length

Rectangles with rounded corners

shapes.round_rect_to_bezier3(write, x, y, w, h, r)

shapes.round_rect_to_arcs(write, x, y, w, h, r)

shapes.round_rect_bbox(write, x, y, w, h, r)

shapes.round_rect_length(x, y, w, h, r) -> length

Rectangles with elliptic arc corners

shapes.elliptic_rect_to_bezier3(write, x, y, w, h, rx, ry)

shapes.elliptic_rect_to_elliptic_arcs(write, x, y, w, h, rx, ry)

shapes.elliptic_rect_bbox(x, y, w, h, rx, ry) -> left, top, width, height

Stars and Regular Polygons

shapes.rpoly_to_lines(write, cx, cy, x1, y1, n)

Construct a regular polygon with line segments. A regular polygon has a center, an anchor point and a number of segments.

shapes.star_to_star_2p(cx, cy, x1, y1, r2, n) -> cx, cy, x1, y1, x2, y2, n

Convert a simple star to a 2-anchor-point star. A simple star has a center, an anchor point, a secondary radius and a number of leafs. A 2-anchor-point star has a center, two anchor points and a number of leafs.

shapes.star_to_lines(write, cx, cy, x1, y1, r2, n)

Construct a star with line segments.

shapes.star_2p_to_lines(write, cx, cy, x1, y1, x2, y2, n)

Construct a 2-anchor-point star using line segments.

Formulas and the Superformula

shapes.formula_to_lines(write, formula, steps, ...)

Linearly interpolate a shape defined by a custom formula, and unite the points with line segments.

shapes.superformula(t, cx, cy, size, a, b, m, n1, n2, n3)

Return the point at time t (t covers the entire shape in the 0..1 range) on a superformula.

shapes.superformula_to_lines(write, cx, cy, size, steps, a, b, m, n1, n2, n3)

Construct a superformula by linear interpolation using steps number of line segments.