Offsets, cuts and sections

Method	Solid	Sketch	Returns
offset	✓	✓	the receiver’s kind
shell	✓	✓	the receiver’s kind
trim_by_plane	✓		Solid
split_by_plane	✓		Array of two Solids
slice	✓		Sketch
project	✓		Sketch
simplify	✓		Solid
decompose	✓		Array of Solids

offset

sketch.offset(delta = 1, join: :round, miter_limit: 2, segments: 0)
solid.offset(delta, segments: 0)

Grows the shape by delta on every side, or shrinks it by a negative one.

A Sketch’s corners follow join:. A miter reaches at most miter_limit times delta before it is squared off.

Parameter	Type	Default	Description
delta	Number	1	How far to grow; negative shrinks.
join	Symbol	:round	The corners: :round, :square, :miter or :bevel.
miter_limit	Number	2	With join: :miter only; at least 2.
segments	Number	0	Segments per full turn for round corners; 0 follows the resolution for a circle of radius delta.

A Solid’s offset is round all over: grown, it is the Minkowski sum with a sphere of radius delta, so every edge comes out rounded and the part grows by delta on every side. Shrunk, it is what is left once the space around it, grown by that sphere, is cut away: its outer edges stay sharp and its inner ones come out rounded. A Solid shrunk past its own thickness is empty. It takes no other join.

Returns: the receiver’s kind.

Raises: ValueError for a Solid’s delta of 0, or a Solid’s join: other than :round; ArgumentError for miter_limit: without join: :miter, or on a Solid.

puts square(10).offset(1, join: :miter).area     # 144
puts square(10).offset(-1).area                  # 64
puts cube(2).offset(0.2).bbox.min.inspect        # [-0.2, -0.2, -0.2]
puts cube(10).offset(-1).bbox.min.inspect        # [1, 1, 1]

shell

shape.shell(thickness, segments: 0)

Hollows the shape to walls thickness thick, keeping its outside: the shape less its offset by -thickness. A Sketch’s shell is the band along its outlines. A Solid’s is closed all round, so a difference cuts it open. Walls thicker than half the shape leave it whole.

Parameter	Type	Default	Description
thickness	Number	—	The wall thickness, greater than 0.
segments	Number	0	Segments per full turn for the rounded inner edges; 0 follows the resolution.

Returns: the receiver’s kind.

puts square(10).shell(1).area   # 36
cup = cylinder(r: 20, h: 30).shell(2) - cylinder(r: 30, h: 10).translate(z: 29)

trim_by_plane

solid.trim_by_plane(nx, ny, nz, offset = 0)
solid.trim_by_plane([nx, ny, nz], offset = 0)
solid.trim_by_plane(normal: [nx, ny, nz], offset: 0)
solid.trim_by_plane(nz: 1, offset: 4)

The part of the solid on the side of a plane that its normal points to. The plane has normal [nx, ny, nz] and lies offset along it from the origin. Given by keywords, a normal component left out is 0.

Parameter	Type	Default	Description
nx, ny, nz	Number	0	The plane’s normal. Also normal:, as an Array.
offset	Number	0	The plane’s distance from the origin along the normal.

Returns: Solid.

Raises: ArgumentError when no normal is given, or for normal: with nx:, ny: or nz:.

top = cube(10).trim_by_plane(0, 0, 1, 4)
puts top.bbox.z_min   # 4

split_by_plane

solid.split_by_plane(nx, ny, nz, offset = 0)

Both sides of a plane: [the side the normal points to, the other side]. The plane is given as for trim_by_plane; without a normal it is the YZ plane ([1, 0, 0]).

Returns: Array of two Solids. Either may be empty.

upper, lower = cube(10).split_by_plane(nz: 1, offset: 4)
puts upper.bbox.z_min   # 4
puts lower.bbox.z_max   # 4

slice

solid.slice(height = 0)

The cross-section of the solid at z = height, as a Sketch.

Returns: Sketch.

taper = square(10, center: true).extrude(10, scale: 0.5)
puts taper.slice(5).area   # 56.25: 7.5 × 7.5 halfway up

project

solid.project(cut: false)

The solid’s shadow on the XY plane, looking down z, as a Sketch. With cut: true it is the section at z = 0 instead, as slice(0).

Returns: Sketch.

footprint = sphere(5).translate(z: 20).project
puts footprint.bbox.x_size   # 10

simplify

solid.simplify(tolerance = nil)

A copy with fewer triangles: edges and corners whose removal moves the surface by no more than tolerance are collapsed, so flat regions merge. Without a tolerance it uses the one the part was made under (see Engine settings). The solid is computed at once.

Returns: Solid.

decompose

solid.decompose

The solid’s separate pieces, each a Solid of its own. The solid is computed at once.

Returns: Array of Solids.

pieces = (cube(2) + cube(2).translate(5, 0, 0)).decompose
puts pieces.size   # 2