2D shapes#

Seven leaf blocks producing cross-sections. They take attributes and never contain other blocks.

2D shapes cannot be rendered on their own. Give them thickness with extrude or revolve first, or a part holding one fails with part "body" is 2D - extrude or revolve it before rendering.

A note on segments#

Several shapes take segments, the number of straight edges used to approximate a curve. 0 - the default - means let the kernel decide from its global quality settings, which setQuality controls. Set it explicitly when a specific facet count matters: a hole that must clear a printed bolt, or a preview that must stay cheap.

rect#

An axis-aligned rectangle.

rect { size = [40, 20] }
rect { size = [40, 20]  center = true }

Attributes#

rounded_rect#

A rectangle with true arcs at the corners.

rounded_rect { size = [62, 13]  radius = 6.5  center = true }

Attributes#

Caveats#

• Built by shrinking the rectangle and offsetting it back out, which is what makes each corner a true arc rather than a chamfer. A radius of 0 or less degenerates to a plain rect.
• size is the outer size. rounded_rect { size = [10, 10] radius = 5 } is a circle of diameter 10.

circle#

circle { radius = 12 }
circle { diameter = 24  segments = 64 }

Attributes#

Caveats#

• Give radius or diameter, never both: circle: give either "radius" or "diameter", not both. Both spellings exist because a drilled hole is specified by diameter and a fillet by radius, and converting at the call site is where mistakes happen.
• Always centred on the origin. There is no center attribute.

ellipse#

A circle scaled to two exact radii.

ellipse { radii = [30, 18] }

Attributes#

Caveats#

• Implemented as a scaled unit circle, so both radii stay exact rather than being approximated by a polygon fitted to an ellipse.
• Always centred. There is no center attribute - passing one is ellipse: unknown attribute "center".

regular_polygon#

An n-sided polygon, sized the way the part it represents is actually specified.

regular_polygon { sides = 6  width_across_flats = 5.5 }   // an M3 nut
regular_polygon { sides = 8  radius = 20  rotation = 22.5 }

Attributes#

Caveats#

• Give one sizing attribute. They are tried in the order above, so width_across_flats wins if several are present - do not rely on that; pass one.
• radius and diameter together are an error, as on circle.
• Fewer than 3 sides is an error: regular_polygon: "sides" must be at least 3.
• Always centred on the origin.
• With rotation = 0 the first corner is on +X. For a hexagon with flats on the X axis, use rotation = 30.

stadium#

A rectangle fully rounded on its short axis - the shape of a slot.

stadium { size = [40, 8]  center = true }

Attributes#

Caveats#

• The corner radius is always half the shorter side. That is what makes it a stadium rather than a rounded_rect that happens to look like one, and it means the ends are always semicircular however long it is.

polygon#

An explicit outline, or several contours.

polygon {
  points = [
    [0, 0], [26, 0], [24, 6], [16, 26],
    [14, 48], [18, 66], [22, 74], [0, 74],
  ]
}

Attributes#

Caveats#

• At least three points: polygon: "points" must be an array of at least 3 points.
• A nested list is read as several contours. [[0,0],[1,0],[1,1]] is one triangle; [[[0,0],…],[[2,2],…]] is two contours, which is how a shape with a hole is written without a separate difference.
• The outline should not self-intersect. The fill rule decides what happens when it does, rather than the shape being rejected.
• Points are not closed for you - the last point connects back to the first automatically, so do not repeat it.

Usage#

Profiles for revolving#

polygon is the workhorse for anything turned on a lathe. The profile is written in the XY plane with X as the radius and Y as the height, then revolved:

local profile = [
  [0, 0], [26, 0], [24, 6], [16, 26],
  [14, 48], [18, 66], [22, 74], [0, 74],
]

model "vase" {
  revolve { segments = 96  polygon { points = profile } }
}

Every X must be ≥ 0 - a profile that crosses the axis revolves through itself.

Slots and keyways#

stadium extruded is a slot; subtracted, it is a keyway:

difference {
  extrude { height = 6  rect { size = [60, 20]  center = true } }
  translate {
    offset = [0, 0, -1]
    extrude { height = 8  stadium { size = [40, 6]  center = true } }
  }
}

Hex sockets sized from the tool#

width_across_flats is the number printed on the key, so the model says what it means:

for i, size in [1.5, 2, 2.5, 3, 4, 5, 6] {
  translate {
    offset = [i * 8, 0, 0]
    extrude { height = 20  regular_polygon { sides = 6  width_across_flats = size + 0.3 } }
  }
}

The + 0.3 is print clearance - the language has no opinion about fits, so the model states them.

Holes without a boolean#

A second contour inside the first is a hole, which keeps a two-part profile as one shape:

polygon {
  fill_rule = "EvenOdd"
  points = [
    [[0, 0], [40, 0], [40, 30], [0, 30]],    // outline
    [[10, 10], [30, 10], [30, 20], [10, 20]], // hole
  ]
}

Troubleshooting#

part "body" is 2D - extrude or revolve it before rendering#

A 2D shape reached the renderer. Wrap it:

extrude { height = 4  circle { radius = 10 } }

"circle" is a shape and cannot contain other blocks#

A shape is a leaf. Something was nested inside its braces - usually a missing } on the line before, so the next block was swallowed.

circle: give either "radius" or "diameter", not both#

Pass one. They mean the same thing and accepting both would let a model disagree with itself.

circle: unknown attribute "segements"#

A typo. Every block rejects attributes it did not read, precisely so a misspelling fails loudly instead of silently rendering the default.

My rounded rectangle came out as a plain rectangle#

radius defaults to 1, which is invisible at most sizes, and it is clamped to half the shorter side. Check that it is set and that the shape is big enough to show it.

My hexagon is rotated 30° from what I wanted#

rotation = 0 puts a corner on +X. For a flat on +X, use rotation = 30 - or in general 180 / sides.