Cheat Sheet

Print this out and keep it handy. Probably.

Primitives

3D

Position convention: box/cylinder/sphere/cone/torus are centered at the origin. extrude h is bottom-aligned (z=0..h). When mixing both, use | floor / translate / center:(true,true,false) to align them.

2D

sketch segments: tuple = line, arc start through end = 3-point arc, arc start end center:(cx,cy) = center arc, arc start end radius:radius = radius arc, bezier [control points] = Bezier (start point is implicit from the preceding segment; list contains control points and the end point), spline [through points] = spline (likewise). First element is the start point; auto-close.

Paths

wire is the open version of sketch (no auto-close). Joins multiple segments into an open wire. Supports both 2D and 3D coordinates. Ideal as the spine (upstream) of sweep. Its type is Wire (a curve): it never becomes a face even when closed, so extrude/cut/2D booleans reject it; offset d turns it into a Face of width 2|d|. sketch, rect and the other 2D primitives are Faces:

wire [(0,0), (10,0), arc (10,0) (15,5) radius:5] | sweep (circle 5)

Like sketch, wire works with workplane to draw on any plane:

workplane XZ | wire [(0,0),(10,0),(10,10),(0,10),(0,0)] | sweep (circle 2)

Pipe Operations

Modifiers

A wire of one straight segment (two points) cannot be offset. It fails with offsetWire2D: operation failed. Add a midpoint to make it two segments and it works: wire [(0,0),(20,0),(40,0)].

Boolean

Pipe operation: box 10 10 10 | diff (sphere 7) Source command: union [box 10 10 10, sphere 7] / diff [...] / inter [...] Shape operators: a + b (union) / a - b (diff) / a * b (inter). Only between variables or parentheses: (box 10 10 10) - (cylinder 3 20) works, box 10 10 10 - cylinder 3 20 is a parse error (it collides with argument arithmetic). base - holes | fillet 2 is (base - holes) | fillet 2. Parenthesise when mixing * with +/-

Place

Place a 2D shape stored in a variable onto a face, then cut or extrude:

$s = sketch [(5,0), arc (5,0) (0,-5) (-5,0), (0,7), (5,0)]
box 10 10 10 | faces >Z | place $s | cut

2D → 3D

Machining

Transform

translate, rotate, scale accept origin: keyword: "world" (default), "local" (bbox center), or (x,y,z).

A 2D shape cannot leave the workplane it was drawn on. To put a path or an outline on a vertical plane (XZ / YZ), draw it there to begin with, or write it in 3D coordinates – do not try to stand it up with rotate:

workplane XZ | wire [arc (0,-25) (25,0) center:(0,0)] | sweep (circle 5)   # arc on the XZ plane
arc (0,0,-25) (25,0,0) center:(0,0,0) | sweep (circle 5)                   # the same path in 3D

rotate 0 0 45 origin:"local"    # rotate around object center
scale 2 origin:(10, 0, 0)       # scale from arbitrary point

Selection and Workplane

Selection

| faces sel        # select faces
| edges sel        # select edges
| verts sel        # select vertices (in 2D, returns shape vertices; can place 2D/3D primitives)
| verts | translate x y z   # offset vertex positions (stays in selection)
| points [...]     # specify points by coordinates
| points (polar n r)     # circular arrangement
| points (grid nx ny p)  # grid arrangement
| points ... | translate x y z  # offset point positions (stays in selection)

After face selection, polar / grid can be written directly (omitting points):

| faces top | polar 6 20 | hole 3     # same as points (polar 6 20)
| faces top | grid 2 3 20 | hole 3    # same as points (grid 2 3 20)

Selector symbols

Only >Z selects a single face. =Z and +Z come back as two faces and four (for a 60x40x30 box, areas 4800 and 6000).

Name aliases

Compound selectors

| edges >Z >X          # AND: Z-max AND X-max
| edges [>Z, <Z]       # OR: Z-max OR Z-min

Tagging (as)

| faces <X as $left     # name a face for later reference
| edges =Z as $top_edges

Workplane

| faces top | rect 50 30      # draw 2D directly from face selection (implicit workplane)
| faces top | workplane XZ    # use workplane only when you need a specific axis

Placement at:

at: is a named argument. Omit parentheses for simple coordinates. Parentheses are required for expressions.

cylinder 2.5 10 at:20 10                 # single position (omit parentheses)
cylinder 2.5 10 at:(20, 10)              # parenthesized form also valid
cylinder 2.5 10 at:[(0,0), (20,10)]      # list (brackets required)
rect 10 5 angle:45                       # rotation (angle: named argument)
box 10 10 3 | polar 6 20                 # circular array (3D context)
box 10 10 3 | grid 4 3 20               # grid array (3D context)

In a face selection context, polar/grid are interpreted as points:

box 10 10 10 | faces top | polar 6 20 | circle 3 | cut   # circular point arrangement
box 10 10 10 | faces top | grid 2 3 20 | circle 3 | cut  # grid point arrangement

Syntax

Variables

$w = 80
box $w $w/2 10

Function definition

def name($args) = pipeline

Import

import "gear"

Conditional expression

if $x > 0 then $x else -$x

List comprehension

[$i * 10 for $i in range(6)]

Operators (highest to lowest precedence)

** → * / // % → + - → comparison → and → or → |

CLI

The common ones. Every subcommand and option is in the CLI reference.

-D type inference: 100 -> int, 1.5 -> float, true/false -> bool, anything else -> string

When -D and --params-file are combined, -D wins. Precedence: -D > --params-file > @param defaults

poly build box.poly -D width=100 -D height=50
poly build box.poly --params-file presets/small.json -D width=120

Sections: poly section

Cut the model with a plane and report the contours. This is for checking a shape by numbers rather than by looking at a picture.

poly section m.poly                      # default xz,yz (through the bbox centre)
poly section m.poly --plane Z=10         # an explicit position
poly section m.poly --plane xz,yz,Z=10   # several
poly section m.poly --plane Y=0 -o cut.svg

Name a plane by the two axes it contains (xz has a Y normal). Omit the position and it passes through the centre of the bounding box.

section XY @ Z=20: 2 loops
  loop 0: closed  bbox 39.999x39.9995 at (...)  area 1256.6371  length 125.6637  points 315
  loop 1: closed  bbox 15.999x15.9995 at (...)  area 201.0619   length 50.2655   points 199

Two loops mean hollow, one means solid. area and length are exact, measured off the analytic curves (above is a 40mm cylinder with a 16mm bore, matching pir^2 and 2pi*r to the digit). bbox and points come from the sampled drawing path, so on a curved face they sit fractionally inside. An area prefixed with ~ means no face could be built and the polygon area was returned instead.

The SVG written by -o has path coordinates in millimetres, with the display scale kept in a group transform. A 2mm floor and 2mm wall can be read straight out of d="M 45.25 0 L 15 0 L 15 2 ...".

Context Transitions

3D ─→ faces/edges ─→ 2D ─→ extrude/cut ─→ 3D
              │        │
              │        └── hole ──→ 3D (hole at face center)
              │
              └── fillet/chamfer ──→ 3D

Face/Wire ─→ verts ──→ 2D primitive ─→ Face/Wire
       │    └─→ 3D primitive ─→ 3D
       │    └─→ translate ─→ verts (offset and stay in selection)
       │
points ──→ hole ──→ 3D (hole at each point)
       └─→ translate ─→ points (offset and stay in selection)

Remember: create → select → draw → return (workplane is optional – just select a face and draw directly)

With verts, both 2D and 3D primitives can be placed at each vertex. Use translate to offset positions before placement:

rect 100 100 | verts | circle 1      # place circles at each vertex → 2D
rect 100 100 | verts | box 1 1 1     # place boxes at each vertex → 3D
rect 80 60 | verts | translate 10 10 10 | cone 2 0 6   # offset vertices then place