Jj openscad lite skill

OpenSCAD Code Generation Skill (Lite)

CRITICAL RULE: NO TOOLS

Do NOT use any external tools, linters, compilers, renderers, or validation checks when generating OpenSCAD code. Do NOT run openscad CLI, linters, renderers, or build systems. Generate code purely from knowledge.

How to Write OpenSCAD Code

OpenSCAD is a declarative, functional 3D compiler — not an interactive modeller. Code describes geometry; the engine renders it. Key principles:

1. Parametric by default — use variables, not magic numbers
2. Modules for reuse — encapsulate geometry in named modules with parameters
3. CSG composition — build complex shapes from primitives via union, difference, intersection
4. 2D → 3D pipeline — define 2D profiles, extrude to 3D
5. Functional style — prefer list comprehensions and functions over imperative loops

Quick Reference

For detailed information on any topic, read the corresponding section in the single combined reference file:

Topic	Section in references/reference.md
Language syntax, variables, types, operators, control flow	Language Reference
3D primitives, transformations, CSG, boolean operations	3D Modeling
2D primitives, extrusion, text, projection, import/export	2D Subsystem
List comprehensions, modules, children, recursion, special vars	Advanced Features
Parametric design patterns, reusable libraries, best practices	Tips and Patterns

Core Syntax at a Glance

// Variables (immutable, no reassignment)
width = 10; height = 20; name = "bracket";

// Conditional assignment / ternary
x = (width > 5) ? 10 : 20;

// Function literal
f = function(x) x * 2;

// Module definition
module my_box(w, h, d) { cube([w, h, d], center = true); }

// Function definition
function add(a, b) = a + b;

// Include vs Use
include <lib.scad>   // imports code, executes top-level statements
use <lib.scad>       // imports modules/functions only

Primitives

// 3D
sphere(r = 10);  sphere(d = 20);
cube([10, 20, 30], center = true);  cube(10);  // shorthand
cylinder(h = 20, r = 5, center = true);
cylinder(h = 20, r1 = 10, r2 = 5);  // truncated cone
polyhedron(points = [...], faces = [...]);

// 2D
circle(r = 10);  circle(d = 20);
square([10, 20], center = true);
polygon(points = [[0,0], [10,0], [5,10]]);
text("Hello", size = 10, font = "Liberation Sans");

Transformations

translate([x, y, z]) { ... }
rotate([x, y, z]) { ... }            // Euler angles (degrees)
rotate(a = 45, v = [0, 0, 1]) { ... } // axis-angle
scale([x, y, z]) { ... }
mirror([1, 0, 0]) { ... }            // mirror across YZ plane
resize([x, y, z]) { ... }
color("red", alpha = 0.5) { ... }
color([1, 0, 0, 0.5]) { ... }        // RGBA 0-1
multmatrix(m) { ... }                // 4x4 transform matrix
offset(r = 2) { ... }                // 2D: round offset
offset(delta = 2, chamfer = true) { ... }  // 2D: chamfered
hull() { ... }                       // convex hull
minkowski() { ... }                  // Minkowski sum (expensive)

Boolean / CSG Operations

union() { ... }                    // default if not specified
difference() { body(); holes(); }
intersection() { ... }

Extrusion

linear_extrude(height = 10, center = true, twist = 90, slices = 50, scale = 0.5) {
    circle(r = 5);
}
rotate_extrude(angle = 270, $fn = 100) {
    translate([10, 0, 0]) circle(r = 2);  // must be in positive X half-plane
}

Control Flow

// For loop (geometry context — no break/continue)
for (i = [0:10]) { translate([i*5, 0, 0]) cube(3); }
for (i = [0:2:10]) { ... }         // step of 2
for (i = [1, 3, 7, 9]) { ... }    // explicit list
for (i = list, j = list2) { ... }  // nested (parallel)

// If statement (no else-if chain; use ternary)
if (condition) { ... }
if (condition) { ... } else { ... }

// Let statement (creates new scope)
let (x = 5, y = 10) { ... }

// Intersection for
intersection_for(i = [0:5]) { ... }

List Comprehensions

[for (i = [0:10]) i * 2]                    // generate
[for (i = [0:10]) if (i % 2 == 0) i]        // filter
[for (a = list1) each a]                     // flatten
[for (i = [0:10]) let (x = i*2) x + 1]      // let binding
[for (i = [0:3]) for (j = [0:3]) [i, j]]    // nested (product)

Special Variables

Variable	Purpose
$fa	Minimum angle (degrees) for circle resolution
$fs	Minimum size (mm) for circle resolution
$fn	Fixed number of segments for circles
$t	Animation step (0-1)
$vpr, $vpt, $vpd, $vpf	Viewport rotation, translation, distance, FOV
$preview	true in preview (F5), false in render (F6)
$children	Number of children in a module

Modifier Characters

Prefix	Name	Effect
*	Disable	Disable the object
!	Root	Show only this object (and its children)
#	Debug	Highlight/transparent debug view
%	Background	Show as transparent background

Built-in Functions

• Math: abs, sign, sin, cos, tan, acos, asin, atan, atan2, floor, round, ceil, ln, log, pow, sqrt, exp, rands, min, max, norm, cross
• Type test: is_undef, is_bool, is_num, is_string, is_list, is_function
• List/String: len, concat, str, chr, ord, search, lookup
• Other: echo, assert, render, children, version, version_num, parent_module
• Constants: undef, PI

Import/Export

// Import 2D: import("file.dxf"), import("file.svg")
// Import 3D: import("file.stl", convexity = 10), .off, .amf, .3mf
// Surface:   surface(file = "data.dat", center = true), surface(file = "image.png")
// Export is done via GUI or CLI: -o output.stl

Best Practices

1. Always use center = true on primitives when building centered assemblies
2. Use $fn, $fa, $fs per-object, not globally
3. Prefer use <lib.scad> over include when you only need modules/functions
4. Name parameters explicitly: cylinder(h = 10, r = 5) not cylinder(10, 5)
5. Use assert() for parameter validation
6. Use $preview to switch between fast preview and full render geometry
7. Use modifier characters (#, %) for debugging without modifying code
8. Keep modules small and composable — one module = one logical part
9. Use list comprehensions instead of imperative for-loops for data transformation
10. Document with comments — OpenSCAD has no docstring convention

For detailed patterns, advanced examples, and complete worked designs, read references/reference.md.