Create openscad from construction image en

Create OpenSCAD from Construction Image

Converts a hand-drawn or photographed technical/construction sketch into a parametric OpenSCAD (.scad) file, ready for 3D printing or further CAD work.

When to use this skill

Activate when:

• The user uploads a photo or scan of a hand-drawn technical sketch.
• The user references a construction drawing with labeled dimensions.
• The user asks to convert a drawing, sketch, or annotation image into a 3D model.
• Dimension labels may be in English or German.

Typical trigger phrases:

• "Create OpenSCAD from this sketch / image / drawing / photo"
• "Generate .scad from this construction image"
• "Convert this drawing to OpenSCAD"
• "Make a CAD file / 3D model from this"
• "3D-printable file from this hand drawing"

Skills used (backreferences)

Skill	Repository	License
create-agent-skill-en	https://github.com/roebi/agent-skills	CC BY-NC-SA 4.0

This skill was scaffolded following the create-agent-skill-en workflow and specification from agentskills.io.

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Step-by-step workflow

1. Receive and inspect the image

• Accept the uploaded image (photo, scan, or screenshot of a technical sketch).
• Identify all labeled dimensions, annotations, and geometric shapes visible.
• Note the language of labels (English or German — see translation table below).

2. Extract dimensions and geometry

Read all visible dimension annotations. Common German labels and their meanings:

German label	English meaning	OpenSCAD parameter example
Länge	Length	length = ...;
Breite	Width	width = ...;
Höhe	Height	height = ...;
Durchmesser / Ø	Diameter	diameter = ...;
Radius	Radius	radius = ...;
Aussendurchmesser	Outer diameter	outer_diameter = ...;
Innendurchmesser	Inner diameter	inner_diameter = ...;
Innensechskant	Inner hex (across flats)	inner_hex_width = ...;
Wandstärke	Wall thickness	wall_thickness = ...;
Tiefe	Depth	depth = ...;
Bohrung	Bore / hole	bore_diameter = ...;
Schlüsselweite (SW)	Wrench size (hex flats)	hex_across_flats = ...;

Parse units (mm, cm, m) and convert all values to millimeters in the output.

3. Identify the primary shape

Determine the dominant geometry:

Shape in sketch	OpenSCAD primitive / pattern
Cylinder / round part	cylinder(h, d, $fn=64)
Box / rectangular block	cube([x, y, z])
Hex prism	cylinder(h, d=$fn=6) with adjusted diameter
Tube / hollow cylinder	difference() { cylinder(...outer...); cylinder(...inner...) }
Hex socket / Innensechskant	difference() { cylinder(outer); cylinder(hex, $fn=6) }
Cone / taper	cylinder(h, r1, r2)
Sphere	sphere(r)

For complex multi-feature parts, combine primitives using difference(), union(), or intersection().

4. Handle hex-across-flats conversion

When a hex is specified as across flats (Schlüsselweite / Innensechskant), OpenSCAD's cylinder($fn=6) uses the circumradius (across corners). Convert using:

d_circumradius = across_flats / cos(30)

In OpenSCAD:

// inner_hex_width = across-flats dimension
cylinder(h = length, d = inner_hex_width / cos(30), $fn = 6);

5. Write the OpenSCAD file

Structure the output file as follows:

// <Part name or description>
// Source: hand-drawn construction sketch
// Generated by: create-openscad-from-construction-image-en skill

// --- Parameters (all units: mm) ---
<parameter declarations with comments>

// --- Geometry ---
<OpenSCAD CSG model>

Rules:

• Declare all dimensions as named parameters at the top (easy editing).
• Add a comment on each parameter with its meaning and source label.
• Use $fn = 64 for smooth cylinders; $fn = 6 for hex prisms.
• Keep geometry readable — one operation per line, proper indentation.
• Add center = false or center = true explicitly to avoid ambiguity.

6. Output

• Provide the .scad file as a downloadable file named after the part.
• If the part name is unknown, use part.scad or derive from the dominant feature.
• Briefly summarize the interpreted dimensions in a table for user verification.

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Example: Hex Socket (from real sketch)

Sketch labels read:

• Innensechskant: 8mm
• Aussendurchmesser: 14mm Ø
• Länge: 25mm

Generated OpenSCAD:

// Hex Socket / Innensechskant
// Innensechskant (inner hex across flats): 8mm
// Aussendurchmesser (outer diameter): 14mm
// Länge (length): 25mm

outer_diameter = 14;   // mm — Aussendurchmesser
inner_hex_width = 8;   // mm — Innensechskant (across flats / Schlüsselweite)
length = 25;           // mm — Länge

difference() {
    // Outer cylinder
    cylinder(h = length, d = outer_diameter, center = false, $fn = 64);

    // Inner hexagon bore
    // d = across_flats / cos(30) converts SW to circumradius
    cylinder(h = length + 1, d = inner_hex_width / cos(30), center = false, $fn = 6);
}

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Ambiguity handling

If the sketch is unclear or dimensions are missing:

1. State which dimensions were successfully read.
2. List what is missing or ambiguous.
3. Use a placeholder variable with a comment: // TODO: verify this dimension.
4. Ask the user to confirm before finalizing.

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References

• references/openscad-primitives.md — Quick reference for OpenSCAD primitives and CSG operations
• references/german-dimension-labels.md — Extended German ↔ English dimension label glossary
• scripts-guide: https://raw.githubusercontent.com/roebi/agent-skills/refs/heads/main/skills/create-agent-skill-en/references/scripts-guide.md