printa-modeling

name	printa-modeling
description	Create, revise, validate, preview, and export composable Printa Spec 1.0 JSON or YAML models through the Printa MCP server. Use for printable primitives, custom-curve extrusion, text, revolved profiles and vases, ordered deformation modifiers, assemblies, repeated forms, deterministic water surfaces, cloth drapes, editor previews, and STL output.

Printa procedural modeling

Build a complete Printa Spec 1.0 document, call create_procedural_model, inspect the returned bounds and warnings, then refine the spec until it matches the request.

Connect

Use the streamable HTTP MCP endpoint at https://printa.vochsel.com/mcp.

Read the machine schema at https://printa.vochsel.com/api/model/schema when exact field validation is needed. Read the spec reference for field semantics and the examples for reusable patterns.

Direct STL fallback

If the MCP server or MCP UI is not installed or does not return its tool result correctly, generate the same model without the plugin:

1. Complete and validate the full Printa JSON document locally.
2. UTF-8 encode the compact JSON and convert it to unpadded base64url.
3. Append it as spec to https://printa.vochsel.com/make/model.stl?spec=ENCODED_SPEC.
4. Return that URL as the direct binary STL download.

The endpoint evaluates the model when requested and returns Content-Type: model/stl. It also accepts a URL-encoded raw JSON or YAML document in spec, but base64url is preferred because punctuation survives chat clients and Markdown safely. Keep direct URLs comfortably below common URL-length limits; use the MCP tool or POST /api/model/stl for unusually large documents.

Model workflow

1. Translate the request into one source node or a small graph of nodes.
2. Choose document units and keep every dimensional value in those units.
3. Create the base form with primitive, extrude, revolve, text, water, or cloth.
4. Apply modifiers in intentional order. Modifier order changes the result.
5. Use assembly to merge distinct parts or repeat to make transformed copies.
6. Keep the graph compact. Prefer modifiers and repeats over enumerating many nodes.
7. Call create_procedural_model with the complete JSON or YAML document.
8. Inspect dimensions, triangle count, volume estimate, and warnings.
9. Refine the profile, amplitude, twist, resolution, wall, base/cap thickness, or transforms as needed.
10. Return both the unified Printa editor link (/editor) and STL link.

Choose a construction

• Use revolve for vases, vessels, knobs, bowls, columns, and any radial profile.
• Use extrude for badges, signs, trays, cutters, and custom 2D Bézier outlines.
• Use primitive for structural parts and assembly building blocks.
• Treat primitive width, depth, and height as exact outer bounds. For text, set height and depth for exact final dimensions and add width only when stretching or fitting to an exact width is intended.
• Use text for any Google-Font solid. Font, weight, case, italic, underline, bevel faces, smoothing, and curve resolution all belong in the source spec.
• Use extrudeSegments when text needs subdivisions through its depth, especially before deformations; curveSegments controls glyph outlines and bevelSegments controls rounded edges.
• Use water to freeze a deterministic damped-wave simulation into a solid tile.
• Use cloth to drape a thickened printable sheet over a spherical collider.
• Use repeat for radial-looking stacks, columns, ribs made from parts, and regular arrays.

Shape vases

Represent the silhouette as [radius, height] profile points in a revolve source. Set wall to create a hollow printable shell, keep bottomCap: true with a suitable bottomThickness for a usable vessel, and enable topCap only for sealed forms. Then:

• Add radialWave for flutes or lobes.
• Use radiusOffset to expand or contract every spun-profile radius without rewriting its control points.
• Add a modulation envelope to make flute or deformation amount vary over normalized height. Four keyframes are usually enough.
• Add twist after radialWave to turn those ribs into helices.
• Add taper after the ribs when the whole upper section should narrow.
• Use three or four large lobes for sculptural twists; use 12–24 shallow lobes for fine fluting.
• Keep the smallest inside radius larger than the wall.
• Use a solid base at least as thick as the wall; 2.4–3.2 mm is a practical FDM default.
• Use topThickness when topCap: true; open vases should keep topCap: false.
• Enable print.interiorStruts when a revolved shell needs an explicit printable internal truss. Choose diamond for general stiffness, cross for a lighter horizontal brace system, or radial for spokes around a center mast.
• Start around 16–24 mm spacing and 1.6–2.4 mm diameter for common FDM work, then adjust for scale and nozzle size.

Preserve printability

• Keep all dimensions positive and avoid zero-thickness parts.
• Use vessel walls of at least 1.2 mm for common FDM printers unless the user specifies another process.
• Keep repeated parts intersecting when they must print as one physical object.
• Treat assembly: merge as a shared STL containing its child solids; it does not perform a CAD boolean union.
• Check cloth output for steep overhangs and support requirements.
• Keep simulation resolution proportional to required physical detail; do not maximize it by default.
• Do not silently shrink forms that exceed the configured build volume. Return the warning and offer a revised spec.

Write promptable specs

• Use descriptive node ids such as outer-vessel, rim, or water-surface.
• Add a concise document description and metadata family.
• Set display.dimensions when W/H floor gizmos should be visible in the editor handoff.
• Set display.buildPlate: true when the editor should preview the configured print.buildVolume footprint.
• Prefer 4–9 profile control points and smooth interpolation over dense profiles.
• Use one modifier per conceptual change.
• Return a complete document beginning with version: "1.0"; never return a fragment unless explicitly requested.