Export Formats

vcad supports multiple export formats, each optimized for different use cases. This page explains the technical details of each format.

Format Overview

STL (Stereolithography)

The oldest and most universal format for 3D printing.

Format Details

• Binary STL — Compact, fast to read
• Triangle soup — No topology, just triangles
• No materials — Color/material not supported

vcad Implementation

pub fn write_stl(&self, path: &str) -> Result<(), CadError> {
    let mesh = self.manifold.to_mesh();
    let triangles = mesh_to_stl_triangles(&mesh);
    write_binary_stl(path, &triangles)
}

Binary STL structure:

[80 bytes header]
[4 bytes: triangle count]
[50 bytes per triangle]:
  - 12 bytes: normal (3 × f32)
  - 36 bytes: vertices (3 × 3 × f32)
  - 2 bytes: attribute (unused)

When to Use

• 3D printing (slicers require STL or 3MF)
• CNC machining
• Simple geometry transfer
• Maximum compatibility

glTF/GLB (Graphics Language Transmission Format)

Modern format for 3D graphics with PBR materials.

Format Details

• GLB — Binary container (JSON + buffers)
• PBR materials — Metallic-roughness workflow
• Multiple meshes — Scene graph support
• Widely supported — Three.js, Blender, web browsers

vcad Implementation

pub fn export_glb(
    part: &Part,
    material: &MaterialDef,
    path: &str,
) -> Result<(), CadError> {
    let mesh = part.manifold.to_mesh();
    let gltf = build_gltf_document(&mesh, material);
    write_glb(path, &gltf)
}

Material mapping:

// vcad MaterialDef → glTF pbrMetallicRoughness
{
    "baseColorFactor": [r, g, b, 1.0],
    "metallicFactor": metallic,
    "roughnessFactor": roughness
}

Multi-material Scenes

let mut scene = Scene::new("assembly");
scene.add(part_a, "steel");
scene.add(part_b, "rubber");
export_scene_glb(&scene, &materials, "assembly.glb")?;

Each part becomes a separate mesh node with its material.

When to Use

• Web viewers and interactive apps
• Blender/Unity/Unreal import
• Product visualization
• PBR material fidelity

USD (Universal Scene Description)

Pixar's format for complex scenes and simulation.

Format Details

• USDA — ASCII format (human-readable)
• USDC — Binary crate format
• Physics properties — Mass, friction, etc.
• Isaac Sim compatible — Robot simulation

vcad Implementation

pub fn export_usd(
    part: &Part,
    material: &MaterialDef,
    path: &str,
) -> Result<(), CadError> {
    let mesh = part.manifold.to_mesh();
    let usda = build_usda(&mesh, material);
    write_usda(path, &usda)
}

Physics attributes:

def "physics" {
    float physics:mass = 0.5
    float physics:density = 2700
    bool physics:rigidBodyEnabled = true
}

Robot Export

Special function for articulated robots:

pub fn export_robot_usd(
    body: &Part,
    wheels: &[Part],
    config: &RobotConfig,
    path: &str,
) -> Result<(), CadError>;

When to Use

• NVIDIA Isaac Sim
• Omniverse applications
• Physics simulation
• Film/VFX pipelines

DXF (Drawing Exchange Format)

2D vector format for CNC and laser cutting.

Format Details

• DXF R12 — Maximum compatibility
• 2D only — No 3D geometry
• Layers — Separate cut/score/bend lines
• ASCII — Human-readable

vcad Implementation

impl DxfDocument {
    pub fn add_rectangle(&mut self, w: f64, h: f64, cx: f64, cy: f64);
    pub fn add_circle(&mut self, cx: f64, cy: f64, r: f64);
    pub fn add_line(&mut self, x1: f64, y1: f64, x2: f64, y2: f64);
    pub fn add_bend_line(&mut self, x1: f64, y1: f64, x2: f64, y2: f64);
    pub fn export(&self, path: &str) -> Result<(), CadError>;
}

Layer organization:

• 0 — Default layer (cut lines)
• BEND — Bend lines for sheet metal

When to Use

• Laser cutting services
• CNC routing
• Sheet metal fabrication
• 2D profiles from 3D models

STEP (ISO 10303)

Industry standard for CAD data exchange.

Format Details

• AP214 — Automotive design
• B-Rep geometry — Exact surfaces, not meshes
• Full fidelity — Preserves design intent
• Requires OpenCASCADE — Heavy dependency

vcad Implementation

#[cfg(feature = "step")]
pub fn export_step(
    part: &Part,
    path: &str,
) -> Result<(), CadError> {
    let brep = mesh_to_brep(&part.manifold)?;
    write_step_ap214(path, &brep)
}

When to Use

• Professional CAD interchange
• Manufacturing documentation
• When exact geometry is required
• Regulatory compliance

Format Selection Guide

Need 3D printing?
  └─▶ STL

Need materials/visualization?
  └─▶ GLB

Need simulation?
  └─▶ USD

Need laser cutting?
  └─▶ DXF

Need CAD interchange?
  └─▶ STEP (if available)

Coordinate Systems

vcad uses a Z-up coordinate system (standard CAD convention):

• X — Right
• Y — Forward
• Z — Up
• Units — Millimeters (by convention)

The grid lies in the XY plane. Cylinder and cone primitives are created along the Z axis — already vertical, no rotation needed.

vcad does not transform coordinates on export — the model appears the same orientation in Z-up software (e.g., FreeCAD, most CAD tools). Y-up software (e.g., Blender default) may show the model on its side. The Three.js renderer internally applies a −90° X rotation to convert Z-up kernel data to Y-up display space.