StepVisualizer

A WebAssembly-based 3D STEP file visualizer built with Rust and WebGPU. This tool parses and renders STEP files directly in the browser (CSR).

Live Demo

Environment	URL	Updated on
Testing	https://mtb0x1.github.io/stepvisualizer/testing/	Push/PR master -> testing merged
Production	https://mtb0x1.github.io/stepvisualizer/production/	Push/PR testing -> release merged

A landing page at https://mtb0x1.github.io/stepvisualizer/ links to both environments.

To enable verbose tracing, append ?tracing=on&level=trace to either URL and check the browser console.

Current Status

This is an experimental project.

The visualization works for basic STEP files but may fail or crash with complex models.

Performance and stability are not guaranteed.

Supported STEP Formats

All files must be encoded as ISO-10303-21 (the standard physical file format for STEP, .stp / .step extension). The visualizer uses ruststep for parsing and truck-stepio for geometry extraction. Support level depends on the FILE_SCHEMA declared in the file header.

Note

The examples/ directory intentionally includes files from unsupported or partially-supported schemas. They are provided so users can load them, observe the current behaviour, and help track what still needs work. Do not assume a file renders correctly just because it ships with the project.

Schema / Standard	Common Name	ISO Code	Supported	Geometry rendered	Part hierarchy	Color from file	PMI / GD&T	Multi-body assemblies
CONFIG_CONTROL_DESIGN	AP203 (ed.1)	ISO 10303-203	Yes	Yes	No	No*	No	~
AUTOMOTIVE_DESIGN	AP214 (ed.1–3)	ISO 10303-214	Yes	Yes	No	Yes	No	~
AP203_E2 / CONFIGURATION_CONTROL_3D_DESIGN_ED2	AP203 ed.2	ISO 10303-203	~	~	No	Yes	No	~
AP242_MANAGED_MODEL_BASED_3D_ENGINEERING	AP242	ISO 10303-242	~	~	No	Yes	No	~
FEATURE_BASED_PROCESS_PLANNING	AP224	ISO 10303-224	No	No	No	No	No	No
STRUCTURAL_ANALYSIS_DESIGN / AP209	AP209	ISO 10303-209	No	No	No	No	No	No
PLANT_SPATIAL_CONFIGURATION	AP221	ISO 10303-221	No	No	No	No	No	No
SHIP_STRUCTURES_SCHEMA	AP218	ISO 10303-218	No	No	No	No	No	No

Yes Supported, ~ Partial, No Not supported
* AP203 ed.1 (CONFIG_CONTROL_DESIGN) does not define presentation/color entities in its schema standard; fallback palette is used.

Feature Notes

What works (AP203 / AP214):

• B-Rep solid geometry (BSpline surfaces, planes, cylinders, cones, tori, …) is tessellated via truck's triangulation pipeline.
• Surface and part colors: extracted from presentation styles (STYLED_ITEM, OVER_RIDING_STYLED_ITEM, COLOUR_RGB, DRAUGHTING_PRE_DEFINED_COLOUR, SURFACE_STYLE_USAGE / SURFACE_STYLE_RENDERING_WITH_PROPERTIES) and rendered per-part in WebGPU and the hierarchy/meshes panel; fallback deterministic cycling palette is applied when colors are absent.
• Basic header metadata is displayed (filename, timestamp, author, schema, entity count, bounding box, units).
• Volume and surface area can be computed on demand from the tessellated mesh.
• Files with multiple DATA sections are processed (all usable sections are merged).
• Unit systems: SI_UNIT prefixes (mm, cm, m, km) and CONVERSION_BASED_UNIT (inch, foot) are recognized.

Known gaps even for supported schemas:

• Part/assembly hierarchy: the product tree (PRODUCT, NEXT_ASSEMBLY_USAGE_OCCURENCE, …) is not parsed - each shell is treated as a flat, independent part.
• Complex appearance & textures: Face-level texture coordinates, PBR textures, and advanced optical material properties (e.g. subsurface scattering, refraction index) are not parsed; diffuse surface color and alpha transparency are supported.
• PMI / GD&T annotations: datum targets, geometric tolerances, and annotation planes are ignored.
• 2D geometry: GEOMETRIC_CURVE_SET and wire-body entities produce no triangles and are silently skipped.
• Complex shells: shells that fail truck's compression step are skipped with a warning; the rest of the file is still rendered.
• Large files: files larger than the configured limit are rejected; very large models may be slow or cause the browser tab to run out of memory.

Why AP224 / AP209 / AP218 / AP221 are not supported: These schemas contain domain-specific entity types (machining features, FEA meshes, piping layouts, ship structure panels) that have no geometry representation in truck-stepio's Table. The parser accepts the ISO-10303-21 envelope but produces zero renderable shells.

Features

• Web-based 3D visualization of STEP files
• View part hierarchy and metadata
• WebGPU-accelerated rendering
• Works entirely in the browser (no server processing)

sequenceDiagram
    participant User
    participant App as App (lib.rs)
    participant Workspace as Workspace Hook
    participant Storage as Storage
    participant Render as Render Module
    participant Camera as Camera
    participant Canvas as WebGPU Canvas

    User->>App: Load STEP file
    App->>Workspace: on_file_change callback
    Workspace->>Storage: Read and hash file
    Workspace->>Render: extract_render_parts
    Note over Render: Tessellate → vertices/indices
    Render->>Storage: Cache render parts
    Workspace->>App: Update metadata, step_model
    App->>MainPanel: Pass step_model
    MainPanel->>Camera: compute_eye_position
    Camera-->>MainPanel: Eye position [x, y, z]
    MainPanel->>Canvas: render_wgpu_on_canvas
    Canvas->>Canvas: Render pass, draw calls
    Canvas-->>User: Display geometry

Loading

Requirements

• A modern browser with WebGPU support : check https://caniuse.com/?search=webgpu
• Enable WebGPU in the browser (Chrome: chrome://flags/#enable-webgpu, Firefox: about:config -> webgl.webgpu.force-enabled)

Getting Started

1. Install prerequisites:

   rustup target add wasm32-unknown-unknown
   cargo install trunk

2. Run the development server:

   trunk serve

   or build the standalone WASM bundle (use ./ for local dev, a sub-path for subdirectory deployments):

   trunk build --release --public-url ./

3. Open http://localhost:8080 in a WebGPU-capable browser

Running Tests

Unit tests run in a freestanding wasm32-unknown-unknown browser environment with WebAssembly SIMD (+simd128,+relaxed-simd) enabled via wasm-pack test:

# Headless Chrome / Chromium (Local & CI/CD)
wasm-pack test --headless --chrome

# Or using Firefox
wasm-pack test --headless --firefox

Example Files

The examples/ directory ships with a variety of real-world STEP files spanning multiple schemas. Not all of them render correctly - this is intentional. They serve as a test bed to explore current support and surface gaps.

File	Schema	Renders?
Part1.stp	CONFIG_CONTROL_DESIGN (AP203)	Yes
nasty_cheese.stp	CONFIG_CONTROL_DESIGN (AP203)	Yes
l44mji.step	CONFIG_CONTROL_DESIGN (AP203)	Yes
as1-tc-214.stp	AUTOMOTIVE_DESIGN (AP214)	Yes
io1-ca-214.stp	AUTOMOTIVE_DESIGN (AP214)	Yes
io1-tc-214.stp	AUTOMOTIVE_DESIGN (AP214)	Yes
boxy_with_cylindricity.stp	AUTOMOTIVE_DESIGN (AP214)	Yes
d2-db-214.stp	AUTOMOTIVE_DESIGN (AP214)	Yes
Cruise_Assembly.stp	AUTOMOTIVE_DESIGN (AP214)	~
Rocky_House.stp	AUTOMOTIVE_DESIGN (AP214)	~
twr_ps_16.stp	SHIP_STRUCTURES_SCHEMA (AP218)	No
blower.stp	STRUCTURAL_ANALYSIS_DESIGN (AP209-like)	No
fullroom_aim.stp	PLANT_SPATIAL_CONFIGURATION (AP221)	No
ap224_997423743.stp	FEATURE_BASED_PROCESS_PLANNING (AP224)	No

Known Limitations

• Complex STEP files may cause crashes or rendering issues
• Large models may experience performance problems
• Some STEP file features may not be fully supported

Dependencies

• Rust (latest nightly)
• wasm-bindgen
• wgpu (WebGPU implementation)
• truck-* crates for geometry processing
• and some more ...

TODO

• Unit tests for the pure logic (math, caches, parsing, mesh metrics).
• Add support for STEP file features that are not currently supported.
• Clean up:
  • a lot of clone calls, most probably adding to perf issues.
  • some callbacks are not needed and/or triggered too often.
  • Alternative to Yew: less convoluted and more performant ?

Screenshots