CADScope

A browser-based 3D Viewer for CAD Assemblies, built with Three.js. Converts STEP files to Draco-compressed GLB with per-part colors and displays them in an interactive viewer with a scene hierarchy and preset camera views.

Viewing

1. Place a GLB file (preferrably draco compressed) in models/ (the viewer loads the path set in index.html)
2. Serve the project root: python -m http.server 8000
3. Open http://localhost:8000/index.html

Controls

• Left-drag — Orbit
• Middle/right-drag — Pan
• Scroll — Zoom
• View buttons (top-right) — Preset angles + zoom
• Scene hierarchy (left sidebar) — Expand/collapse nodes, toggle visibility
• Color pickers (left sidebar) — Change per-category part colors in real-time (when a color set file exists)

Converting STEP to GLB

Prerequisites:

• Python 3 (for STEP color extraction; stdlib only)
• Blender 5.0+ at /Applications/Blender.app
• FreeCAD 1.0+ at /Applications/FreeCAD.app --> you'll need to modify this to run on Linux or Windows; YMMV.

./model_converter/convert.sh models/input.step models/output.glb

# Without Draco compression
./model_converter/convert.sh --no-draco models/input.step models/output.glb

Pipeline

STEP → extract colors (Python) → FreeCAD (geometry + hierarchy) → Blender (apply colors + Draco) → GLB

Per-part colors are parsed directly from the STEP text (ISO 10303-21) since FreeCAD's headless mode can't access them. Colors are passed to Blender via a JSON sidecar and applied as Principled BSDF materials. Color extraction is non-fatal — if it fails, the pipeline still produces a valid GLB without colors.

You can inspect a STEP file's materials standalone:

python3 model_converter/extract_step_colors.py input.step /tmp/colors.json

Converter scripts

File	Role
convert.sh	Orchestrates the three-stage pipeline
extract_step_colors.py	Parses STEP text for color-to-part mappings (Python 3, no dependencies)
step_to_glb.py	FreeCAD script: STEP import, tessellation, uncompressed GLB export
blender_export.py	Blender script: GLB import, name cleaning, color application, Draco export
dump_parts.py	Extracts node names from a GLB into a .colors.json template

Color Sets

Color sets let you visualize different color schemes on 3D-printed assemblies by grouping parts into named categories (e.g. "Main", "Accent", "Extrusions"). A color picker appears in the sidebar for each category defined in the color set file.

Quick Setup

To scaffold a .colors.json from an existing GLB, use dump_parts.py:

python3 model_converter/dump_parts.py model.glb              # writes model.colors.json next to the GLB
python3 model_converter/dump_parts.py model.glb -o out.json  # explicit output path

This extracts all node names from the GLB and writes a template with empty categories plus two reference lists (_groups and _parts). Move names into category parts arrays, then delete the _ keys.

Models without a .colors.json file simply won't show the color pickers — no errors.

Manual Setup

Create a JSON file next to the GLB, named {model}.colors.json:

{
  "categories": {
    "Main": {
      "color": "#FF6600",
      "parts": ["PartNameA", "PartNameB"]
    },
    "Accent": {
      "color": "#00AAFF",
      "parts": ["PartNameC", "PartNameD"]
    }
  }
}

Add as many categories as you need — each one gets its own color picker in the sidebar. If a part matches multiple categories, the first one in file order wins.

For example, models/Positron_v3.2.2.glb looks for models/Positron_v3.2.2.colors.json.

Part names should match what you see in the sidebar hierarchy. The viewer uses the same name-cleaning logic as the conversion pipeline (strips path prefixes, .step suffixes, (mesh)/(group) suffixes) and will also try matching with trailing numeric suffixes (-1, -2, etc.) stripped, then fall back to the parent node name.

Future Possibilities...

??? ask! pull request!

Credits

The general look and feel was shamelessly copied, with love, from the VERY GOOD A4T Configurator for the A4T from Armchair Heavy Industries.