fascat 0.1.0

convert CAD STEP data into realtime-ready OpenUSD and glTF assets

🐱 fascat

Fascat is a Python library and CLI for converting CAD STEP data into realtime-ready OpenUSD and glTF assets.

The V1 pipeline is intentionally narrow:

STEP CAD -> imported assembly -> tessellated meshes -> repaired meshes -> staged materials and UVs -> optimized LODs -> OpenUSD/glTF

Installation

Homebrew (macOS / Linux)

brew tap pavelsimo/homebrew-tap
brew install fascat

pip / pipx

pipx install fascat
# or
pip install fascat

Quick Start

# Show help
fascat --help
fascat help convert

# Print version
fascat version

# Inspect a STEP assembly
fascat inspect motor.step
fascat --json inspect motor.step

# Convert STEP to binary OpenUSD
fascat convert motor.step
fascat convert motor.step motor.usdc --profile realtime-desktop

# Convert STEP to binary glTF for VR/runtime engines
fascat convert motor.step motor.glb --profile virtual-reality

# Tune tessellation, UVs, optimization, and LODs
fascat convert motor.step motor.usdc \
  --sag 0.1 \
  --angle 15 \
  --max-edge-length 25 \
  --target-triangles 500000 \
  --materials display \
  --uv1 box \
  --lods 0.5,0.25,0.1

# Preview a conversion without writing files
fascat convert motor.step motor.usdc --dry-run

# Emit a debuggable ASCII USD and report
fascat convert motor.step motor.usda --debug --report report.json

# Validate generated output
fascat validate motor.usdc
fascat validate motor.glb

Commands

Command	Description
fascat inspect input.step	Inspect a STEP assembly before conversion
fascat convert input.step [output.usdc]	Convert STEP CAD into OpenUSD or glTF
fascat validate output.usdc	Validate generated USD or glTF output
fascat help [command]	Show top-level or command-specific help
fascat version	Print version and exit

Fascat follows standard CLI stream conventions: primary output and JSON go to stdout, while errors and per-stage conversion progress go to stderr. Conversion validates the generated asset before reporting success. File arguments accept - for stdin/stdout where meaningful.

Python API

import fascat as fc

fc.convert(
    "pump.step",
    "pump.usdc",
    tessellation=fc.Tessellation(sag=0.1, angle=15, max_edge_length=25),
    stage=fc.StageOptions(materials="cad", uv0="box", uv1="unwrap"),
    optimize=fc.OptimizeOptions(target_triangles=1_000_000, preserve_instances=True),
    lods=fc.LODOptions((0.5, 0.25, 0.1)),
)

asset = fc.read_step("pump.step").tessellate().repair().stage().optimize()
asset.write_gltf("pump.glb")

Docs

Full documentation at pavelsimo.github.io/fascat.

License

MIT