fascat 0.4.0

convert CAD data into realtime-ready OpenUSD, glTF, OBJ, STL, and FBX assets

Fascat is a Python library and CLI for converting CAD data into RT3D assets.

flowchart TD
    A["STEP / IGES / BREP CAD"] --> B["Imported assembly"]
    B --> C["Tessellated meshes"]
    C --> D["Repaired meshes"]
    D --> E["Staged materials & UVs"]
    E --> F["Optimized LODs"]
    F --> G["OpenUSD / glTF / OBJ / STL / FBX"]

Installation

pip / pipx

pipx install fascat
# or
pip install fascat

Quick Start

# Show help
fascat --help
fascat help convert

# Print version
fascat version

# Inspect a CAD 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
fascat convert motor.step motor.glb --profile mixed-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 CAD assembly before conversion
fascat convert input.step [output.usdc]	Convert STEP, IGES, or BREP 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

asset = fc.read_step("motor.step")          # or read_iges(...) / read_brep(...)

asset = (
    asset.tessellate(sag=0.1, angle=15.0)
    .repair(tolerance=0.05)
    .stage(materials="cad", uv0="box")
    .optimize(target_triangles=500_000)
    .lods([0.5, 0.25, 0.1])
)

asset.write_usd("motor.usdc")
asset.write_gltf("motor.glb")

Keyword arguments mirror each operation's *Options dataclass; pass a prebuilt options object instead when you prefer (asset.repair(fc.RepairOptions(tolerance=0.05))).

Docs

Full documentation at pavelsimo.github.io/fascat.

License

MIT