brepax 0.3.0

Differentiable rasterizer for CAD Boolean operations — JAX-native B-Rep kernel with stratum-aware gradients.

BRepAX

JAX-native differentiable B-Rep kernel with NURBS support.

BRepAX loads STEP files into a JAX computation graph, enabling gradient-based optimization of CAD geometry through Boolean operations. It provides stratum-aware differentiation that handles topological transitions at Boolean boundaries, and supports both analytical primitives and freeform B-spline surfaces.

Installation

pip install brepax

Quick Start

import jax.numpy as jnp
import equinox as eqx
from brepax.io.step import read_step
from brepax.brep.csg_stump import reconstruct_csg_stump, stump_to_differentiable
from brepax.metrics import surface_area, thin_wall_volume

# Load STEP file and build differentiable representation
shape = read_step("part.step")
stump = reconstruct_csg_stump(shape)
diff = stump_to_differentiable(stump)

# Compute metrics
lo, hi = jnp.array([-1.0] * 3), jnp.array([41.0, 31.0, 21.0])
vol = diff.volume(resolution=32, lo=lo, hi=hi)
area = surface_area(diff.sdf, lo=lo, hi=hi, resolution=32)
thin = thin_wall_volume(diff.sdf, 2.0, lo=lo, hi=hi, resolution=32)

# Gradient of volume w.r.t. all design parameters
grad = eqx.filter_grad(lambda d: d.volume(resolution=16, lo=lo, hi=hi))(diff)

Features

Primitives

9 geometric types with differentiable SDF interface: Plane, Cylinder, Sphere, Cone, Torus, Box, FiniteCylinder, Disk, and BSplineSurface (rational NURBS with weights).

STEP Pipeline

• Read STEP files via OCCT (cadquery-ocp-novtk)
• Convert all face types to primitives (100% conversion on 4,080 faces across 28 test files)
• PMC-based CSG-Stump reconstruction (tested up to 664 faces)
• Differentiable volume, metrics, and gradients end-to-end

Differentiable Metrics

8 metrics, all differentiable via jax.grad:

Metric	Description
volume	Sigmoid indicator integral
surface_area	Sigmoid-derivative delta function
center_of_mass	Volume-weighted position average
moment_of_inertia	Inertia tensor with Richardson extrapolation
thin_wall_volume	Volume below wall thickness threshold
min_wall_thickness	Soft-argmax with sub-grid refinement
draft_angle_violation	Surface area with insufficient draft angle
undercut_volume	Surface-weighted undercut severity

Boolean Operations

Union, subtract, intersect with stratum-dispatched gradients. Analytical exact gradients for bounded primitive pairs in 3 of 4 topological configurations.

Documentation

Full documentation: lv416e.github.io/brepax

License

Apache License 2.0. See LICENSE for details.