DiSMech-Newton

Discrete elastic rods and midedge shells for NVIDIA Newton, inspired by Daviet (2023).

Examples

Cantilever	Overhand Knot	Plectoneme	Flagella Bundling
DER (top) and Newton's VBD (bottom) against Euler-Bernoulli. uv run examples/cantilever.py	A knot pulled tight with friction Audoly et al. (2007). uv run examples/overhand_knot.py	A twisted rod coils into a plectoneme Clauvelin et al. (2009). uv run examples/plectoneme.py	Flagella bundle in a viscous fluid Tong et al. (2022). uv run examples/flagella.py --flagella 10
Shell Cantilever	Shell Fold	Cloth Twist	Franka Pick and Place
Midedge shells beside Newton's VBD cloth against plate theory. uv run examples/shell_cantilever.py	A cloth strip folds onto itself with self-contact friction. uv run examples/shell_fold.py	A sheet wrung into a coiling rope by self-contact with friction. uv run examples/newton/cloth_twist.py	A MuJoCo Franka picks up a cable. uv run --extra mujoco examples/newton/franka_cable_ik_pick_place.py

Newton's own cable and cloth examples (pile, plectoneme, Y junction, hysteresis, cross slide table, Franka pick and place, hanging and draped cloth, ...) run on SolverDiSMech in examples/newton/. See examples/ for what each example adds.

Install

Requires Python 3.10+. Runs on an NVIDIA GPU with CUDA 13 (cuDSS through the gpu extra) or on the CPU (SciPy).

pip install "dismech-newton[gpu]"           # add `mujoco` for the coupled examples, `viewer` for the viewer

Usage

import newton
import numpy as np
from dismech_newton import SolverDiSMech

builder = newton.ModelBuilder()
points = np.linspace([0.0, 0.0, 1.0], [1.0, 0.0, 1.0], 21)  # a 1 m rod, 20 segments
bodies, _ = SolverDiSMech.add_rod(builder, rod=newton.Rod(points, radius=0.01), bend_stiffness=1.0e-2)
SolverDiSMech.fix_segment(builder, bodies[0])  # clamp the first segment
model = builder.finalize()
solver = SolverDiSMech(model)
state_0, state_1 = model.state(), model.state()
for _ in range(100):
    solver.step(state_0, state_1, None, None, 1.0e-2)  # finds its own contacts
    state_0, state_1 = state_1, state_0

Shells come from SolverDiSMech.add_cloth_mesh with Newton's add_cloth_mesh arguments.

Development

uv sync --extra gpu --extra mujoco --group dev
uv run pytest            # physical checks against theory and finite differences
uv run pytest -m slow    # the examples