Spinning top

Basic contacts

A spinning chuck winds up a top and lets it go on its tip.

Play0.00 s

¼×½×1×2×

Loop

The steel preset (the default), recordedon an NVIDIA RTX PRO 6000 Blackwell.

Run it

cd examples
# the default preset (steel), then the others
uv run shelf play spinning_top
# change solver settings live
uv run shelf tune spinning_top

Source: examples/shelf/01_basic_contacts/spinning_top/ · ported from steel-webgpu assets/scenes/spinning_top (hero_montage export) @ ad03e49

Presets

Preset	Solver	Status	Checked
steeldefault	steel	works	2026-11-10, newton f6fc82a8b, NVIDIA RTX PRO 6000 Blackwell Server Edition

Solvers with no row are untested on this example. The full settings are inpresets.toml.

Code

example.py

examples/shelf/01_basic_contacts/spinning_top/example.py

# SPDX-FileCopyrightText: Copyright (c) 2026 Skild AI and the Steel contributors
# SPDX-License-Identifier: Apache-2.0
# Direct source: steel-webgpu; see presets.toml and THIRD_PARTY.md.
# Modified for Steel Shelf: preset-driven execution and shared runner integration.

###########################################################################
# Example Spinning top
#
# A motorised chuck grips the top's stem, spins it up and releases it; the top keeps spinning upright on its tip.
#
# Rebuilt from steel-webgpu's exported scene (assets/scenes/spinning_top: scene.json
# and scene.bin, copied next to this file); see common/exported_scene.py. The
# visual meshes draw when a steel-webgpu checkout sits next to the shelf.
#
# Command: python -m shelf run spinning_top
#
###########################################################################

import newton.examples
from common.exported_scene import ExportedSceneExample


class Example(ExportedSceneExample):
    file = __file__


if __name__ == "__main__":
    parser = Example.create_parser()
    viewer, args = newton.examples.init(parser)
    newton.examples.run(Example(viewer, args), args)

example.py on GitHub

presets.toml

examples/shelf/01_basic_contacts/spinning_top/presets.toml

example = "spinning_top"
source = "steel-webgpu assets/scenes/spinning_top (hero_montage export) @ ad03e49"
default = "steel"

[check]
# Arguments `python -m shelf check` passes in test mode.
args = []

[gallery]
short = "A spinning chuck winds up a top and lets it go on its tip."
title = "Spinning top"
frame = 240

[xpbd]
status = "untested"

[vbd]
status = "untested"

[mujoco]
status = "untested"

[featherstone]
status = "untested"

[semi_implicit]
status = "untested"

[feather_pgs]
status = "untested"

[steel]
status = "works"
# 4 substeps x 12 iterations, friction anchors on (3.84 ms/frame on an RTX PRO 6000, the port's 4 x 16 5.10): the
# chuck spins the top to ~20 rad/s, releases it within 1 deg of vertical, and it spins on its tip with its axis
# 3.3-4.7 deg off vertical at 9 s (3 runs), as 16 x 48 runs (3.5-3.9 deg); spin decays to ~15 rad/s in every configuration.
# 4 x 8 (3.16 ms) drifts to 4.4-5.0 deg, 3 x 12 to 4.3-7.7. With the gripper's finger mimic (cfeff10) anchors off
# is unsafe: the opening fingers knocked the top 5-14 deg in 5 of 7 runs at 4 x 12 and 6 x 12, and it fell.
# Joint limits on (the fingers stop at [0, 0.04] m). The joints' velocity limits are 1e6 (none), so those rows are
# off, and the row capacities fit the scene (peaks: 18 dense, 33 propagation rows).
sim = { fps = 60, substeps = 4 }
solver = { solve_mode = "matrix_free", iterations = 12, articulated_contact_response = "propagation_colored", enable_joint_limits = true, enable_joint_velocity_limits = false, free_body_constraint_max = 64, articulation_constraint_max = 64, propagation_constraint_max = 128 }
checked = "2026-11-10, newton f6fc82a8b, NVIDIA RTX PRO 6000 Blackwell Server Edition"

[kamino]
status = "untested"

[implicit_mpm]
status = "untested"

[style3d]
status = "untested"

presets.toml on GitHub

← Sliding blocksAll examplesPinch grip →