Reports

Research notes, experiment summaries, and supporting media.

• Incremental potential contact in Newton Warp-native IPC design plus an experimental Newton cloth/plane implementation, with nested CUDA graph capture, stability testing, performance plots, and video.
• SDF grinding in Newton Short example of hydroelastic SDF-SDF contact, geometric material removal, and ViewerGL mesh updates.
• SuperDex vs Newton: two opposite bets on contact Meta's Project SuperDex shipped on 24 August 2026 with no paper and no benchmarks, so this reads its source, installs its wheels and measures it against Newton on matched scenes. SuperDex Physics turns out to be a CPU variational-implicit engine — Backward Euler/BDF/DIRK, Newton–Raphson with PSD projection, smoothed-penalty contact with IPC friction, SDF narrow phase with no GJK — and the shipped wheels cannot use a GPU: CUDA_CG throws at runtime. On a box pile it beats Newton's GPU XPBD by 31× at one body and loses by 8.4× at 216, crossing over at 48; Newton then adds a batch axis and reaches 679k env-steps/s on a seventh of a Blackwell. Resting penetration is invariant from 1 ms to 200 ms steps but is a pure function of load ÷ stiffness, and threading peaks at four workers then goes 2.7× backwards. Also situates SuperDex, MuJoCo, VBD/AVBD and Kamino as four different answers to what a contact is, plus two Newton crashes surfaced along the way.
• FeatherPGS grasp stability: what breaks, what to set, what to fix A Franka arm grasps and shakes a cube, and a two-pad coupon strips the same problem down to one contact. FeatherPGS has no gravity compensation, so a position-controlled arm sags 4.65° and never reaches its target pose; the contact-row budget defaults to ten contacts against a scene that needs seventy, and overflow is silent. Fix both and the grasp holds to 0.82 mm, or 0.32 mm with more iterations, with no contact tuning at all — and the coupon still holds at a 16.7 ms time step. Also covers a velocity pass that turns speculative contacts into walls, a squeeze a hard contact model cannot express, and an execution default that blocks CUDA graph capture. Interactive plots and ViewerGL rollouts.
• XPBD fluids in Newton vs. the OmniSurg PBF solver Head-to-head benchmark of Newton's position-based fluids against a faster external PBF implementation, both driven by one harness in one process against the same Model: Newton runs 8–12× slower, and the cause is that its density kernels re-query the hash grid on every solver iteration instead of reading a neighbor list materialized once per substep — 20× the marginal cost per iteration, and 91% of the frame in two kernels. Scaling, ablation and per-kernel breakdowns, a dam-break filmstrip showing the two flows agree, and a ranked list of fixes.
• Why a grasped cube creeps out of a two-finger gripper Root-cause investigation of grasp drift in Newton 1.4.0 + MuJoCo Warp 3.10: a Franka shake test loses 6.4 mm per 11.5 s and drops the cube outright at 10 cm amplitude. Friction, contact source, contact refresh rate, solver iterations and tolerance are all ruled out by measurement; the cause is contact compliance rectified by cyclic load, on finger pads still carrying the 2500 N/m import default because geom_priority discards everything authored on the object. Stiffening the pads gives a consistent ~20× reduction at identical simulation cost.
• manosim in Newton: replaying human grasps from HUG The unmodified manosim MANO hand MJCF driven by real 10 Hz HUG-Bench MANO trajectories against metric-scale scanned objects: an MJCF importer fix for slide+ball floating bases, headless ViewerGL montage and whole-scene replays, 60/60 stable rollouts with 2.2 mm wrist tracking, and the root cause of a ball-joint drive instability that MuJoCo hides by honouring dampratio and Newton does not.
• Tight-Fit Assembly in Newton: Solvers & Tunnelling Bring-up and solver investigation for gear-on-shaft and DisplayPort cable insertion on a Flexiv Rizon 4s: combined worktree, Kit-free headless env, ViewerGL video rollouts, a new VBD solver manager plus VBD/Kamino presets — and an isolated three-gear study showing the shipped meshes drive the train to 0.1% slip under XPBD at 100 Hz, while the training preset's MuJoCo contact path convex-hulls the teeth and shafts away for 100% slip.
• Newton Gym: graph-captured RL environments for Newton FlashSAC vs PPO on cartpole, ant, and G1 locomotion; single-CUDA-graph step pipeline, 22M env-steps/s scaling, multi-GPU scaffolding.
• SolverMACFluid: two-way coupled incompressible fluid for Newton Staggered MAC-grid incompressible fluid solver coupled to MuJoCo through Newton's experimental proxy framework: solver-native buoyancy/drag/torque wrenches with roundoff-level action–reaction, bit-exact coupling-iteration restarts, CUDA-graph stepping, validation tables, and settling-sphere, motor-paddle, and articulated-swimmer demos — including 30 s+ large-tank rollouts (out-and-back marathon, three-swimmer race, nine-link eel), a realistic 50 cm robot at 1200 kg/m³ in true-viscosity water on 2.7M cells, and a wake-fidelity study showing the new clamped MacCormack advection preserving 3× the wake energy of semi-Lagrangian.
• Neural connections inside Warp kernels NeuralSim-style patchbay prototype for Warp: named wires in kernels re-wired from Python with @wp.func nonlinearities and tiny inlined MLPs — modular synth demo (audio included), a trained hybrid simulation, and a puck-on-table demo that recovers a spatial friction heatmap through a position-driven neural connection.
• HRDexDB dexterous-grasp replay in Newton 120 real xArm6 + Allegro V5 / Inspire F1 picking episodes replayed fully dynamically with SolverMuJoCo: PD joint targets only, passive objects colliding as watertight CoACD decompositions, ground-truth overlay videos, per-hand CMA-ES calibration with winner's-curse revalidation, and median object-tracking error of 4–8 cm across 35 objects.
• Flying Knots in Newton Mid-air overhand knot tied by an xArm7 replaying the paper's digitized throw with SolverVBD cable joints: trajectory digitization, IK-driven arm, knot-topology metrics, tuned 17/20 kinematic success, and a fully dynamic MuJoCo-coupled variant that ties the knot 12/12.
• DiscoGrad-style program smoothing in Warp Gaussian smoothing helpers for branch-heavy Warp objectives, with triangle intersection gradients, 2D collision optimization, variance plots, and CPU benchmark tables.
• SHAC with MuJoCo Warp Latest MJWarp PR #1535 retest: full-horizon Ant and Humanoid gaits now pass 3×1024-lane audits, guarded analytic-SHAC checks, and exact-trajectory ViewerGL video gates—with root causes, checkpoints, and raw results.
• ViewerGL Transparency Rendering Cross-system screenshot and frame-time comparison of sorted back-to-front blending and weighted order-independent transparency for transparent meshes and cloth.
• Newton XPBD Fluid Support XPBD density projection, cohesion, viscosity, two-way rigid coupling, anisotropic surface reconstruction, the public fluid API, stability coverage, and RTX 4090 benchmarks—with six ten-second simulations spanning an Archimedes screw pump, dam break, multiple fluids, waves, buoyant bodies, and robot cup transfer.
• Newton assets without ArticulationRootAPI Design options and evidence for jointed USD mechanisms that have no articulation root, including JointView and importer-inferred articulation strategies.
• Featherstone Origin-Offset Numerical stability investigation and benchmarks for floating-base Featherstone articulations driven far from the world origin.
• Newton Determinism Scenario results, diagnostics, and accompanying videos.
• Deterministic mesh inertia Latest Warp PR #1355 rerun for Newton mesh inertia: V2 original atomic lowering is bit-exact and much faster after the multi-component reduction update; V3 tile_sum remains fastest.
• Newton Mimic Joints Design alternatives, parameterization tradeoffs, benchmark results, and schema evidence.
• Newton Cutting Simulation Literature overview and concrete Newton/Warp implementation paths for real-time soft-object cutting.
• Newton ModelBuilder Performance ModelBuilder.finalize() and add_builder() timing and memory benchmarks for replicated USD RL workloads and targeted optimization variants.
• Real2Sim Parameter Estimation Literature groups, Newton toolbox design, and a Franka/Warp prototype for estimating robot and object physical parameters from real data.