Press on it
Drag the plate down. The dent is not an animation — it is the
finite-element solution for this foam, swept around the axis of the plate.
Let go and it comes back.
Twin Mattress
0.95 × 1.90 × 0.20 m · 16.10 kg · 45 kg/m³ foam
Indentation force
0110155220 N
Force0.0 N
In pounds0.0 lbf
Plate travel0.0 mm
Plate area323.0 cm²
Plate radius101.4 mm
Why not just use a formula
Elastic half-space—
This bonded layer—
Stiffer by1.65×
The closed-form answer is 65% low. Foam
in a real mattress sits on a solid base and cannot flow away under the
plate. That gap is the whole reason this is simulated.
Where the shape comes from. The plate press is axisymmetric, so the
problem reduces exactly to two dimensions — no approximation. We solve it with
4-node axisymmetric quadrilaterals and 2×2 Gauss quadrature, then sweep the
surface displacement around the axis. Because the material model is linear,
the field scales with travel, so every depth you drag through is the exact
solution rather than a blend between keyframes.
We stop at 25% and will not quote 65%. At 65% compression foam cells
buckle and densify. A linear model pushed that far would overstate the force
badly, so no IFD65 and no support factor are published. It would need a
hyperelastic model — Ogden or Hill. A missing number beats an unverified one.
What the shipped file does. MattressTwin_v1.usdz is a
rigid body with one exact convex collider — right mass, right size, right
shape. It does not squash at runtime. The figure here describes the
foam the asset represents, and it is reproducible with one command:
python3 harness/09_ifd_fem.py 0.20 7194 0.30
Computed result for a synthetic asset. Not a laboratory test and not a
certification. Foam properties are a declared specification, not a
measurement — there is no physical specimen. 3DS Bull is not a testing
laboratory and is not affiliated with, endorsed by, accredited by, or
certified by ASTM International, BSI, or ISO. The designation ASTM D3574 is
cited descriptively, to identify which analytical method was used.