Workaround: objects appearing to "fall asleep" / freeze midair

[ryichando]

Who this affects: Anyone whose simulation shows an object stalling or hanging in place when it shouldn't, for example a ball that stops dead in midair instead of continuing through or bouncing off a net or cloth.

The symptom

During simulation, a solid (e.g. a ball thrown at a net) stops moving and stays completely still in midair, as if the physics "fell asleep," even though nothing should be holding it there. See the video in #50 for an example.

Why it happens

This is a limitation of the solver engine rather than a bug. In these setups the system becomes hard to solve, and with the default settings the solver can't make enough progress, so the object stalls. It usually shows up when a light, fast solid interacts with a thin, stiff obstacle like a net.

The workaround

Try either of these parameter tweaks:

• Tighten the PCG tolerance. In Advanced Params -> PCG Tolerance, lower the value. A tighter tolerance makes each solve more accurate so the motion resolves correctly.

• Increase density. Raising the density (e.g. from 0.2 to 10.0) makes the system better conditioned and the object behaves as expected.

Either one resolved the stalling in #50; pick whichever fits your scene.

Ideally the add-on should warn about this, or the solver should auto-tune these parameters. Until then, if you see similar strange behavior, please try tweaking these settings first.