What causes physics substepping tanking frame rate with many bodies?

Substepping multiplies the per-frame solver work by the substep count, so with a large body count the physics step time balloons and the frame rate collapses.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix Physics Substepping Tanking Frame Rate With Many Bodies

Quick answer: Cap the maximum substeps, reduce solver iterations per substep, sleep or cull distant bodies, and only substep the fast objects that actually need it.

After turning on substepping to fix tunneling, your frame rate halved during busy scenes. Each substep re-runs the whole solver, so cost scales with substeps times bodies. Bounding substeps and trimming the active set restores performance.

How to fix it

1. Cap the substep count

Set a hard maximum on substeps (e.g. 2-4) so a frame spike cannot trigger many substeps and multiply solver cost into a death spiral.

2. Cut active bodies

Let distant or settled bodies sleep, disable physics on off-screen objects, and reduce the count of simultaneously simulated bodies so each substep is cheaper.

3. Substep selectively

Apply continuous detection or higher substep accuracy only to fast projectiles that need it, leaving slow bulk objects on a single step to keep total cost down.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.