What causes using lerp instead of slerp on rotations in Godot?

Linear interpolation of quaternion components or raw angles does not move at constant angular velocity and can take the long way around, so a turn that should be smooth visibly eases and may reverse.

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 Using lerp Instead of slerp on Rotations in Godot

Q: How do you fix using lerp instead of slerp on rotations in Godot?

Use Quaternion.slerp (or Basis.slerp) for orientation, not lerp. Slerp interpolates along the shortest arc on the rotation sphere at a uniform rate.

Quick answer: Use Quaternion.slerp (or Basis.slerp) for orientation, not lerp. Slerp interpolates along the shortest arc on the rotation sphere at a uniform rate.

If a rotating object accelerates in the middle of its turn or briefly spins the wrong way, you are probably lerping rotations. Slerp fixes both the speed and the direction. Here is the change.

How to fix it

1. Switch to slerp for quaternions

Replace a.lerp(b, t) with a.slerp(b, t) on Quaternion values. Slerp keeps the magnitude unit-length and moves at constant angular speed.

2. Use angle wrapping for 2D

For a single 2D rotation, interpolate with lerp_angle(from, to, t) which takes the shortest path across the -PI/PI boundary instead of plain lerp.

3. Normalize before slerping

Slerp assumes unit quaternions. If you built one from raw math, call normalized() first so the interpolation arc is well defined.

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 Godot 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.

A crash you can name from its stack trace is a crash you can usually fix in minutes.