How to Fix Grenade Trajectory Preview Not Matching the Thrown Arc

Players line up a perfect bank shot using the preview, then the grenade lands feet away. The preview and the throw use different numbers. Sharing one set of physics parameters fixes the mismatch. Here is how.

How to fix it

1. Share one set of throw parameters

Compute the launch velocity, spawn position, and gravity once and feed both the preview and the spawned grenade. If the real throw uses physics gravity, sample Physics.gravity, not a hand-typed constant.

2. Simulate the arc analytically

Plot the preview points with p(t) = p0 + v0*t + 0.5*g*t*t at small time steps, then raycast each segment to find the first impact and stop there, so the line ends exactly where the grenade will hit.

3. Match the bounce model

If the grenade bounces, reflect the preview velocity off the impact normal with the same restitution the physics material uses, so the predicted bounce path tracks the thrown one.

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 Unity 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.