How to Fix Z-Fighting on Coplanar Decals and Surface Overlays

A poster, blood splat, or floor marking flickers against the wall or ground it lies on as the camera moves. Two coplanar surfaces are fighting for the same depth. Here is how to separate them.

How to fix it

1. Add a depth bias

Use a polygon offset or depth bias on the decal material so it consistently resolves in front of the base surface. This shifts its depth just enough to win without a visible gap.

2. Nudge it toward the camera

Push the overlay geometry a small distance along the surface normal toward the viewer. A tiny offset removes the coplanar tie that causes the per-pixel flicker.

3. Use a dedicated decal pass

Render decals in a pass that does not depth-test against the surface they sit on (or uses a stencil mask), so their visibility is decided by the pass order rather than by an exact depth comparison.

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.