What causes a blotchy or smeared result from the lightmap denoiser?

The denoiser removes noise by blurring across texels, so when the underlying bake is heavily undersampled it has too little signal and turns grain into low-frequency blotches or smears fine shadows away.

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 a Blotchy or Smeared Result from the Lightmap Denoiser

Quick answer: Raise the bake sample count so the denoiser has real signal, increase lightmap resolution for fine detail, and pick the appied denoiser (Optix/OpenImageDenoise) that suits the scene.

A denoiser cleans grain, but if the bake is starved of samples it smears the result into blotches and erases small shadows. Feeding it a better-sampled, higher-resolution bake produces clean output.

How to fix it

1. Increase samples before denoising

Raise direct and indirect sample counts so the pre-denoise bake is reasonably converged. The denoiser sharpens a noisy-but-real signal; it cannot invent detail from near-zero samples.

2. Raise lightmap resolution for detail

Smeared small shadows usually mean texels are too large for the detail; increase texel density so fine occlusion survives the denoise pass.

3. Choose the right denoiser

Try the alternative denoiser (OpenImageDenoise vs Optix, or the engine's built-in) since they trade off blotchiness against sharpness differently on flat versus detailed surfaces.

4. Rebake and compare with denoise off

Bake once with denoising disabled to see the true noise level; if it is already clean, lower the denoise strength so it stops introducing blotches.

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.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.