What causes frame drops from too many overlapping realtime lights?

Each realtime light that touches a pixel adds a full lighting evaluation, so a cluster of overlapping shadow-casting lights multiplies per-pixel cost and tanks the frame rate.

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 Frame Drops from Too Many Overlapping Realtime Lights

Quick answer: Bake or set non-essential lights to Mixed/Baked, reduce light range so fewer lights overlap each pixel, limit shadow casters, and rely on a tiled/clustered renderer.

Realtime lighting cost scales with how many lights hit each pixel. A room packed with overlapping realtime shadow-casting lights re-shades every pixel many times. Baking most of them and trimming overlap restores performance.

How to fix it

1. Bake the lights that do not move

Set static decorative lights to Baked or Mixed so they cost nothing per frame. Only lights that must respond to dynamic objects need to stay realtime.

2. Shrink light range and overlap

Tighten each light's range so fewer lights cover any given pixel. Overlap is the multiplier; reducing it cuts per-pixel evaluations directly.

3. Limit realtime shadow casters

Shadows are the expensive part; let only a few key lights cast realtime shadows and disable shadows on fill lights, which players rarely notice.

4. Confirm a clustered/forward+ path

Use a clustered or Forward+ renderer so light culling is per-cluster; legacy forward rendering re-renders geometry per light and amplifies the cost.

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.