How to Fix Flat or Double Shadows from Subtractive Mixed Lighting in Unity

Subtractive lighting is the cheapest mixed mode but it fakes dynamic shadows with one flat color, so they look crushed and double up over baked shadows. Adjusting the shadow color or moving to Shadowmask fixes it.

How to fix it

1. Set the realtime shadow color

In Lighting > Mixed Lighting, adjust Realtime Shadow Color to roughly match your scene's ambient. The default often crushes dynamic shadows to black or makes them clash with baked ones.

2. Switch to Shadowmask for correct overlap

Change Mixed Lighting Mode to Shadowmask. It stores static shadow occlusion in a texture so dynamic and baked shadows combine correctly instead of doubling.

3. Use Baked Indirect for full realtime shadows

If you want fully realtime direct shadows with baked bounce, choose Baked Indirect mode. It costs more but avoids the flat subtractive shadow entirely.

4. Rebake after changing modes

Each mixed mode bakes different data, so re-run the lighting bake after switching and verify dynamic objects no longer show flat or doubled shadows.

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.