How to Fix an Alpha-Clipped Shader Casting Solid Quad Shadows in Unity

Alpha cutout shaders discard transparent fragments in the main pass, but the lightweight shadow caster pass often skips texturing entirely. The result is a billboard tree with a blocky rectangular shadow. Here is how to fix it.

How to fix it

1. Clip inside the ShadowCaster pass

In a hand-written shader, sample the albedo's alpha in the shadow pass fragment and call clip(alpha - _Cutoff) so the shadow silhouette matches the visible one.

2. Enable Alpha Clipping on the material

For URP/HDRP Lit materials, turn on Alpha Clipping and set the threshold; the pipeline then applies the clip to the shadow caster automatically.

3. Check shadow map resolution

If the cutout edge is still chunky, raise shadow resolution or bias; aggressive clipping on a low-res shadow map produces aliased silhouettes regardless of the clip being correct.

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.