How to Fix a Curve-Driven Blend Weight Stuck at Zero in Unreal

Your blend or morph target driven by an anim curve stays at zero no matter what plays. The curve is not being evaluated into the AnimBP because it lacks the right type flag. Exposing it makes GetCurveValue return real values.

How to fix it

1. Mark the curve as exposed

In the animation's curve settings ensure the curve's type flags include the right category (e.g. Attribute/Material/Morph) so it is evaluated and reachable from the AnimBP.

2. Read it with GetCurveValue

In the AnimBP use Get Curve Value with the exact curve name (names are case-sensitive) to drive the blend weight; a typo returns the default zero.

3. Enable curve metadata on the skeleton

Confirm the skeleton's curve metadata includes the curve and is not stripped on import, otherwise the curve exists in the clip but is not evaluated at runtime.

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 Unreal Engine 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.