What causes procedural rivers that cross themselves or run uphill?

Tracing a river by following a fixed direction or by connecting random points ignores the terrain height, so the path can climb slopes and loop back over itself.

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 Procedural Rivers That Cross Themselves or Run Uphill

Quick answer: Trace rivers by steepest descent down the height field from a source, carving the channel as you go, and stop when you reach water or a local minimum you then fill into a lake.

Rivers that flow uphill or knot over themselves break immersion instantly. Driving the path with the actual height field keeps water moving downhill and forward.

How to fix it

1. Follow steepest descent

From each river cell, step to the lowest-height neighbor. This guarantees the river only ever flows downhill and never climbs a slope.

2. Resolve local minima into lakes

When a river reaches a pit with no lower neighbor, flood the basin to its lowest overflow point and continue the river from there, so the water never stalls or backtracks.

3. Mark visited cells to prevent crossings

Tag each cell the river occupies. If descent would re-enter a tagged cell, you have found a loop; terminate the river or merge it into the existing channel rather than crossing.

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.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.