Fix: Unity NavMesh Preview Not Visible in Scene View

Here is how to fix Unity NavMesh preview not visible in Scene view. You baked a NavMesh. Click Bake. Button says “baked successfully.” Scene view shows no blue overlay. You know the bake exists because your agents navigate. But you cannot visually confirm mesh coverage, which makes it impossible to debug narrow corridors or dropped sections.

The Symptom

Scene view does not show the blue NavMesh overlay. Agents at runtime pathfind correctly, confirming bake exists. NavMeshAgent SamplePosition returns valid hits. But visual confirmation is missing.

What Causes This

Navigation window closed. The NavMesh overlay only draws while the Navigation window is open (or while a NavMeshSurface is selected in newer AI Navigation package). Closing the window hides the preview.

Show NavMesh gizmo disabled. Scene view > Gizmos dropdown. Look for “NavMesh” or “AI” category. Checkbox must be on. Even with the Navigation window open, the gizmo toggle overrides.

Wrong Agent Type selected. If you baked for “Humanoid” but the Agent Type dropdown in Navigation window shows “Large Enemy,” you see the Large Enemy’s bake (possibly empty), not Humanoid.

Alpha set too low in Preferences. The NavMesh color has an alpha channel. If low, the overlay is effectively invisible on busy scenes. Reset to defaults.

Bake data missing. If you never actually baked, agents may pathfind on some leftover bake from a previous scene. Or the bake data is in the scene but corrupted. Re-bake to ensure.

The Fix

Step 1: Open the Navigation window. Window > AI > Navigation. Switch to the Object or Bake tab. The blue overlay should appear in Scene view on walkable geometry. If not, proceed to the next step.

For Unity 2022.2+ with AI Navigation package, select a NavMeshSurface component; the bake preview appears when the component is selected.

Step 2: Enable NavMesh gizmo. Scene view > Gizmos dropdown (top-right). Scroll to find NavMesh or Navigation. Check all related categories.

Many projects have custom Scene view filters that hide navigation gizmos. If the checkbox was disabled in a previous session, it stays disabled.

Step 3: Pick the correct Agent Type. In Navigation window > Bake tab, check Agent Type dropdown. Cycle through each to see their bakes. If only one exists, it should always be selected.

If your project has multiple agent types (for different sized units), each has its own bake. Inspect each to verify.

Step 4: Reset NavMesh color. Preferences (Edit > Preferences) > Colors > Navmesh. Reset to default (bright cyan). Check alpha is high. If the mesh was hidden via color tweaks, this fixes it.

Force Rebake

If nothing else works, force a fresh bake:

1. Navigation window > Bake tab
2. Clear (removes all bake data)
3. Bake

The Clear button removes the current NavMesh asset. Bake re-runs from scratch. After baking, the overlay should definitely appear.

AI Navigation Package Version

Unity’s legacy NavMesh system (built-in) and the AI Navigation package (com.unity.ai.navigation) differ. The legacy system uses the Navigation window; the package uses NavMeshSurface components. Which one you use affects where to look for the preview.

For the package: select the NavMeshSurface GameObject. In the Inspector, the surface shows a preview of its bake, including agent radius. The Scene view also shows the mesh when this component is selected.

Understanding the issue

Navigation meshes are precomputed. Changes to geometry invalidate the precomputation; runtime regenerates may take long enough that the player notices. Plan invalidation timing carefully.

The specific bug described above is the kind that surfaces during integration rather than unit testing. It depends on a combination of factors: the asset configuration, the runtime state, the platform's specific behavior. In isolation, each piece looks correct; in combination, the bug emerges. This is why thorough integration testing - playing the actual game in realistic conditions - catches things that automated tests miss.

Why this happens

This bug class disproportionately affects late-stage development. The work to surface it is interactive testing in realistic conditions, which only really happens after the gameplay is in place and assets are populated. Catching it early requires deliberate testing of conditions that look unimportant.

At the engine level, the behavior comes from a deliberate design decision in Unity. The engine team chose a particular trade-off - usually performance versus convenience, or generality versus specificity - and that trade-off has consequences when you push against it. Understanding the trade-off is what turns 'this bug is mysterious' into 'this bug is the expected consequence of this design'.

Verifying the fix

Verifying this fix in isolation is straightforward: reproduce the bug, apply the change, confirm the bug no longer reproduces. The harder verification is regression - did this fix introduce a new bug elsewhere? Run your standard regression suite, plus any tests that exercise the same code path with different inputs.

Reproducibility is the prerequisite for verification. If you can't reliably reproduce the bug pre-fix, you can't reliably verify it post-fix. Spend time getting a clean reproduction before you write any fix code. The fix is fast once you understand the reproduction; the reproduction is the slow part.

Variations to watch for

There's almost always a less obvious case where the same problem applies. The reported case is the one a player hit; the related cases hide because they're rarer or affect fewer players. After fixing the reported case, search the codebase for the pattern - one fix often unlocks several.

Adjacent bugs often share a root cause. After fixing the case you've found, spend an hour searching the codebase for similar patterns. What's the same call with different arguments? The same data flow with a different entity type? The same lifecycle issue in a sibling system? Each match is a candidate for the same fix, or a related fix that prevents future bugs of the same class.

In production

For shipping titles with a long support window, watch for this issue resurfacing after dependency updates. Engine upgrades, driver updates, OS releases - each one can resurface a bug class you thought you'd fixed because the underlying behavior changed slightly. Regression tests catch the obvious ones; player reports catch the rest.

When triaging a similar issue in production, prioritize gathering data over hypothesizing causes. A player report describes a symptom; what you need is a build SHA, a session timestamp, and ideally a screen recording or session replay. With those, the bug becomes tractable. Without them, you're guessing at hypothetical reproductions that may not match what the player actually hit.

Performance considerations

If this issue manifests under high load (many actors, many particles, many network connections), profile the post-fix code path with realistic counts. The original cost was a bug; the new cost is real work, and real work has a budget.

Diagnostic approach

Before applying any fix, gather enough context to be confident you're addressing the actual cause and not a similar-looking symptom. The cheapest diagnostic step is reproducing the bug deterministically - if you can't get the same failure twice in a row, your fix attempts will be hard to evaluate. Lock down the reproduction first.

For Unity-specific diagnostics, the editor's profiler is the canonical starting point. Capture a representative frame with the symptom present; compare against a frame without the symptom; the diff often points directly at the cause. If the symptom is non-deterministic, capture multiple frames and look for the pattern - the cause is usually a state transition or a specific input value rather than a continuous effect.

Tooling and ecosystem

Modern engine versions ship better tooling for this kind of issue than older versions. If you're on an older release, the diagnostic step may take significantly longer because the tools you'd want don't exist yet. Sometimes the right answer is upgrading rather than fighting through limited tooling.

Within Unity, the relevant diagnostic surfaces include the standard frame debugger, memory profiler, and engine-specific debug overlays. Each one shows a different facet of what's happening. The frame debugger reveals draw call ordering and state transitions; the memory profiler shows allocation patterns; the debug overlay reveals per-system state. Bugs that resist one tool usually surrender to another - the trick is knowing which tool to reach for first.

Edge cases and pitfalls

Edge cases for this class of issue often involve specific timing: the first frame after a state change, the last frame before a transition, frames where multiple subsystems update simultaneously. Reproducing these reliably is part of what makes the bug class hard to test.

When writing a regression test for this fix, focus on the boundary conditions that surfaced the original bug. Tests that exercise the happy path catch obvious regressions; tests that exercise the boundary catch the subtler regressions that look like new bugs but are really the original returning. The latter are the tests that earn their keep over the long life of the project.

Team communication

When this bug class affects multiple teams (often the case for cross-system issues), early communication prevents duplicate work. The team that owns the symptom may not own the cause. A 15-minute conversation at the start of triage often saves hours of independent investigation.

If this fix touches a system several engineers work in, a short writeup in the team's engineering channel helps. Not a full design doc - a paragraph explaining what was wrong, what's fixed, and what to watch for. Future engineers encountering similar symptoms will search for the fix; making it findable is a small investment that pays back later.

“The NavMesh is there even if you cannot see it. The preview is a tool; the mesh works regardless. But verify visually when things go wrong.”

Related Issues

For agent stuck issues, see NavMeshAgent Stuck on Edge. For bake failures, NavMesh Building Fails on High-Poly Mesh.

Navigation window open + Scene view gizmo on + default color. Three switches show the mesh.