Fix: Godot Light2D Shadow Not Cast From TileMap

Here is how to fix Godot 4 Light2Ds that illuminate the scene but cast no shadows from your TileMap walls. The light is real, the wall is solid, the player can’t walk through it — but the light shines straight through. Light2D uses a separate occluder system from collisions, and TileMap tiles need explicit occluder polygons.

The Symptom

A Light2D with shadow_enabled = true creates dynamic shadows from LightOccluder2D nodes you placed manually, but TileMap walls cast no shadow. The light passes through walls regardless of texture.

What Causes This

No Occlusion Layer in TileSet. The TileSet asset must have at least one Occlusion Layer added before tiles can have occluder polygons.

Polygons not drawn. Adding the layer enables drawing; you still need to actually draw a polygon on each wall tile.

Wrong layer mask. Light2D’s Range Layer Min/Max determines which occluder layers it sees. Mismatched layers means the light ignores those occluders.

shadow_enabled off. The Light2D’s shadow needs explicit enable.

The Fix

Step 1: Add an Occlusion Layer to the TileSet. Open the TileSet asset. In the right panel, find Occlusion Layers. Click the + to add one. Set its Light Mask to the value you want (default 1).

Step 2: Draw polygons on each wall tile. Select a wall tile in the TileSet editor. Switch to the Occlusion Layer tab. Draw a polygon matching the visible silhouette. Repeat for each wall variation.

Step 3: Enable shadows on Light2D.

extends PointLight2D

func _ready():
    shadow_enabled = true
    shadow_color = Color(0, 0, 0, 0.7)
    shadow_filter = Light2D.SHADOW_FILTER_PCF5
    range_layer_min = 0
    range_layer_max = 0
    range_z_min = -1024
    range_z_max = 1024

Step 4: Match shadow item cull mask. The Light2D’s Shadow Item Cull Mask must include the bit corresponding to the TileMap’s Light Mask. Defaults usually match, but custom configurations require alignment.

Step 5: Verify in Scene view. Move the Light2D around. Walls should cast shadows that follow the light source. If shadows still do not appear, double-check the Occlusion Layer was added before drawing polygons (drawing without a layer added does nothing).

Per-Tile Variations

Different tiles can use different occluder polygons. A diagonal wall tile gets a triangular polygon; a half-wall gets a smaller rectangle. Match each tile’s actual silhouette for accurate shadows.

Animated Tiles

Animated tiles can change their visible art per frame. The occluder polygon stays static. For doors that visually open, also call tile_set_cell with a non-occluder version when the door opens, or animate the alternative tile.

Understanding the issue

Tilemaps are dense data structures. A single tile change touches several other systems: rendering, collision, possibly navigation. Bugs at the intersection often look like 'I changed one tile, why did three other things break'.

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 Godot. 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

After applying the fix, the verification step has three parts: confirm the original repro is resolved, confirm no obvious regressions in adjacent functionality, and (for shipping titles) deploy to a small player cohort first and watch the crash and report rates. Each step catches something the others miss.

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

Related bug classes often share the same root cause. If you find yourself fixing this issue, look for cousins: similar symptoms in adjacent systems, the same data flow but a different value, or the same fix pattern in another module. The catalog of 'we've seen this before' becomes valuable institutional knowledge.

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

Diagnosing this class of bug benefits from a structured approach: confirm the symptom, isolate the variables, hypothesize the cause, and verify the hypothesis before writing fix code. Skipping the isolation step is the most common mistake; without it, fixes often address symptoms while the underlying cause continues to produce other variations.

For Godot-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 Godot, 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

Boundary conditions deserve specific testing attention. What happens when the input is zero, maximum, negative, or NaN? What happens at the start of a session vs hours in? What happens at the boundary between two systems handling the same data? These are where bugs hide and where regression tests are most valuable.

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.

“Light2D needs occluder polygons in the TileSet. Collisions do not double as occluders. Draw the silhouette per tile.”

Related Issues

For TileMap Y-sort, see TileMap Y-Sort. For collision shape disable, see CollisionShape Disabled.

Add Occlusion Layer. Draw polygons. shadow_enabled = true. Walls block light.