Fix: Godot CharacterBody3D Wall Slide Jitter

Here is how to fix Godot CharacterBody3D wall slide jitter. Your player pushes into a wall and instead of sliding smoothly along it, the character vibrates or stutters. Sometimes it bounces between two nearby walls in a corner. Sometimes the camera follower shows microshake while the body looks stable. Godot’s built-in move_and_slide is well-tuned for simple cases but has three knobs that interact in non-obvious ways when walls are close or angled.

The Symptom

Pressing into a wall with diagonal input makes the character shiver along the contact. Moving into a concave corner produces a visible bounce. Sloped walls alternate between “treated as floor” and “treated as wall” from frame to frame, snapping the player’s position.

Variant: is_on_wall() toggles true/false every other frame during a slide, breaking animation state machines keyed to wall contact.

What Causes This

max_slides too low. Each call to move_and_slide runs a fixed number of collision resolution iterations (max_slides, default 4). In a corner where the resolved direction bounces off multiple surfaces, 4 is not enough to converge. The solver leaves residual motion, which the next frame tries to resolve — producing oscillation.

wall_min_slide_angle misclassification. Surfaces between vertical and the min-slide angle are treated as walls. Below it, they are treated as floors or ceilings. A sloped surface near the threshold flips classification based on minor normal fluctuation.

slide_on_ceiling interactions. With slide_on_ceiling = true, a character grazing a ceiling slides horizontally. With it off, ceiling contact stops vertical motion. Near overhangs the classification can flip between wall and ceiling.

Velocity recomputed after collision. A common bug: after move_and_slide, user code zeroes or overwrites velocity based on input. Next frame pushes the same velocity back into the wall, producing a step pattern.

Physics ticks vs render ticks. Camera following in _process interpolates between physics states. Without interpolation on the body, the camera shows physics-frame jitter amplified.

The Fix

Step 1: Tune slide parameters.

extends CharacterBody3D

func _ready():
    max_slides = 6
    wall_min_slide_angle = deg_to_rad(15)
    slide_on_ceiling = false
    floor_max_angle = deg_to_rad(45)

max_slides = 6 gives the solver enough passes to converge in sharp corners without measurable cost. Values above 8 rarely help and add compute.

wall_min_slide_angle around 15 degrees (0.26 rad) means anything within 15 degrees of vertical acts as a wall. Below that, it becomes a floor. Pick a value that matches your level geometry — steep ramps should be “floors,” near-vertical cliffs should be “walls.”

Step 2: Preserve velocity after move_and_slide. Do not overwrite velocity from input every frame. Accumulate input, then call move_and_slide, and let it return the actual resolved velocity:

func _physics_process(delta):
    var input_dir = Input.get_vector("left", "right", "fwd", "back")
    var target = Vector3(input_dir.x, 0, input_dir.y) * SPEED

    velocity.x = move_toward(velocity.x, target.x, ACCEL * delta)
    velocity.z = move_toward(velocity.z, target.z, ACCEL * delta)
    velocity.y -= GRAVITY * delta

    move_and_slide()

After move_and_slide, velocity reflects post-collision motion. Let it ride into the next frame rather than recomputing from raw input.

Step 3: Disable slide_on_ceiling for platformers. Jumping into an overhang with slide-on-ceiling enabled makes the character skim along the ceiling, then drop. With it disabled, the character’s upward velocity clears on contact, which feels natural for Mario-style games.

Step 4: Raise solver_iterations for precision. For physics-heavy scenes, tune the Project Settings > Physics > 3D > Solver Iterations value. Default 16 is fine for most games; increase to 24 if you still see residual jitter in tight spaces.

Debug with get_slide_collision

To inspect what the solver actually touched:

for i in get_slide_collision_count():
    var c = get_slide_collision(i)
    print("hit ", c.get_collider(), " normal ", c.get_normal())

If the same body appears multiple times per frame with flipping normals, the solver is bouncing. Raise max_slides or simplify the collision geometry.

Corner Case: Two Walls at Acute Angle

In a 45-degree corner, the naive solve picks one wall, slides, hits the other, slides back, repeat. The fix is projected input: detect wall normals and flatten input into the wedge direction rather than letting the solver fight:

if is_on_wall():
    var n = get_wall_normal()
    velocity = velocity.slide(n)
move_and_slide()

This pre-projects velocity parallel to the dominant wall, reducing solver work and eliminating the bounce pattern.

Understanding the issue

This bug class falls into a pattern that's worth understanding beyond the specific case. In Godot Engine, the underlying behavior is shaped by how the engine layers its abstractions - the public API you call, the runtime systems that respond, and the platform-specific implementations underneath. A bug at any layer can produce symptoms that look like they originate at a different layer. Triaging effectively means recognizing which layer the symptom belongs to, even when the gameplay code is what's visible.

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

The triage path for this kind of bug is long. The symptom appears in gameplay, but the cause is in a different system. The reporter describes the gameplay effect; the engineer has to translate that into a hypothesis about the underlying cause. Misdirection is common.

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

For shipping games, the safest verification is a staged rollout. Apply the fix to 1% of players for 24 hours; watch the affected metric; expand if green. Skipping the staged rollout means the verification is the entire player base, which is too high a stakes for most fixes.

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

Live games surface this bug class at scale. What's a rare edge case in development becomes a daily occurrence once you have a few thousand concurrent players. The class isn't 'this player has a unique setup'; it's 'one in N thousand sessions will trigger this exact combination'.

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

The diagnostic tools available depend on your engine and platform. Use the engine's native profilers and debug overlays before reaching for external tools. The native tools have context that external tools lack - they know which subsystem owns the code, which assets are loaded, and what state the engine is in.

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

Third-party plugins often provide better diagnostics for their own behavior than the engine does. If the affected code is in a plugin, check the plugin's documentation for debug modes, verbose logging, or inspector tools - these can save hours of investigation when they exist.

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

Platform-specific edge cases are worth enumerating explicitly. iOS handles backgrounding differently than Android; Windows handles focus changes differently than macOS. A fix that works on the development platform may not work on every target. Test on each shipping platform deliberately.

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

Document the fix and its rationale in the commit message or attached engineering doc. Future engineers will encounter related issues; the rationale tells them whether your fix is reusable or specific to the case at hand. Without rationale, the fix gets reverted or copied incorrectly.

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.

“Four slides is not enough for a corner. Six is usually plenty.”

Related Issues

For related physics tuning, see Area2D Not Detecting StaticBody2D. For camera jitter that compounds with physics jitter, Viewport Mouse Position Offset shares root-cause territory.

max_slides 6, slide_on_ceiling off, preserve velocity. Smooth slides, no shake.