Why do players fall through the floor in my game?

Most commonly tunneling: a fast-moving object moves so far in one physics step that it passes entirely through a thin collider, never registering the collision (it was above the floor one step, below it the next). It can also be gaps or holes in the collision geometry, or colliders that are too thin or missing. Tunneling correlates with speed; geometry gaps correlate with specific locations.

How do I stop fast-moving objects from tunneling through colliders?

Enable continuous collision detection (CCD) for fast-moving objects like the player and projectiles. CCD checks the swept path between physics steps, so a fast object can't pass through a thin collider undetected, the standard tunneling fix. Also avoid too-thin colliders (make floors and walls thick enough not to be tunneled) and consider smaller physics steps for very fast objects.

How do I recover players who fall through the floor?

Add out-of-bounds detection as a safety net: detect when the player has fallen below the level or into the void, and recover them by teleporting back to a safe spot or checkpoint. This catches any fall-through that slips past your collision fixes, so even an unforeseen one doesn't strand or kill the player. Combine it with fixing the collision causes (continuous collision detection, closing geometry gaps) for a robust solution.

How to Fix Collision Bugs That Let Players Fall Through the Floor

Quick answer: Players falling through the floor is a collision-detection failure, most commonly tunneling (a fast-moving object passes through a thin collider between physics steps because it moved further than the collider's thickness in one step), plus gaps or holes in collision geometry and thin/missing colliders. Fix it with continuous collision detection for fast objects, thicker colliders, and closing collision gaps, and add out-of-bounds detection that recovers the player as a safety net.

Falling through the floor (or walls) is a classic, immersion-breaking, and often progress-threatening bug. It's a collision problem, the physics failed to keep the player on the right side of a surface, and the most common cause (tunneling) is a well-understood physics phenomenon with a standard fix. Combined with closing geometry gaps and a recovery safety net, it's very solvable.

Why Players Fall Through Surfaces

Collision should prevent the player from passing through surfaces, but it can fail. Tunneling, the most common cause: a fast-moving object moves so far in a single physics step that it passes entirely through a thin collider, in one step it was above the floor, the next it's below, never registering the collision because it 'teleported' through between steps. This is worse with fast movement and thin colliders. Gaps/holes in collision, the collision geometry has gaps (seams between colliders, missing colliders, holes) the player can fall through, even if the visual geometry looks solid. And thin/missing colliders, colliders too thin (easily tunneled) or missing entirely on some surfaces.

So falling through is either the physics missing the collision (tunneling, against thin colliders, especially at speed) or the collision not being there to begin with (gaps, holes, missing colliders). Tunneling correlates with speed; gaps correlate with specific locations.

How to Diagnose It

Determine which cause. Does it happen with fast movement (falling fast, high speed)? That points at tunneling. Does it happen at specific spots (the same place, a seam, an edge)? That points at a gap/hole in collision there. Reproduce the fall-through and note the speed and location. Check your colliders, are they thin (tunnel-prone)? Are there gaps in the collision geometry at the fall-through spots? Is continuous collision detection enabled for fast objects?

Player reports pinpoint where it happens ('I fell through the floor at X'), which is invaluable for finding collision gaps. Bugnet captures reports with context, so fall-through reports and their locations surface, helping you find the specific gaps and the conditions (speed) behind tunneling. The location and speed pattern distinguishes tunneling (speed-related, anywhere thin) from geometry gaps (location-specific).

How to Fix It

Fix per cause and add a safety net. For tunneling, enable continuous collision detection (CCD) for fast-moving objects (the player, projectiles), CCD checks the path swept between physics steps so fast objects can't pass through thin colliders, this is the standard tunneling fix. Also avoid too-thin colliders (make floors/walls thick enough not to be tunneled) and consider smaller physics steps for very fast objects. For gaps/holes, close the gaps in collision geometry, fix seams between colliders, add missing colliders, ensure surfaces that look solid actually have solid collision. For thin/missing colliders, thicken or add them where needed.

Crucially, add an out-of-bounds recovery safety net, detect when the player has fallen out of bounds (below the level, into the void) and recover them (teleport back to a safe spot/checkpoint), so even a fall-through that slips past your fixes doesn't strand or kill the player. After fixing, verify players can't fall through at the problem spots or speeds, and that the recovery catches any that do. Continuous collision detection plus solid geometry plus out-of-bounds recovery is the robust combination that keeps players on the right side of the floor.

Falling through the floor is usually tunneling (fast objects through thin colliders) or gaps in collision. Use continuous collision detection, thicken colliders, close gaps, and add out-of-bounds recovery.