Why does my convex MeshCollider lose detail?

PhysX caps convex hulls at 255 vertices. A high-poly mesh gets simplified to that limit before becoming a collider. For non-convex shapes, decompose with V-HACD and add multiple convex MeshColliders, or use primitive Box/Sphere/Capsule composites.

Volumetric Hierarchical Approximate Convex Decomposition. An algorithm that breaks a concave mesh into overlapping convex pieces. Each piece becomes a convex collider; together they approximate the concave shape with reasonable count.

Should I just use non-convex MeshCollider?

Non-convex MeshColliders work for static geometry only — they cannot collide with other non-convex MeshColliders. For dynamic Rigidbodies, you need convex. Decompose.

Fix: Unity MeshCollider Convex Hull Too Coarse

Quick answer: PhysX convex hulls cap at 255 vertices. For complex shapes, decompose into multiple convex pieces (V-HACD or Mesh Baker plugin) and add a MeshCollider per piece. For dynamic Rigidbodies, this is the only correct approach — non-convex Mesh-vs-Mesh isn’t supported.

Detailed kart mesh used as a Rigidbody collider. Convex MeshCollider produces a wrap that loses the wheel arches and rolls oddly. The simplification is the 255-vertex cap; multiple convex pieces are the answer.

The Symptom

Convex MeshCollider on a complex mesh produces a coarse hull visibly different from the source. Physics interactions feel wrong — objects can’t fit into negative spaces, balance is off.

The Fix

Decompose with V-HACD. Use the Asset Store package “Convex Decomposition” or run V-HACD offline (Blender plugin, command-line tool) and import the pieces.

Result: the original mesh becomes a hierarchy of child meshes, each approximating a convex region. Add a MeshCollider with Convex = true to each child.

Vehicle (root)
  — VisualMesh (MeshFilter + MeshRenderer)
  — Collision (Empty)
       — Hull_001 (MeshCollider Convex)
       — Hull_002 (MeshCollider Convex)
       — Hull_003 (MeshCollider Convex)
       ...

Multiple convex hulls collide with everything, including dynamic-vs-dynamic.

Primitive Composite

For simpler shapes, hand-build with Box/Sphere/Capsule colliders. A car can be one big Box plus four Capsules for wheel wells. Cheaper than mesh colliders and very controllable.

Performance

Each convex hull is a separate collision object. 10 hulls cost roughly 10x of one. Aim for 4–12 hulls per object for vehicles or large props; 1–3 for smaller items.

Verifying

Show physics colliders in Scene view. The combined collider hull should match the visible mesh outline. Drop the object on a complex surface; behavior should match expectations.

“Decompose. Compose. Multiple convex pieces are the rigid-body-friendly path.”

Related Issues

For Rigidbody sleep, see Rigidbody sleep. For tilemap collider edges, see tilemap collider.

Decompose. Multi-hull. Physics behaves.