ammo-mmd-physics-hacks

Cloth explosions in Ammo.js MMD physics usually come from incorrect kinematic body synchronization. Replace direct setWorldTransform calls with MotionState-based updates so Bullet computes proper collision momentum, and add a velocity limiter that clamps linear velocity above 50 and angular velocity above 30.

Hair stretching during dragging happens when Mode 2 rigid bodies are downgraded to Mode 1, losing their anchor points. Restore proper Mode 2 kinematic sync using setCenterOfMassTransform with MotionState updates, and set activation state to 4 to prevent bodies from sleeping.

No, raising numIterations to high values like 100 destroys browser frame rates on the single-threaded main loop. The recommended approach is code-space constraints such as velocity clamping, differentiated collision margins, and local gravity transforms instead of brute-force solver iterations.

Ghost clipping occurs because bone-synced torso bodies use setWorldTransform, which teleports them each frame with no continuous motion state, giving Bullet no momentum feedback. Feeding transforms through getMotionState().setWorldTransform() lets the engine derive impact velocity and repel incoming cloth.

Creating new Ammo.btVector3 objects inside per-frame loops leaks WASM heap memory because JavaScript garbage collection cannot reach the underlying C++ allocations. Reuse a single persistent vector instance and update it with setValue() each frame instead.

Global downward gravity crushes clothing against the body when the character lies flat. Convert gravity to a local body-relative direction using the mesh quaternion, and bind the floor plane's rotation to the mesh so the ground follows the character's orientation.