Common Physics Pitfalls

1. Scale Issues

Problem: Non-uniform scaling can cause physics behavior to be unpredictable.

Solution: Use mesh.scaling.isEqual(BABYLON.Vector3.One()) to check for uniform scaling. If non-uniform scaling is needed, create a properly sized collision mesh as a child of the visual mesh.

// Bad practice: Non-uniform scaling with physics

box.scaling = new BABYLON.Vector3(1, 2, 1);

box.physicsImpostor = new BABYLON.PhysicsImpostor(...);



// Good practice: Use a separate collision mesh

const visualMesh = BABYLON.MeshBuilder.CreateBox("visual", {width: 1, height: 2, depth: 1}, scene);

const collisionMesh = BABYLON.MeshBuilder.CreateBox("collision", {size: 1}, scene);

collisionMesh.scaling = new BABYLON.Vector3(1, 2, 1);

collisionMesh.visibility = 0;  // Invisible collision mesh

collisionMesh.physicsImpostor = new BABYLON.PhysicsImpostor(...);

2. Mesh Parenting Issues

Problem: Physics impostors may not work correctly with parented meshes.

Solution: Apply physics to the root mesh or use compound bodies for complex hierarchies.

3. Tunneling (Objects Passing Through Each Other)

Problem: Fast-moving objects may pass through thin objects due to discrete time stepping.

Solution: Use continuous collision detection or increase the number of substeps.

// Enable CCD (Continuous Collision Detection) for fast objects

// Note: Implementation depends on physics engine

sphere.physicsImpostor.physicsBody.setCcdMotionThreshold(1);

sphere.physicsImpostor.physicsBody.setCcdSweptSphereRadius(0.2);

4. Performance Issues with Many Objects

Problem: Too many physics objects can severely impact performance.

Solution: Use instancing, compound bodies, and LOD for physics.

5. Stability Issues with Constraints

Problem: Joints and constraints can become unstable, causing objects to jitter or explode.

Solution: Use appropriate constraint limits, damping, and ensure proper initialization.

// Add damping to stabilize physics objects

box.physicsImpostor.setLinearDamping(0.1);

box.physicsImpostor.setAngularDamping(0.1);

6. Collision Filtering Issues

Problem: Objects collide with things they shouldn't, or don't collide with things they should.

Solution: Use collision groups and masks to control what collides with what.

// Set collision groups (implementation varies by physics engine)

playerMesh.physicsImpostor.physicsBody.collisionFilterGroup = 2;  // Player group

playerMesh.physicsImpostor.physicsBody.collisionFilterMask = 1;   // Collide only with environment



enemyMesh.physicsImpostor.physicsBody.collisionFilterGroup = 4;   // Enemy group

enemyMesh.physicsImpostor.physicsBody.collisionFilterMask = 1;    // Collide only with environment

7. Initialization Order Issues

Problem: Physics behaviors depend on proper initialization order.

Solution: Always ensure physics engine is initialized before creating impostors, and impostors are created before joints/constraints.

8. Garbage Collection Pauses

Problem: Creating and destroying many physics objects can trigger garbage collection, causing stutters.

Solution: Reuse physics objects using object pooling, and dispose of unused objects properly.

// Proper disposal of physics objects

function cleanupPhysicsObject(mesh) {

    if (mesh.physicsImpostor) {

        mesh.physicsImpostor.dispose();

        mesh.physicsImpostor = null;

    }

    mesh.dispose();

}