@ferret/physics-friction

friction function

function friction(): Capability

On a kernel without contact hooks (Havok) the same dials reach the solver another way: each body's surface is its material's friction times the scale where the body is, and rolling resistance (which Havok lacks) is a torque μr·N·r against the roll, with N the normal force the body's contacts carried in the last step. Anisotropy and pivot friction need the hooks.

packages/physics-friction/src/index.ts:21

FRICTION_DEFAULTS const

const FRICTION_DEFAULTS: { scale: number; rollingScale: number; pivot: number | undefined; anisotropy: { axis: Vec3; across: number; } | undefined; }

friction by scope. The kernel already applies Coulomb static and kinetic friction, rolling resistance and (optionally) pivot friction from the materials of the two surfaces; this adds what a game dials per scope, so a patch of ice can be a zone as well as a material:

  scale         multiplies static and kinetic friction                           (1)
  rollingScale  multiplies the rolling resistance                                (1)
  pivot         pivot (spinning) friction coefficient, overriding the material   (the material's)
  anisotropy    { axis: [x,y,z], across }: across the axis the coefficient is `across` times the one along it
                (an ice skate: across ≈ 20; a rail or a ski)

packages/physics-friction/src/index.ts:14