Class: Pongo::CollisionResolver

Inherits:
Object
  • Object
show all
Defined in:
lib/pongo/collision_resolver.rb

Class Method Summary collapse

Class Method Details

.resolve(pa, pb, normal, depth) ⇒ Object 



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# File 'lib/pongo/collision_resolver.rb', line 5

def self.resolve(pa, pb, normal, depth)
  mtd = normal * depth
  te = pa.elasticity + pb.elasticity
  sum_inv_mass = pa.inv_mass + pb.inv_mass

  # the total friction in a collision is combined but clamped to [0,1]
  tf = MathUtil.clamp(1 - (pa.friction + pb.friction), 0, 1)

  # get the collision components, vn and vt
  ca = pa.components(normal)
  cb = pb.components(normal)

  # calculate the coefficient of restitution as the normal component
  vn_a = (cb.vn * ((te + 1) * pa.inv_mass) + 
    (ca.vn * (pb.inv_mass - te * pa.inv_mass))) / sum_inv_mass
  vn_b = (ca.vn * ((te + 1) * pb.inv_mass) + 
    (cb.vn * (pa.inv_mass - te * pb.inv_mass))) / sum_inv_mass

  # apply friction to the tangental component
  ca.vt.mult!(tf)
  cb.vt.mult!(tf)

  # scale the mtd by the ratio of the masses. heavier particles move less 
  mtd_a = mtd * ( pa.inv_mass / sum_inv_mass)
  mtd_b = mtd * (-pb.inv_mass / sum_inv_mass)

  # add the tangental component to the normal component for the new velocity 
  vn_a.plus!(ca.vt)
  vn_b.plus!(cb.vt)

  pa.resolve_collision(mtd_a, vn_a, normal, depth, -1, pb)
  pb.resolve_collision(mtd_b, vn_b, normal, depth,  1, pa)
end