def report_collision_vs_world(cls, px, py, dx, dy):
p = DP(cls.pos)
o = DP(cls.oldpos)
# calc velocity
vx = p.x - o.x
vy = p.y - o.y
# find component of velocity parallel to collision normal
dp = vx * dx + vy * dy
# project velocity onto collision normal
# nx, ny is normal velocity
nx = dp * dx
ny = dp * dy
# px, py is tangent velocity
tx = vx - nx
ty = vy - ny
# we only want to apply collision response forces
# if the object is travelling into, and not out of, the collision
if dp < 0:
# f = cls.settings.get('FRICTION')
f = 0.05
fx = tx * f
fy = ty * f
# self bounce constant should be else:where, i.e inside the object/tile/etc..
# b = 1 + cls.settings.get('BOUNCE')
b = 1 + 0.3
bx = nx * b
by = ny * b
else:
# moving out of collision, do not apply forces
bx = by = fx = fy = 0
# project object out of collision
p.x = p.x + px
p.y = p.y + py
# apply bounce+friction impulses which alter velocity
o.x = o.x + px + bx + fx
o.y = o.y + py + by + fy
cls.pos = DP(p)
cls.oldpos = DP(o)
def integrate_verlet(cls):
d = 1.0
g = 0.2
p, o = DP(cls.pos), DP(cls.oldpos)
ox, oy = o.x, o.y
# integrate
p.x = p.x + (d * p.x) - (d * ox)
p.y = p.y + (d * p.y) - (d * oy) + g
cls.oldpos = DP(cls.pos)
cls.pos = p
