sprite.py 文件源码

def elasticCircles(mass1, mass2):
    "Set final velocities for an elastic collision between two circles"

    # Calculate the normal vector at contact point
    x1, y1 = mass1.rect.center
    x2, y2 = mass2.rect.center
    nx = x2 - x1
    ny = y2 - y1
    r = hypot(nx, ny)
    if r >= mass1.radius + mass2.radius or r == 0:
        return # No contact!
    nx /= r
    ny /= r

    # Calculate initial momenta
    m1 = mass1.mass
    m2 = mass2.mass
    v1x, v1y = mass1.vel
    v2x, v2y = mass2.vel
    p1x = m1 * v1x
    p1y = m1 * v1y
    p2x = m2 * v2x
    p2y = m2 * v2y

    # Calculate impulse and final velocities
    impulse = 2 * (m2 * (p1x * nx + p1y * ny) - m1 * (p2x * nx + p2y * ny)) / (m1 + m2)
    if impulse > 0:
        mass1.vel = (p1x - impulse * nx) / m1, (p1y - impulse * ny) / m1
        mass2.vel = (p2x + impulse * nx) / m2, (p2y + impulse * ny) / m2
        return True