momentumExchange

taichi_glsl.lagrangian.momentumExchange(v1, v2, disp, m1=1, m2=1, gamma=1)

Exchange momentum (bounce) between two objects.

momentumExchange should be invocated when a bounce occurred. It takes the velocity of two objects before bounce, and returns the velocity of two objects after bounce.

This function is most useful in rigid-body simulation with collision. For example:

if distance(pos[i], pos[j]) < radius[i] + radius[j]:
    # Collision detected! Perform a momentum exchange:
    vel[i], vel[j] = momentumExchange(
        vel[i], vel[j], mass[i], mass[j], pos[i] - pos[j], 0.8)

Parameters

• v1 – (Vector) The velocity vector of the first object to bounce. Or, the velocity vector at the collision point in first object.

• v2 – (Vector) The velocity vector of the second object to bounce. Or, the velocity vector at the collision point in second object.

• disp – (Vector) The displacement vector from between two object. Or, the normal vector of collision surface. Specifically, for balls or circles, disp is pos1 - pos2.

• m1 – (scalar) The mass of the first object to bounce.

• m2 – (scalar) The mass of the second object to bounce.

• gamma – (scalar) The decrease factor of bounce, in range [0, 1], determines how much energy is conserved after the bounce process. If 1, then no energy is loss; if 0, then the collided objects will stops immediately.

Returns

(tuple of Vector) The return value is a tuple of velocity of two objects after bounce. Specifically the first element is for the velocity of first object (previously to be v1), and same to the second element.

Note

For usage example, check out this: https://github.com/taichi-dev/taichi_three/blob/master/examples/many_balls.py