10 natural effects
For a more natural look, add the WANDER force. On each step calculate a random direction based on a noise function. This random vector adds to the direction the seed gets moved. For better balancing, also introduce two weighting factors to the interface, scaling our forces up or down. The result is vines growing with a lot more variation, but they now penetrate obstacles they meet. To avoid this, the third type of force comes in handy, the WALL direction.