“We will create the scene shown in the following image, there are 15 particles and three obstacles of various dimension. The locator on the right of the image is the target, the particles follows this target. The particles interact with each other and with the object in the scene, the interaction with the object simulates the obstacle avoidance and prevent the collision.”
http://www.3dtotal.com/team/Tutorials/simple_crowd/crowd_01.php