DynaMo is a software library providing classes that take care of the calculation of the motions of objects under the influence of force, torque, and impulse. It can also compute forces for you through the mechanism of constraints. These allow you to easily connect geometries to each other in various ways. A constraint only has to be specified once, and the library will continually enforce it from that moment on by applying the required reaction forces. Over a dozen constraints available, including several types of hinges and a constraint for collision response calculations.
