how it works
simple bits
looking at the fluid, lifelike way these creatures walk and roll and slink across the screen you might think that there must be some very complicated stuff going on behind the scenes. well fear not, it's actually very simple. it only looks complicated because lots of simple bits are working together
when simple bits work together you can get emergent behaviour. that means that the system as a whole can be more complex and sophisticated than the simple bits that it's made out of
let's look at the bits
masses
masses are simple things that obey a simple law. masses accelerate when a force is applied to them
when a mass is moving it has kinetic energy. the environment absorbs some of this energy when the mass moves through the air or collides with surfaces. this loss of energy makes masses slow down
create a mass in openconstructor; you can pick it up by dragging it upward with your mouse. when you let go the force of gravity makes it accelerate back down to the ground
friction with the air and the ground slows the mass down and makes it come to a rest rather than bouncing forever
springs
springs connect masses. the spring applies forces to the masses when it is stretched or squashed. the spring force obeys a simple law, the force is in proportion to the distance that the spring is stretched or squashed
try creating a free mass and a fixed mass connected by a spring, then drag it around with your mouse and get a feel for how the force is in proportion to the amount that you stretch or squash the spring
muscles
muscles are exactly like springs with one simple difference. a spring has a fixed length at which it is at rest and does not apply forces to its masses. with a muscle this length isn't fixed, it changes over time, making the muscle push and pull (note, in real life muscles don't push, they only pull). a wave pattern is used to control the way these muscles expand and contract over time
create a muscle and watch it get bigger and smaller in time to the movement of the wave
working together
that's all the bits you need to make moving creatures. they're all pretty simple, but they're also pretty boring. it gets interesting when you put all those bits together
play with some of the ready made creatures or practice building your own and you'll be surprised by how many different lifelike moving creations you can make by getting all the simple bits to work together