FEMS – Finite Element Material Simulation

HAVE you ever wondered what it looks like to suspend a cube of jelly from one corner, let it swing a bit, then let it go and watch it land and bounce, and try the same thing with different amounts of gelatine?

Quite possibly not, but here is the chance to try it anyway. Download and extract the zip-file below, and run ‘fems.exe’. With any luck, you should see a lightsource-shaded cube drop down from the top of the screen, with one corner stretching out as it is attached to some imaginary fixed point, and eventually start to swing back and forth, much like it is shown in the picture on the right.

To release the cube, press Space. It will either bounce on the ground or collapse depending on how strong the jelly is, and how high it was dropped from. There is an invisible ledge to the left of the cube: if you let it go at the right time, it will either fall straight down or land and topple over the edge - in both cases it will continue to fall into a bottomless pit.

The effect of the demo can be changed by editing the lines of ‘world.txt’. The important lines are the ones labelled `k' and `damping' - making them higher will produce stiffer jelly, lowering them makes the jelly somewhat runnier (and less bouncy). The program ignores whatever is written after the number on a line, but don't add or remove any extra lines. If the `k' and damping are set too high, the jelly has a tendancy to explode (I don't know where the extra energy comes from ... perhaps from the carbohydrate). To remedy this, increase the `time resolution', though this will slow the demo down.

The still pictures here don't really do the demo justice, so I recommend you download it and run it, preferably on a fast machine with a 3D graphics card. My P200 with Voodoo1 will show it at 60fps.