Wednesday, October 1, 2008

new improved VatLife posted

A fresh new version can be found at Spore it ain't, but I think the scientific underpinnings are better. ;)

So what are all these shapes and lines about?

First off, VatLife is a platform that separates the "environment" that creatures inhabit (which includes their physical form) from their "controllers", which contains logic for how each creature interacts with its environment. The thinking here is that any a-life can use any controller in any environment, and thus could migrate from one environment to another.

Because the environments and controllers are separate from VatLife and are loaded dynamically, what you're seeing isn't VatLife itself, but VatLife running a simulated environment with simulated controllers. The reason this is exciting to me is that someone out there could write a better evolvable controller, upload it, and it would just work in this environment (or any VatLife environment).

Enough preamble. The way this particular environment works is that each a-life has the physical form of a polygon, and will gain energy when "sunlight" (the vertical yellow lines) hits a face. Note that polygons can shade other polygons. Every a-life also loses energy each turn. The energy is shown by the polygon's color. Brighter colors mean higher energy, gray means low energy.

The simulation starts by generating twenty a-lifes using randomly generated genomes and randomly selected controllers. I've supplied two different controllers, neither of which are particularly good. The green polygons use one controller and the red polygons use another. The VatLife produces a polygon for an a-life by interpreting its genome. Complex polygons are allowed, but since they shade themselves, they're quickly selected against.

Periodically, the lowest-energy 50% are killed, and the top 50% are reproduced (with random mutations) to maintain a constant population. When this happens, you'll see a new "Generation #x" appear in the message box. I also give the existing a-life a good shake, so the new ones don't just settle on top of the old ones and shade them out.

So, what do the controllers get to do? Same as any VatLife controller - it can read and write pin values. In fact, I basically reused the controllers I'd used in the VatLife demo from two month ago. The environment handles pin I/O this way:

1) For an a-life, there are as many pins as there are polygon faces, with no child pins.

2) Each pin returns a value from 0 to 1 based on the amount of sunlight that polygon face is receiving.

3) Writing a value to a pin applies force to the polygon in the opposite direction that the face is pointing.

In other words, if a polygon has 4 faces, and it's rotated so that face #2 is on the bottom, reading pin #2 will return 0 (no sunlight) and writing to pin #2 will propel the a-life upwards.

If it's not obvious by now, that's what those magenta lines are about - they indicate the force that was applied from writing to a pin. If you see a line going on and off, that means the controller is using logic to control its propulsion.

Incidentally, the physics here isn't quite accurate on many levels. The force is applied to the center of the mass, not the center of the face as is shown. It's also a reactionless jet, which I'm very excited to have invented. ;) There's no fluid dynamics in play, although the top area above the blue background is a high gravity zone, which gives it some properties of being "above the water line".

Unfortunately, there's no data persistence - the simulation starts when you bring up the page and ends when you close it. With data persistence, you could have multiple environment in the central repository. Different users could sign in and simulate an environment for a number of turns, and evolved a-lifes could migrate from one to the other.

Unfortunately, all of that will have to wait, as I'm needing to turn my focus away from my hobby - and I'm curious to see if other people see value in this platform before investing more time in it.

I'll try to make the source code and some basic documentation available soon. Gerald de Jong has graciously offered to give it a code review, which is like having Leonardo da Vinci for your first year art teacher, so I will be polishing it first. This will be entirely open source.

Feedback, comments, questions are appreciated.