Archive for November, 2011

Subversion RIP

It’s a great shame to hear that Introversion Software, a London based indie game developer, have decided to put on hold Subversion, a game of great interest to anyone involved in PCG.  The company has decided to take some of the technology they built for the project and focus on another game called Prison Architect, which should be good news as they’ll undoubtedly be making sensible commercial decisions.

There is a full interview here, and has many topics worth considering for an indie developer, or anyone involved in PCG.

  1. Worlds and Levels created by PCG techniques are, more often than not, really boring to play.  This is a biggie – you can make a computer generate the most beautiful landscapes, plants and water features, but this stuff has a tendency to repeat itself to infinity, which is no fun at all.  Even the makers (well publishers) of Elite limited the number of galaxies from the possible 256 million to only 8, on the basis that the player would lose all interest in the ridiculous scale.  Successful PCG games like Minecraft ensure that the players can design their own unique architecture over the world of mathematics, this generates interest for other players.
  2. Making something more realistic does not make it more fun.  Everyone knows that the KISS (keep it simple stupid) mantra is the most important in UI, UX, product, game, or pretty much any other design, however it’s very difficult for an artist to follow this simple rule, even more so when there is an elegance to making the environment fully integrated to the point otherwise designed laws naturally emerge.  I’ve been following Introversion for a long time and I can see the quandary they would have been in: as proponents of PCG as a necessity to make up for lack of human level designers, it became more tempting to generate everything well past the position of utility.
  3. It’s a highly complex (possible unsolvable) problem to simulate architecture that would otherwsie been created by a human (or even animal) builder.  The most immediate uses of PCG may be as a tool to generate ideas that human (or crowd of) designers then curates by selecting and modifying into something useful.

The direction of my research is in creating software agents that can assist human designers (or crowds of them) generate more interesting levels, either by evaluating the raw creations of PCG, or perhaps by simulating human behavior in shaping their environment, or even learning how designers create content and replicating these fuzzy techniques.  Introversion software have been pioneering these techniques for many years, and so I wish them the best in commercial success with Prison Architect so they have more time to play with creating virtual worlds.

Plant Growth

Generating plants and fauna has been one of the primary successes of computer graphics over the last few decades, most people would be surprised at how often the plants in a film or advert are virtual copies of the real thing.

A simple way to create plants is using Lindenmayer Systems, which take a starting string and over a number of steps re-write the original string based upon simple rules.

So for example we could start with the character A and every time we iterate we replace the letter A with AB, and if we find a B we replace it with letter A. This gives us a series that looks like:


and so on.  Visually we could change the characters to directions for an image drawer (things like turn left, turn right, draw forwards) and instantly we’ve produced some nice little snowflakes.

We can generate all sorts of interesting shapes by making tiny additions to those initial rules, such as adding the ability to jump spaces without drawing, changing colour, all in all a very simple way to make some familiar looking patterns.

Where things get more dynamic is if we allow the algorithms to maintain a stack of visited matrices, which means to branch, a bit like trees.

Move into the realm of 3D and we begin to get some very lifelike trees.  Of course trees are not made up of identical sticks from root to branch, so we need to add in a little stochastic sampling (randomness in the growth) as well as the idea that the tree will grow seasonally, and a trunk will grow differently to a branch, a leaf or a flower, however all of this can be managed with some imagination.

To get an idea of how far this has come, check out the virtual arboretum managed by SpeedTree, a company which specializes in dreaming up virtual fauna.  To get some more details of how the magic happens, I’d recommend The Algorithmic Beauty of Plants by Przemyslaw Prusinkiewicz and Aristid Lindenmayer.