In this technical article
, originally published in Game Developer magazine, Neversoft co-founder Mick West explores making your own mini-languages for games by making Whimsy, a domain-specific language that creates art based on the abstract paintings of Parappa
creator Rodney Alan Greenblat.
Unlike general-purpose languages, a domain-specific language must support a large amount of functionality, such as variables, data structures, conditional expressions, looping constructs, and functions. DSLs can be classified as either internal or external:
"An internal DSL is simply an extension of an existing general-purpose language. You can think of an internal DSL as simply being a set of functions, data structures, and conventions applied to an existing language, such as C++ or Ruby.
This set of functionally is still specific to one problem domain. A typical internal DSL might be one used to define state transitions for AI using a set of query functions and a switch statement. Many games have implemented this kind of system in the game code in C++, as AI is often the responsibility of a programmer rather than a designer.
An external DSL is an independent language that has been entirely created for this specific purpose. Generally, a DSL program will be a text file, which is then interpreted (or perhaps compiled) by some part of the game engine or tool chain.
Again, AI is a common usage of a DSL-when programmers hand off AI to a designer, they will frequently make it more data-driven, often to the extent that they supply a 'little language' to script the AI transitions."
To create domain-specific language Whimsy, West defined his domain as the works of Rodney Alan Greenblat, using pieces from the artist's Elemental tour, a collection of semi-abstract paintings in a distinctive brightly colored and geometric style:
"The idea was this: If such a style of artwork were to be used in a video game, then it might be very useful to have a DSL that encapsulated that style and allowed for easy creation of similar pieces for use in-game.
The first step in creating a DSL is to get a rough idea of the elements that the domain comprises. Looking at the Elemental works, we can see a number of common aspects. There are concentric oval shapes, with petals adjoined to various sections.
Many of the works have segmented circles with colored circles inside them. There are little propellers and various other shapes that repeat both within individual works and within Greenblat's overall collection.
I decided the best way to approach creating this DSL would be to pick one piece and attempt to replicate parts of it. I chose the painting "Lunar Module" (see image). Many common elements hold the piece in its style: solid circles, concentric ovals with color gradients, petals, and stars."
You can now read the full technical feature
on Whimsy, Mick West's domain-specific language, which includes code and looks at potential uses of DSLs in games (no registration required, please feel free to link to this feature from other websites).