Context free art in ruby in 3d in opengl

Since I'm a fan of contextfreeart.org and nodebox.net, I've made a small ruby program inspired by contextfreeart, using context free grammars in 3d with opengl. The only operations right now are:

• cube - create a cube.
  
• up/down/left/right/to/from(rule) - define what rule to continue with in the specified direction.
  
• flip - rotate 90 degress
  
• scale - scale with 0.9.
  

But it should be quite easy to add new primitives (and clean up the code). Here is an example of a tree. Install ruby-opengl gem, click and move mouse to rotate, q - new random seed value, w - increase rendering depth, e - decrease rendering depth.

load 'cfa3d.rb'
class Tree < CFG
  rule :start do |s|
    s.cube
    s.up :x
  end

  rule :x do |s|
    s.cube
    s.right :x
  end
  rule :x do |s|
    s.cube
    s.flip
    s.left :x
  end
  rule :x, 0.1 do |s|
    s.cube
    s.flip
    s.right :x
    s.flip
    s.left :x
  end
  rule :x do |s|
    s.cube
    s.scale
    s.up :x
  end
end

render Tree

A keyhandler for svg

This is an example of a keyhandler for controlling an application in svg. It consists of three files.

class.js. This is an implementation of classes in javascript, ripped out of prototype's html guts and modified.
keyhandler.js. A class that propagates key-events between javascript objects and their corresponding svg-elements. Currently it only changes the fill color of the focused element to green.
example.svg. The demo svg with some simple svg-elements that you can switch focus between with left/right/up/down. Press enter to get the currently selected item.

A javascript object that can get key focus has the following properties:

• It has a variable named dom that refers to a svg-element.
  
• It can have the functions onFocus and onLeaveFocus that are called when it gets or leaves focus.
  

The api of the keyhandler.

• setFocus(x) - give focus to object x.
  
• leaveFocus(x) - leave focus from x. this will also trigger leaveFocus on any children of x.
  
• addKey(x, "a", f) - add key listener function f (which is called in the scope of x) for key 'a' when x (or children of x that hasn't overloaded 'a') have focus.
  
• focusStrip([a, b, c], "left", "right") - specify that you can move focus between a, b, c by using the keys left and right.