Using pure (gem) ruby libraries with ruby-processing

Now you can create your own ruby libraries, and it relatively easy to include them, but what about using external gems? Well essentially what you are looking at is, can the library be used from jruby, if so you can probably use it with ruby-processing? The simplest way is to just to set the GEM_HOME environmental variable

export GEM_HOME=/var/lib/gems/1.9.1 (worked for me on ubuntu linux)

If this doesn't work for you then you could install your gems using jruby.

jruby -S gem install rake (etc...)

But to be extra safe you should probably install ruby-processing the same way

jruby -S gem install ruby-processing

Further belt and braces stuff to run sketches you should probably start ruby-processing from jruby using the --ruby flag

jruby -S rp5 run --jruby sketch.rb

Here is one such sketch

require 'perlin_noise'

attr_reader :md, :points, :p, :n2d

def setup
  size(800, 600)
  @n2d = Perlin::Noise.new 2, :curve => Perlin::Curve::CUBIC
  md = false
  @points = []
  background(255)
  smooth(8)
end

def draw
  if (md)
    500.times do
      points << Point.new(rand(0 ... width), rand(0 ... height))
    end
  end
  noise_detail(8,0)

  (points.size - 1).downto(1) do |i|
    @p = points[i]
    p.update n2d
    if (p.finished)
      points.delete_at(i)
    end
  end
  # puts(points.size)
end

def mousePressed
  @md = true
end

def mouseReleased
  @md = false
end

def keyPressed
  background(255)
  (points.size - 1).downto(1) do |i|
    @p = points[i]
    points.delete_at(i)
  end
end

class Point
  include Processing::Proxy

  MAX_SPEED = 3000000

  attr_reader :finished, :x, :y, :xv, :yv, :width, :height

  def initialize(x = 0, y = 0)
    @x, @y = x, y
    @xv, @yv = 0, 0
    @finished = false
    @width = $app.width
    @height = $app.height
  end

  def update n2d
    stroke(0, 16)
    @xv = cos(n2d[x * 0.01, y * 0.01] * TWO_PI)
    @yv = -sin(n2d[x * 0.01, y * 0.01] * TWO_PI)

    if ((x > width) || (x < 0))
      @finished = true
    end

    if ((y > height) || (y < 0))
      @finished = true
    end

    if (xv > MAX_SPEED)
      @xv = MAX_SPEED
    else
      @xv = -MAX_SPEED if (xv < -MAX_SPEED)
    end

    if (yv>MAX_SPEED)
      @yv = MAX_SPEED
    else
      @yv = -MAX_SPEED if (yv < -MAX_SPEED)
    end

    @x += xv
    @y += yv

    line(x + xv, y + yv, x, y )
  end
end

Note with this sketch you would probably be better off using processing perlin noise