GuruBlog : Articles about ruby

Curling Animation II

2010-08-22T14:02:35+02:00

I made another animation with Context Free Art and a small ruby script. The scroll down to see the sourcecode I have used for this file. This animation uses the same technique i used for my first one

Curling Recursion 2 from Nikolaus Gradwohl on Vimeo.

Blinking Logfile Map

2010-06-05T18:17:00+02:00

I always wanted to see where the readers of my blog are comming from, so I took a picture frame and inserted a world map, a handfull of leds and an arduino. Some soldering and some rubyscripts later I had my hardware geo-aware logfile visualization.

I have a script running at the server that parses new ip adresses from the log file and geocodes them. Than the continent code is sent to my mac where i have a little script that forwards the continent code to the serial port. And finally the arduino in the picture frame is making the leds blink. The whole project was hacked together as a weekend project so the scripts might need some "fine-tuning" :-)

This is my day 5 project for 30DaysOfCreativity

so please read my blog to make the leds blink :-)

Curling Recursion

2010-06-03T10:30:00+02:00

I made this animation with Context Free Art and a small ruby script. The scroll down to see the sourcecode I have used for this file

Curling Recursion from Nikolaus Gradwohl on Vimeo.

Set operations on ruby arrays

2009-11-28T05:23:00+01:00

Ruby provides some very interesting set operations on arrays.

given the two arrays A and B wich look like this

A = ["A", "B", "C", "D"]
B = ["C", "D", "E"]

There are three set operations we can use that union, intersection and difference.

Union

A | B

contains all elements from both sets without doublicates. So this results in ["A", "B", "C", "D", "E"]

Difference

A - B

contains all elements from set A that are not in set B. So this results in ["A", "B"]

Intersection

A & B

contains all elements that are in set A and in set B. So this results in ["C", "D"]

Ruby Caldav Library 0.3

2009-11-07T07:14:00+01:00

have made a new version of my ruby caldav lib.

version 0.3 is a bugfix release, to make it work with the kde4 calendar

Mapping linux input events to OSC

2009-09-06T04:48:00+02:00

In linux every input device registers under /dev/input/eventX and sends events in 16 byte blocks. these data chunks contain a timestamp the event type, the event code and a value depending on the event type the semantic of value changes. for a event type 1 (key event) value 1 means pressed and value 0 mean released.

here is a little ruby program that reacts to key press events and sends osc messages. which could trigger drum sounds, start play back, ...

key press events are not only sent by keyboards but also by mice, joystics, gamepads, a DDR mat, a buzz buzzer, ...

the code example is used to map keys of my PS3 Controller to drum sounds.

require 'osc';

c = OSC::UDPSocket.new

hh = OSC::Message.new('/drum', 's', "hh" )
bd = OSC::Message.new('/drum', 's', "bd" )
sn = OSC::Message.new('/drum', 's', "sn" )

File.open("/dev/input/event7") do |f|
  while true
    event = f.read(16).unpack("llSSl")
    time = event[0] + event[1] / 1000000.0
    type = event[2]
    code = event[3]
    value = event[4]

    puts "Ti: #{time} T: #{type} C: #{code} V: #{value} " if type == 1

    c.send( bd, 0, 'localhost', 3334 ) if type == 1 && code == 298 && value == 1
    c.send( sn, 0, 'localhost', 3334 ) if type == 1 && code == 293 && value == 1
    c.send( hh, 0, 'localhost', 3334 ) if type == 1 && code == 303 && value == 1
  end
end

The code was inspired by 2 articles i found recently the first one is about how to use a DDR-mat to trigger Drum Sounds and the second one shows how to read the accelerometer data from a openmonoko phone

ruby osc seqencer version2

2009-04-13T14:57:00+02:00

i updated my osc sequencer in ruby. now it doesn't just send osc events but also react to it. i made a small processing sketch that sends osc play,pause,stop events for each track in the sequencer. i also refactored the ruby code a bit, to use classes. next steps i plan are to separate the sequencer code from the sequences and allow sequences to be added or deleted at runtime via osc messages.

the code isn't very reusable now, so i still considere this more as a prove of concept, but i like the idea of separating the frontend and the backend via osc events and having sequences that can run independently.

that should enable some nice osc controlled audio/video installations.

write me a comment or mail if you have some ideas for improvement or if you use the code in one of your projects

processing ical-flowers-2.0

2009-02-15T08:15:00+01:00

I made a new version of the ical flowers sketch i wrote in dezember. This time it doesn't only show a flower for every event in my calender, it also shows

the current weather (using the rubyweather library)
the current temperature outside
the min/max temperature outside
the current temperature inside ( using my arduino i2c thermometer sketch)
the sky color changes depending on the current time

the system consists of a ruby-proxy, an arduino sketch and a processing sketch.

the ruby proxy starts a web-server on port 2000. It fetches the current weather using the rubyweather gem, fetches the events from the configured caldav calenders, and fetches the current temperature from the arduino using ruby-serial

the arduino sketch is basicaly the same as in this blog post. the only change is that the arduino only sends the temperature when the host sends a 'C' over the serial line

the processing sketch finally fetches the data via http from the proxy and displays it ( using my icap4p library. the screen is updated every 1/2 hour using the method described here

the code can be downloaded here

it's published under the LGPL

have fun :-)

ruby symbols vs string vs constant

2009-02-10T03:13:00+01:00

on saturday i was asked by a ruby-newbie (sorry - i had to write it :-) ) whats the difference between a symbol, a string and a constant in ruby. even tough there are realy, realy many articles about ruby symbols ( a google search for "ruby symbols" results in 1,340,000 hits - so this is the 1,340,001 aricle covering the topic) there is obviously still some confusion out there. So i try my own definition here.

Ruby Caldav Library 0.2

2009-01-28T04:16:00+01:00

I have made a new version of my ruby caldav lib.

version 0.2 is a bugfix release, there are no new features but i removed some essential typos