Robot Has No Heart

Xavier Shay blogs here

A robot that does not have a heart

Introducing SocialBeat (screencast)

Here is a screencast of socialbeat in which you will note:

  1. I don’t appear drunk
  2. I don’t reveal intra-company communications
  3. I show off the full gamut of socialbeat’s awesomeness in under 3 minutes

In these ways you may find it superior to other screencasts you may have seen on the matter.


Introducing SocialBeat

If you are behind the times – socialbeat is some code that lets you live code OpenGL visualizations to MIDI tracks.

OpenGL Text with Imlib2

Getting text into your openGL apps is simple with the use of the imlib2 library (developed by the enlightenment team). If you have the good fortune of working on a debian system, the libraries are in apt:

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sudo apt-get install libimlib2-ruby

The examples at the ruby bindings webpage show the basics of loading an image and writing text, all that remains is converting an Imlib2::Image into an OpenGL texture – just switch the data around from BGRA to RGBA…

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class Imlib2::Image
  # Convert data to format compatible with OpenGL
  def rgba_data
    new_data = Array.new(data.size)
    i = 0
    for i in (0..data.size/4-1)
      new_data[i*4] = data[i*4+2] 
      new_data[i*4+1] = data[i*4+1]
      new_data[i*4+2] = data[i*4+0]
      new_data[i*4+3] = data[i*4+3]
    end
    return new_data.pack('C*')
  end
end

... and you can pass it straight into GL::TexImage2D. Follows is the TextMananger class I wrote tonight. Still haven’t quite mastered imlib2 – note the resize hack to get the correct format. If anyone has any suggestions I’m all ears.

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require 'imlib2'
 
class OpenGLTextManager
  def initialize
    @textures = Hash.new
 
    blank_filename = 'res/img/blank.png' # 1x1 png image
    @blank = Imlib2::Image::load(blank_filename)
 
    # Probably better to copy the font locally and load it from there
    Imlib2::Font::add_path '/usr/share/fonts/truetype/ttf-bitstream-vera'
    fontname = 'Vera/10'
    
    @font = Imlib2::Font.new(fontname)
  end
  
  def render text, x, y
    texture = @textures[text]
    texture = create_texture(text) if texture == nil
 
    # Draw a quad with the text texture
    # Looks best with Ortho 1:1 projection
    GL::Enable(GL::TEXTURE_2D);
    GL::LoadIdentity();
    GL.BindTexture(GL::TEXTURE_2D, texture.ogl);
    GL::Begin(GL::QUADS);
        GL::TexCoord(0.0, 0.0); GL::Vertex(x, y)
        GL::TexCoord(0.0, 1.0); GL::Vertex(x, texture.height + y)
        GL::TexCoord(1.0, 1.0); GL::Vertex(texture.width + x, texture.height + y)
        GL::TexCoord(1.0, 0.0); GL::Vertex(texture.width + x, y)
    GL::End()
  end
 
  def create_texture text
    fw, fh = @font.size(text)
 
    # This is a hack
    # Image.new doesn't have the right color format (or something),
    # so just resize a preloaded png
    image = @blank.clone
    image.crop_scaled! 0,0,image.width, image.height, fw, fh
    image.fill_rect [0,0], [image.w, image.h], Imlib2::Color::RgbaColor.new(0,0,0,255)
 
    image.draw_text @font, text, 0, 0, Imlib2::Color::WHITE
 
    texture = TextTexture.new
    texture.ogl = GL::GenTextures(1)[0];
    GL.BindTexture(GL::TEXTURE_2D, texture.ogl);
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_S, GL::CLAMP);
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_T, GL::CLAMP);
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MAG_FILTER,GL::LINEAR);
    GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MIN_FILTER,GL::LINEAR);
    GL.TexImage2D(GL::TEXTURE_2D, 0, GL::RGBA, image.width,
                  image.height, 0, GL::RGBA, GL::UNSIGNED_BYTE, image.rgba_data);
    texture.width = image.width
    texture.height = image.height
    image.delete!
    @textures[text] = texture
    return texture
  end
 
  def get_texture text
    texture = @textures[text]
    texture = create_texture(text) if texture == nil
    texture
  end
end
 
class TextTexture
  attr_accessor :ogl
  attr_accessor :width
  attr_accessor :height
end
 
class Imlib2::Image
  # Convert data to format compatible with OpenGL
  def rgba_data
    new_data = Array.new(data.size)
    i = 0
    for i in (0..data.size/4-1)
      new_data[i*4] = data[i*4+2] 
      new_data[i*4+1] = data[i*4+1]
      new_data[i*4+2] = data[i*4+0]
      new_data[i*4+3] = data[i*4+3]
    end
    return new_data.pack('C*')
  end
end

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# Usage
# ... Inside draw loop ...
GL::MatrixMode(GL::PROJECTION);
GL::LoadIdentity()
GL::Ortho(0,@viewport.x,@viewport.y,0,-1.0,1.0)
                
GL::MatrixMode(GL::MODELVIEW);
GL::LoadIdentity()
GL::Disable(GL::LIGHTING);
GL::Disable(GL::DEPTH_TEST);
   
GL::Color(1.0, 1.0, 1.0, 0.7);
OpenGLTextManager.new.render 'hello', 0, 0
A pretty flower Another pretty flower