Introducing SocialBeat (screencast)

2008-11-03T20:02:00Z

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

I don’t appear drunk
I don’t reveal intra-company communications
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.

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

OpenGL Text with Imlib2

2006-04-20T23:43:00Z

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:

1	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…

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.

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

# 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

Opengl - Xavier Shay's Blog

Introducing SocialBeat (screencast)

OpenGL Text with Imlib2