From: anne001 <anne@...>
Date: 2006-03-07T21:43:41+09:00
Subject: Is the key delaying interpretation of a variable?

I am modifying robot.rb in opengl's sample directory,
the original robot turns, mine does not! snif...

The original example goes something like this
A display proc
display = Proc.new {
....
   GL.Rotate($shoulder, 0.0, 0.0, 1.0);
.....
}
a keyboard proc
keyboard = Proc.new {|key, x, y|
   case  (key)
      when 's'[0]
         $shoulder = ($shoulder + 5) % 360;
         GLUT.PostRedisplay();

Then you tell glut the name of those procs
   GLUT.DisplayFunc(display);
   Glut.KeyboardFunc(keyboard);

----------------------------------------------------------------------------
The new program goes like this
  def displaytree
....
    traversetree
....
  end

  def traversetree
   applytransform
....
  end

  def applytransform
 ...
   GL.Rotate(*@rotation);
 end
....
and in the initialization definition
@rotation = [$shoulder, 0.0, 0.0, 1.0]

   GLUT.DisplayFunc(lambda{trunk.displaytree});
   GLUT.KeyboardFunc(keyboard);
-------------------------------------------------------------
The first program rotates, the second one does not.
I am wondering if it has something to do with the 2nd method
estimating $shoulder in a different way from the first method?

@rotation is probably evaluated before creating the new object,
and after that this line is never accessed? So my display does not have

a $shoulder parameter to update?

scale=[2.0, 0.4, 1.0]
jointP=[-1, 0, 0]
translation=[$shoulderposx, $shoulderposy, 0.0]
rotation = [$shoulder, 0.0, 0.0, 1.0]
draw = Proc.new { GLUT.WireCube(1.0)}
upperarm = Node.new(scale, translation, jointP, rotation,&draw)

How can I keep the $shoulder parameter physically with all the other
parameters defining the shoulder  definitions, and still have $shoulder
 update with keyboard presses?