title: opengl distortion of push-popMatrix
body: <p>i have a "normal" opengl scene, and want to overlay this scene with a simple quad.</p>
  
  <pre><code>gl.glMatrixMode(GL_PROJECTION);
  gl.glPushMatrix();
  gl.glLoadIdentity();
  gl.glMatrixMode(GL_MODELVIEW);
  gl.glPushMatrix();
  gl.glLoadIdentity();
  gl.glTranslatef(-0.8f, 0.0f, 0.0f);
  // draw background
  gl.glBegin(GL_QUADS); // of the color cube
  gl.glColor3f(1.0f, 0.5f, 0.5f);
  gl.glVertex3f(0, 0, 1.0f);
  gl.glVertex3f(0.5f, 0, 1.0f);
  gl.glVertex3f(0.5f, 0.5f, 1.0f);
  gl.glVertex3f(0, 0.5f, 1.0f);
  gl.glEnd();
  gl.glMatrixMode(GL_PROJECTION);
  gl.glPopMatrix();
  gl.glMatrixMode(GL_MODELVIEW);
  gl.glPopMatrix();
  </code></pre>
  
  <p>as u can see on the screenshot, the new matrix is distorted. the colored lines are the axes.</p>
  
  <p><img src="https://dl.dropboxusercontent.com/u/11047616/opengl_distortion.jpg" alt="">
  <img src="https://dl.dropboxusercontent.com/u/11047616/opengl_distortion2.jpg" alt=""></p>
  
  <p>Now the question: How can i set an aspect ratio (like in gluPerspective) for my matrix to render a correct squad?</p>