title: OpenGL/OpenTK Fill Interior Space
body: <p>I am looking for a way to "fill" three-dimensional geometry with color, and quite possibly a texture at some time later on.</p>
  
  <p>Suppose for a moment that you could physically phase your head into a concrete wall, logically you would see only darkness. In OpenGL, however, when you do this the world is naturally hollow and transparent due to culling and because of how the geometry is drawn. I want to simulate the darkness/color/texture within it instead.</p>
  
  <p>I know some games do this by overlaying a texture/color directly over the hud--therefore blinding the player.</p>
  
  <p>Is there another way to do this, though? Suppose the player is standing half in water; they can partially see below the waves. How would you fill it to prevent them from being able to see clearly below what is now half of their screen?</p>
  
  <p>What is this concept even called?</p>