   How is the frustum mapped to a unit cube?
  I went a few times over the theory and seem to not understand how this operation happens. I understand that when mapping the frustum to a unit cube a warping happens or distortion that is what we want when we perform perspective projections(farther objects appear smaller than near ones). Mapping projection from the frustum to the unit cube we can get the world on screen by simply an applying an ortographic projection. :D   