How to create 3D using 2D  Artists use the following depth cues to convey 3D impression  Size  Geometrical perspective  Shadow  Color

							  How to create 3D using 2D?
      Artists use the following depth cues to convey
       3D impression
          Size
          Geometrical perspective
          Shadow
          Color
          Sharpness
          Patterns
          Overlay (interposition)
However, they are intrinsically ambiguous, can be interpreted in
many ways. We interpret in the most likely possibility.
A counter example: impossible triangle




developed by Roger Penrose and his father
         One of Escher's
         marvelous impossible
         buildings. The basis
         of the illusion is the
         inclusion of the
         impossible triangle
         or tri-bar.
Escher
   Escher also used this principal in
    Ascending/Descending, The Impossible Staircase. The
    triangle is placed into the picture three times. As you
    look at each part of the construction in the print you
    cannot find any mistakes, but when the print is
    viewed as a whole you see the problem of water
    traveling up a flat plane, yet the water is falling and
    spinning a miller's wheel. How do the two towers
    appear relatively the same height yet the left side
    rises three stories and the right two? Why did Escher
    chose to use underwater plant life, greatly magnified,
    as his choice for an above watergarden? The illusion
    in this print, when viewed by most people, is not
    seen on the first look.
Size
   Smaller objects are more distant, and
    closer objects are larger.
   However
       Movie producers use this to fool us: take a
        close picture of miniature models to get an
        illusion of the distance objects or vice
        versa. “Honey, I shrunk the kids”
       Architects: using smaller window at higher
        floors.
Geometrical perspective
   Parallel receding lines appear as if they
    are coming together. (rail road tracks,
    light rays from the sun)
   In architecture
       Narrower towards the top or the other end.
   In art
       Da Vinci’s “last supper”
Shadow
   Shadows are extremely important in
    providing us the 3D impression.
   Light color appears closer to us and
    hence bigger.
Variations in Color
   Distant landscapes tend to lose their color
    contrasts. Colors get duller, less pure.
   A color print seems to have more depth than
    the identical picture printed in black and
    white, and shadows can be conveyed without
    variation in brightness.
   Distant mountains appear blue due to the
    blueness of the intervening air.
Variations in Sharpness
   Distance objects appear fuzzier, less
    sharply focused. Images are smaller in
    the retina. (oil painting)
   Artists convey the feeling of depth by a
    loss of detail in distant objects.
Patterns
   An abstract pattern may create the
    feeling of depth.
   Use by Vasarely and Mattise in
    paintings.
Overlaying
   We perceive one object to be farther
    than another if the second object blocks
    our view of the first.
   However, the apparently more distant
    object may in fact be closer but cut in
    such a shape that it fully reveals the
    apparently closer (but actually farther)
    object.
Previous knowledge
   You interpret an image according to the
    previous knowledge stored in your
    brain. An interpretation against
    common experience is suppressed.
       Inside-out face (Disneyland)
       Cube
       Stairs