POV Ray Tracer

• I want to take a quick look at a ray tracer.
• Angel describes ray tracing as
  • "a logical extension to rendering with a local lighitng model".
  • In lighting we discussed how our lighthing model was "cheap and easy" but not realistic.
  • In ray tracing we attempt to produce "photorealistic" images by tracing rays from a camera through the view plane to objects, and eventually to light sources.
  • 
    • for each pixel in the scene
      • Cast a ray from the camera through the pixel into the scene.
      • If the ray intersects with an object
        • Cast a ray from the intersection point to each light
        • If there are no intersecting obejcts, coupute the light using a lighting equation.
        • If the surface is "shiny", cast another ray along the angle of reflection
        • If the object is transparent or translucient allow the ray to travel through the object.
  • Object ray instersection computations are the major expense
    • Essentually every ray needs to check for an intersection with every object.
    • This is expensive
    • It is made faster by bounding box tests
• My choice is povray
  • It has been around forever
  • It is free and open source
  • LOOK at the pictures.
• It uses a scene description language to create images
  • Almost everything we have learned in graphics applies
    • Transformations
    • Camera deteail/ projectioni
    • lighting details
• Ray tracing is parallelizable and pov supports parallelism.
• The language is turing-complete - it is a "real" programming language.
• It is cross platofrm (Macs, Windows, Linux,) and open source.
• A quick look:
  • I stole this file from wikipedia.
  • But I have messed with it.
  • // and /* */ comments
  • There are a number of include files.
    • #include <stones.inc>
    • ls /usr/share/povray-3.7/include
    • Only ten levels deep!
  • Objects are declared and properties are set.
    • Every scene needs a camera object.
    • Coordinates as opengl but positive z goes into the screen.
    • There are many different built in projectsions
      • Orthographic
      • Perspective
      • fisheye