Setting up POV-Ray

   # add the computer graphics directory to your path
        set path = ($path /usr/local/units/cgha215/labs/bin/)
        setenv POVINI /usr/local/units/cgha215/labs/povray/povray.ini

Questions and Tasks

1. What does POV-Ray do which is different from OpenGL?

   Unlike OpenGL POV-Ray implements the physical modelling of light rays
   interacting with objects in the scene. This means you can do proper
   shadows, reflectivity and translucency, which you can't do with OpenGL.
   POV-Ray also allow you to add texture mapping, halos, surface finishes
   and bumps, complex objects generated from splines, and to use a whole 
   heap of other rendering techniques.
   

2. How do I run it? How do I look at the image it produced? What do all of the (see command line switches) do? What is a .ini file?

   You can run it using povray or x-povray. The difference is that x-povray
   can be made to generate an image in a window as it renders the scene. It
   will take a .pov scene file, render it and produce a .tga file.
   
   Some of the important flags are:
     +I            The .pov input filename (.pov is optional)
     +D0 +D1       Draw the image as the scene is being rendered
     +w640 +h480   Create an image which is 640x480
     +p            Pause after rendering and wait for user input.
   
   The .ini file is a configuration file which can be used set
   the command line options so we don't have to type them in 
   each time. Currently POV-Ray is set to use the 
   ~cgha215/labs/povray/povray.ini file. You can however use your own.
   If you do you'll have to remember to copy the Library_Path=
   lines from the povray.ini file to your own.
   
   An example invocation would be:
     x-povray +Ishapes +d1 
   This would render shapes.pov with povray.ini and create the file
   shapes.tga. It would also draw the image to the screen as it is
   rendered.
   
   If you wanted to use your own .ini file instead of povray.ini you would
   use:
     x-povray my_own.ini +Ishapes +d1
   

3. POV-Ray uses a left handed co-ordinate system. How is this different from OpenGL? How does it affect our rotations?

   In a left handed co-ordinate system the positive x and y directions
   are right and up respectively. The positive z direction is away from the
   viewer. OpenGL uses a right handed co-ordinate system. In OpenGL the
   positive direction is towards the viewer. 
   
   With a left handed co-ordinate system a positive rotation would be
   clockwise around the axis. This is the opposite of OpenGL.
   

4. Set up the camera and sphere by following the instructions in the html documentation about cameras and objects.

5. Add another shape such as a cone or cylinder (Simple Shapes) to your scene.

6. Change the surface finish of your sphere using the Surface Finishes documentation.

7. Finally, complete the light source section of the tutorial.

The rest of the documentation examples can be done at your leisure. They include more advanced objects, atmospheric effects, more textures, simple animation and other advanced rendering techniques.

There are also more example scenes in the povray directory (/usr/local/units/cgha215/labs/povray).

If there are any problems please email Philip Dunstan.