## Basic Scene Requirements

Unlike some other ray tracers out there, Tachyon requires that you specify most of the scene parameters in the scene description file itself. If users would rather specify some of these parameters at the command line, then I may add that feature in the future. A scene description file contains keywords, and values associated or grouped with a keyword. All keywords can be in caps, lower case, or mixed case for the convenience of the user. File names and texture names are normally case-sensitive, although the behavior for file names is operating system-dependent. All values are either character strings, or floating point numbers. In some cases, the presence of one keyword will require additional keyword / value pairs.

At the moment there are several keywords with values, that must appear in every scene description file. Every scene description file must begin with the BEGIN_SCENE keyword, and end with the END_SCENE keyword. All definitions and declarations of any kind must be inside the BEGIN_SCENE, END_SCENE pair. The RESOLUTION keyword is followed by an x resolution and a y resolution in terms of pixels on each axis. There are currently no limits placed on the resolution of an output image other than the computer's available memory and reasonable execution time. An example of a simple scene description skeleton is show below:

    BEGIN_SCENE
      RESOLUTION 1024 1024
    ...
    ...  Camera definition..
    ...
    ...  Other objects, etc..
    ...

    END_SCENE