This series of Experiments with Shaders explores several variations of
a simple fragment shader that are used to provide colourful,  at times
rather psychedelic, backgrounds for performances.

The shader kernel is based on WyldAnimal's 2DShader-0001.fsh,  but  it
now bears very little resemblance to the original  although  it  still
uses the same basic algorithm and it produces similar output when used
with its default parameterisation.

Some initial experiments soon showed that it was an extremely  tedious
excercise to generate more than a small number of variations  by  just
editing the fragment shaders and scene files using them by hand.  This
being especialy so when improvements were being retro-fitted into  any
older versions.  To  overcome  this the approach taken was to create a
generic kernel that could be tailored using a number of parameters.

The initial intension was to use a scheme in which the kernel was used
via an include directive in a shader fragment file of the form

     #define parameter1 value
     #define parameter2 value
         etc.
     #include TheEmu-A.fsh-kernel

but although #define is by the shader language #include is not, so the
kernel and its tailoring parameters have to be in a single file.

Rather than maintain several copies of the sahder kernel I use I use a
simple script file to concatenate it with each set  of  parameters  to
create the set of .fsh files and .scn files using them.

Refer to comments in the script file and in the shader kernel for  how
to use them, but note that the details may change significantly as the
system used to generate the scenes matures. A more formal guide may be
prepared at a later date.