The Experiments with Flags scenes comprise a set of simple scenes in
which the main elements are flags.  They  are  built  around a large
collection of world flags released under a Creative Commons  licence
and downloaded from

      http://www.free-country-flags.com/ 

In addition to using the flags I have also used these experiments to
begin exploring the use of vertex shaders,  though  not to any great
depth, and simple silhouettes.

The scenes are grouped in the following series

   A - Flags used as static backdrops for a single performers.

       The only difference between this and using a  simple
       background is that a number of flags are selected at
       random to dorm the backdrop.

   B - Flags used as static backdrops for a multiple performers.

       The performers are arranged in a regular grid and 
       each has a flag as an individual backdrop.

   C - Flags used as moving backdrops for a single performers.

       As A but a vertex shader is used to introduce some
       movement to the flags.

   D - Flags used as a static screen before a single performer.

       Similar to A but the flags are placed in front of the
       performer who can be seen through them. The screen is
       made translucent by lowering its opacity.

   E - Flags used as a moving screen before a single performer.

       As D but a vertex shader is used to introduce some
       movement to the flags.

   F - Flags used as a static screen before a single performer.

       Rather than making the flag translucent it has been
       perforated by an array of small holes. Several test
       scenes are also included.

   H - Flags used as a foreground for silhouettes.

       This is not really flag specific, but flags do form
       a convenient background for silhouettes.

   G - Reserved for moving perforated flags.

   I - Flags used as a background for silhouettes.

       As H but the flags form a screen in front of the 
       silhouettes.

   J - A single flapping flag is used as a background.

       The flapping motion is produced using a  fragment
       shader to animate the flag.

       In one version the flag is randomly selected from
       the collection of world flags and in another  the
       clip name is used as a flag.

The lessons learned from these experiments are that the flags  themselves
are quite useful scene elements,  but  that  they are much more effective
if they are animated. However, using vertex shaders to animate them  does
not always lead to good results with this sort of scene  element  because
of the straight lines commonly found on flags get mapped to a  series  of
straight line segments by applying a vertex shader so the ripples in  the
flag look angular instead of smooth. This can be easily seen in the scene
with a single moving flag if the flag is a tricolour.  It may be possible
to decrease the angularity by increasing the number of vertices,  i.e. by
increasing the resolution specified for each node, but only by increasing
the vertex count by a large factor and this uses a lot of CPU/GPU power.

The simple mechanism of lowering the opacity of a flag in order to use it
as a translucent screen in front of a performer works  but  is  not  very
satisfactory as it produces rather dull scenes. Better looking, brighter,
results are obtained by using a shader to punch holes in the flag.

Much better looking flag motion can be obtained using fragment shaders as
can be seen in the examples that do this. The particular shader used here
is very simple and the results are not fully realistic,  though  they are
much better than those using the vertex shader, but it should be possible
to improve on them if more realism is ever required.