Raypaint reads a rayshade input file and opens a graphics window into
which the image is progressively rendered.  Graphics support routines
are provided for X11 and GL (SGI / RS6000).  Note that raypaint displays
a greyscale image when running under X.

Command-line arguments to raypaint are identical to rayshade arguments.

By default, raypaint refines areas of the image that it considers
"interesting" (largish and contrasty).  The mouse may be used to direct
raypaint to concentrate on particular regions.  Holding down the
left mouse button causes the indicated region to be single-sampled down
to the pixel level.  The right button causes the region to be supersampled.
When either button is released, raypaint continues to refine by
either single-sampling (if the left button was pressed) or supersampling
(if the right button was pressed).  If either button is pressed while the
cursor is pointing at a region that has already been resolved to the
pixel-level, raypaint will instead choose its own region to refine.

The middle mouse button may be used to sweep out a rectangular region to
which raypaint should restrict its refinement:  Press and hold the middle
mouse button while pointing at one corner of the region of interest,
drag the cursor to the opposite corner and release the mouse button.
Note that no rectangle will be drawn.  Refinement will continue inside
of the indicated region.

When every pixel has been sampled, an image file is written.

Note that raypaint is intended to be an example application, not a
polished tool.  You are encouraged to tear apart raypaint to improve
it or build your own application.

To compile, move either xgraphics.c (X11) or glgraphics.c (SGI) to
graphics.c, edit the Makefile and change GRAPHICSLIB to reflect your
choice of graphics support, and run make.