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variable: $blufact -- background blue tint
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default: 1.0 (neutral/gray)

The "blufact:" entry (F3 panel, middle right) has
a default value of 1.0.  Setting $blufact above
1.0 give the background gray brain surface a
bluish tint.  Setting it below 1.0 gives the
surface a yellowish (brownish) tint.

This is only visible with the curvature coloring
off (or in the narrow range of colors with it on
where the surface is gray when the curvature is
zero).

Use <Return> in the entry, or the REDRAW button
to see effects of a change.  In a script, use:

  do_lighting_model
  redraw

or, more simply:

  redrawbutton

