       SippShaderWood ambient specular c3 scale basecolor ringcolor [opacity]
              This  shader  creates a simulated wood texture on a
              surface.  It uses  two  colors,  one  as  the  base
              (often  lighter)  color  of the wood and one as the
              color of the (often darker) rings in it.  The rings
              is put into the base color about the x-axis and are
              then distorted using noise()  and  turbulence().  A
              similar pattern is repeated at regular intervals to
              create an illusion of logs or boards.

              ambient is a value between 0.0 and 1.0 which deter-
              mines  how much of the base color of a surface that
              is visible when it is not illuminated by any  light
              source.

              specular  is  a  value between 0.0 and 1.0 which is
              the fraction of color specularly reflected.

              c3 is the shininess of the surface where 0.0 is the
              most shiny and 1.0 is the most dull.

              scale  is a factor which determines the size of the
              wood pattern depending on the size of  the  texture
              coordinate  system in relation to the world coordi-
              nate system. You will have to  experiment  some  to
              get this right.

              basecolor  is  a list containing the red, green and
              blue values for the wood base.  Each being a number
              between 0.0 and 1.0.

              ringcolor  is  a list containing the red, green and
              blue values for the wood rings.

              opacity describes the opacity  of  a  surface.  0.0
              means   totally   transparent,  1.0  means  totally
              opaque.  May be a list of red, green and blue opac-
              ity  values  or  a  single value to be used for all
              color channels.  Optional, default is 1.0.
