       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 dull and 1.0 is the most shiny.

              scale  describes  how  much the texture coordinates
              should be scaled before applying the wood  texture.
              The larger the scaling, the smaller the area of the
              wood texture associated with a given  area  of  the
              surface.   A  large  number  results in a very fine
              pattern, a small number yields  a  coarse  pattern.
              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.
