For the Slope pattern:

1) It is mentioned (section 6.7.11.30) that the slope direction will usually
be <0,-1,0> for landscapes.  It was not intuitive to me at first why this
would be used rather than <0,1,0>.  I suppose it is to condition the output
value from "slope".  You might want to explain this further for the benefit
of newbies (myself included).

2) When I went to the "Slope" documentation (section 6.7.11.30) I was taken
straight to the section without of course passing the "parent" section
(6.7.11).  Without the context of the Pattern commentary I was a little
confused for a while on exactly how Slope was to be used. Now that I
understand it, going back over the documentation I feel stupid for not
seeing how obvious the description is now. It might have helped me as a
first-time reader of section 6.7.11.30 if I was reminded that Slope is a
pattern much like onion or gradient and can be used in a texture_map (for
example) like in the following example:

  texture {
    slope { <0,-1,0>, 0.0, 0.5}
    texture_map {
      [0.0 pigment {color rgb <224/256,224/256,197/256>}]
      [0.3 pigment {color rgb <224/256,224/256,197/256>}]
      [0.4 T_Grnt27 scale 0.0001]
      [1.0 T_Grnt27 scale 0.0001]
    }
  }

I think this would have gotten me to "where I wanted to be" much quicker.

Just my $0.02.

Best regards,

Jon Berndt

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