"John D. Gwinner" <jgw### [at] hotmailcom> wrote in message
news:3b49b802$1@news.povray.org...
> Ah, thanks - I'd been playing with the functions to see what the effect
was
> so that's probably where the x,z,y came from.
>
> I didn't think it was a bug exactly, I thought I was doing something wrong
>
> How would we isolate the bug?

Well, being the mere end-user that I am there's not much to try except make
sure the surface level changes along the y axis as a whole instead of just
the pattern changes one would expect.
I put a semitransparent y plane across the isosurface and placed the camera
nearly parallel with it to see if the surface really does rise and fall as a
whole.  It did.  The amount of shift is small but I believe what is
happening is that the function is somehow changing the color_map or isn't
remaining stable.
That is to say, perhaps it brightens and darkens overall instead of only
shifting the color values around in a prespecified range.  If you look at
the patterns themselves you will see the patterns like ripples or bozo (bozo
is especially obvious once animated) transform rgb 0 to rgb 1 while rgb 1
goes to rgb 0 along the pattern wave type.
We can only see the isosurface undulating though to prove or disprove
anything, since the patterns themselves as pigments look correct.
Try the script below if you like, I'm not absolutely certain wrinkles is the
only problemed pattern, granite looks awful when phased.  As Mike Williams
has said it could be all in how the pattern equations are done, something I
know nothing about.  But it looks as though all are subjected to the same
undulation of the isosurface and there isn't anything there I can figure to
cause it aside from phase.

Bob H.

> I was wrong about the news link, it's
> news:news.povray.org/povray.binaries.animations, "Rot and Renewal".  And
now
> that I check it, I had the x,z,y *lol*.  Back to the IDE ..

#version unofficial MegaPov 0.7;

#declare R=1.0;
#declare R1=R+0.01;
#declare Box = 1;

camera { location  <5*R, 0.1*R, -8*R> look_at <0, 0, 0> angle 20}

sky_sphere { pigment {
    gradient y
    color_map { [0.0 color blue 0.6] [1.0 color rgb 1] }
  }
}

plane {y,.05 pigment {rgbf .7}}

light_source {<100,200,-100> colour rgb 1}
light_source {<-100,200,100> colour rgb 1}

plane {y,0
            pigment {wrinkles // bozo // ripples // granite
        color_map {
                   [0   color rgb 0]
                   [1 color rgb 1]

        } sine_wave phase clock
      scale .3
    translate <1, 0, 0>
    turbulence .1
    }
   finish {ambient 1 diffuse 0}
 rotate -90*x
}

#declare WaveDepth = 1;

#declare WrinklesFunc =
function {
    pigment {wrinkles // bozo // ripples // granite
        color_map {
                   [0   color rgb 0]
                   [1 color rgb 1]

        } sine_wave phase clock
      scale .3
    translate <1, 0, 0>
    turbulence .1
    }
}

isosurface {
    function {
        y - WrinklesFunc(x,y,z) * WaveDepth/10

      }
    contained_by{box <-R,-R,-R> <R, R, R>}


    pigment {rgb <.2 .2 .9 >}
    finish {phong 0.5 phong_size 10}
}

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