"Kenneth" <kdw### [at] earthlinknet> wrote:
>
> ...Adding rotate 180*x or scale -y corrects this (no
> translations needed)...
>
I've since noticed some behavior of this image_map-to-HF-function that makes the
situation more complex than I originally thought.  While the mirror-image
correcting trick does work, there is still an odd *scaling* problem regarding
the image_map.  If I scale the image_map smaller--in order to "tile" it across
the face of the HF--the scaling doesn't take place from the origin as it
normally would--x=0, z=0--but rather, from x=0,z=1! Strangely, that is the
defacto "origin" of the HF function. This causes havoc when trying to line up
an  equally-scaled image_map TEXTURE to the HF--they scale from different
origin points!

I did figure out a solution, though, that solves both the mirror image problem
AND this odd scaling. It involves putting all of the "corrections" OUTSIDE of
the HF function. (I couldn't find any other way to do it.)  Like so:

height_field{
   function 300,300{
        pigment{
            image_map{sys "my_image.bmp" map_type 0 interpolate 2}
            // the HF image shows an incorrect "mirror image"
            scale .65 // or whatever, to tile the image across the HF
               }
                   }
   scale <1,-1,1> // inverts height of HF to point at -y
   rotate 180*x // flips the HF over--corrects the mirror-imaging, and
                //re-orients the HF height to be in the correct +y direction
   translate 1*z // moves the HF back to its proper place at the REAL origin

   texture{..... scale .65} // an image_map here -- flipped 90*x as usual--
                            // will correctly line up with the HF, and
                            // everything scales together properly.

   scale ....  // additional scaling of entire HF
   translate...
            }

I would assume that using any regular POV pigment pattern in the HF
function--rather than an image_map there--would also exhibit these same
problems, and need the same corrections. Gradient y does; I tried it.

BTW, another odd thing here is that you can't use the ONCE keyword in the HF
function's image_map; no detail shows up at all, just a blank, flat HF. I don't
remember that happening with a normal HF.

Ken W.

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