"clipka" <nomail@nomail> wrote:
> "Kenneth" <kdw### [at] earthlinknet> wrote:
> > When a function is used in the HF_Square macro in shapes.inc--supposedly the
> > 'equivalent' of POV's regular HF--the function (whether of a
> > pigment/pattern OR an image_map) actually evaluates the pattern 'slice'
> > on the X/Z plane(!) rather than the X/Y plane as it is supposed to. That
> > explains lots of things!
>
> No, that's actually documented:
>
> "The function values used for the heights will be taken from the square that
> goes from <0,0,0> to <1,1,0> if UV height mapping is on. Otherwise the
> function values will be taken from the points where the surface is
> (before the deformation)."

So *that's* what is meant by that paragraph. I've been trying to pin down its
meaning for quite awhile... the 'surface' thing.  Now that you bring it to my
attention (and explain it so succinctly), it does make complete sense.

Hmm. I've been taking my cues from two different places--"3.5.11.16  Function
Image" (which I understand to be the way to create a 'regular' procedural HF,
and where the image 'slice' is definitely evaluated on the X/Y plane) and
"3.7.12.1.1  The HF Macros" in shapes.inc. It's possible that I've been
combining/confusing their explanations; I need to step back and re-gather my
thoughts.
>
> As the HF_Square macro will build a height field over the X/Z plane, you'd
> need to set the UseUVheight parameter to true to get the samples from
> the X/Y plane.
>
> The regular height_field is always in "UseUVheight" mode, so to speak.

I think this is why it never occurred to me, re: the HF_Square macro--I was
expecting it to automatically be in that mode as well. Hmm, what a strange and
semi-confusing difference. I can't truly understand why the macro wasn't set up
'out of the box' to duplicate regular HF behavior. (Probably having to do with
the added feature of UV-mapping, I suppose.) Thanks for pointing this out; much
appreciated.

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