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"Bald Eagle" <cre### [at] netscape net> wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
>
> > In looking at your results I'm not at all sure why the max extent values
> > for x and z are all zero? The HF max extent should be 1 or larger for x
> > and z (always I think if not scaled) ?
>
> This got me curious as well.
>
> So I just threw some quick lines of code together.
>
> The hf looks fine to me. Typo in Ken's code?
>
Oooh, yet another one! You're absolutely right, I screwed up my #debug
statements, a cut-and-paste error from running so many tests. I never actually
used my max_extent values. :-[ So sorry. That was a real whopper of a mistake.
My apologies to William P for 'chasing this down a rabbit hole'.
Using my now-corrected code, these are today's results:
function 500,500 {0}
MIN_EXT = <0.0000000000, -0.0000000153, 0.0000000000>
MAX_EXT = <1.0000000000, 0.0000000153, 1.0000000000>
--- BTW: For a somewhat quicker test, the HF could use function 2,2 {0}
instead; the resulting planar HF still looks fine as an object, and also
produces the speckles vs. no-speckles comparison.
> 1/pow (2, 16) = 0.00001526
That's fascinating; I didn't realize that my 'jump' point had a computational
basis. Thanks!
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William F Pokorny <ano### [at] anonymousorg> wrote:
> Perhaps worth saying a little more than the above. Whether creating a
> height_field or internal image_map from a function in POV-Ray, any
> 'function return' values outside the [0-1] get 'wrapped' to a ramp wave
> as is the default with the majority of inbuilt patterns.
>
> So, function return values of:
> -0.1 --> 0.9
> -0.5 --> 0.5
> -0.9 --> 0.1.
> 1.1 --> 0.1
> 1.5 --> 0.5
> 1.9 --> 0.9
I will just point out that this is not currently documented anywhere.
https://wiki.povray.org/content/Reference:Maps
is blank.
If anyone wanted a quick 10-15 min project, writing a scene with a simple 0 --->
x color map and a loop, function, gradient pigment, or similar and showing that
the color_map value.x is modulo-wrapped would be great.
Numeric output via #debufg or file, or a graph showing Color.x would be nice.
- BE
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And actually, there seems to be some potentially conflicting information in the
documentation.
https://wiki.povray.org/content/Documentation:Tutorial_Section_2.2
"For every position in POV-space, a pattern returns a float value in the range
from zero to one. Values outside the zero to one range are ignored."
Presumably if a pigment pattern was wrapped in a function, one could then have
access to the actual values emitted, and either graph them or just run tests to
detect the presence of values <0 or >1.
- BE
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