"Tim Nikias" <tim### [at] gmxde> wrote in message
news:3d480dce@news.povray.org...
> I've found that the "pattern image function" will
> switch up and down of an image. It uses the
> section from <0,0,0> to <1,1,0>, and <1,1,0>
> will be, on a heightfield, the foremost right
> corner, when looking from -z towards z.
> (Hope that explains something... Think about it)
>
> So, in effect, you might be using different
> parts of your pattern (not the y-planar
>  <0,0,0> to <1,0,1>, but the z-planar), or
> its used upside down. Don't know for sure though.

Yes, that was it. I found another little phenomenon.  The attached images
(sorry for the terrible jpg artifacts) show hfs of the same function.
TPGenTestE.JPG uses an external hf image whereas TPGenTestI.JPG uses the
internal type, both at the same res (512x384). As can be seen, the lumps in
the internal one have a much sharper, less rounded shape.  Do they interpret
the input image differently or perhaps the "pattern image function" uses a
different waveform.

-tgq

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Attachments:
Download 'TPGenTestI.JPG' (57 KB) Download 'TPGenTestE.JPG' (59 KB)

Preview of image 'TPGenTestI.JPG'

Preview of image 'TPGenTestE.JPG'

Another little phenomenon that I found out:
When creating a hf from an image with res m*n, the hf has a res of
(m-1)*(n-1), ie. each pixel represents a vertex on the hf (this is mentioned
in "6.5.1.5  Height Field"), this requires the input image I use to need an
"extra" row and column of pixels to join seamlessly.  However, with the
"function image pattern", this is not necessary.

-tgq

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In article <3d481ce5@news.povray.org>,
 "TinCanMan" <Tin### [at] hotmailcom> wrote:

> Yes, that was it. I found another little phenomenon.  The attached images
> (sorry for the terrible jpg artifacts) show hfs of the same function.
> TPGenTestE.JPG uses an external hf image whereas TPGenTestI.JPG uses the
> internal type, both at the same res (512x384). As can be seen, the lumps in
> the internal one have a much sharper, less rounded shape.  Do they interpret
> the input image differently or perhaps the "pattern image function" uses a
> different waveform.

Gamma correction of the external image? Maybe something with the 
color_map or waveform you used to generate the external image?

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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> Gamma correction of the external image? Maybe something with the
> color_map or waveform you used to generate the external image?

There it is, it was because my display_gamma was set to 1.8 in my .ini

-tgq

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