"Kenneth" <kdw### [at] gmailcom> wrote:
> "LanuHum" <Lan### [at] yandexru> wrote:
> > Hello! I created a picture with a gradient. I want to use it as a
> > height map for a sphere. However, only gray stripes are visible on the sphere.
> >
>
> The 'flat' look of those gray stripes seems odd to me; there *should* be some
> (fake) 'depth' to them due to your bump_map, based on the normal-pattern image
> that you posted:
>
> normal{ bump_map{"/home/lanuhum/src/Thread_90.jpg"
> gamma 1.1000 map_type 0
> interpolate 2 bump_size 5}
>
> I ran your code--using the same 'normal' image that I copied here-- and it seems
> that a gamma of 1.1 that you used is not a good value for a bump_map. I changed
> that value to 2.2 (and boosted the bump_size to 10) and it looks much better.
>
> If I leave out the gamma keyword altogether, the 'flat' result looks nearly
> identical to your 1.1 value. The POV-ray default is 1.0 (i.e., it treats the
> image as 'linear' data.)
>
> Since we are both using jpeg's for the bump_map, they have a standard 'embedded
> gamma' of around 2.2 (or maybe 'srgb'), which is not linear. So using a value of
> 1.1 (or 1.0) changes that; a somewhat simple explanation is that it reduces the
> contrast of the image-as-bump_map.
>
> From the documentation:
> "While POV-Ray will normally interpret the bump map input file as a container of
> linear data [gamma of 1.0] irregardless of file type, this can be overridden for
> any individual bump map input file by specifying gamma immediately after the
> file name."

My sincere apologies. I missed your message. Thank you so much for your help

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