Am 15.02.2016 um 16:05 schrieb Kenneth:

> (I actually used assumed_gamma 2.0 for my tests, in v3.62, but you should use
> 1.0 for yours, in v3.7. The color will look somewhat different.)

Speaking of gamma...

> #declare Fn_1 = function
> {
>  pigment
>  {
>   image_map {
>    jpeg "colony ship i - heightfield landscape 1000px.jpg" once interpolate 2 }

... you should add "gamma 1.0" after the filename (or whatever your
assumed_gamma setting is).


When used in an image_map, POV-Ray by default assumes that the image
uses gamma encoding (which most people think is linear but actually
isn't), and needs to be converted to POV-Ray's truly linear colour space
upon loading (presuming assumed_gamma is 1.0).

However, when an image is used to represent terrain height rather than
colours, the usual approach is to encode terrain height in a truly
linear fashion. If you use an image in a height_field, POV-Ray takes
this into account, and performs no gamma adjustment on the image data
whatsoever (unless you explicitly tell it otherwise).

With a HF_Cylinder, POV-Ray cannot do this automatically, because it has
no way of knowing that the colours in the image_map will ultimately be
converted into height values. Therefore, by default it /will/ perform
gamma adjustment.

Specifying "gamma 1.0" after the filename tells POV-Ray that the image
data is encoded linearly, so if "assumed_gamma" is also set to 1.0
POV-Ray's gamma adjustment for that particular image is a 1:1 mapping,
effectively leaving the data unchanged.

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