Warp schrieb:
>   What kind of color correction do I need when I'm rendering an image to
> be later used to generate a heightfield?
> 
>   The answer is: None.

No, the answer is "that depends on the software reading the heightfield".

 > When I specify a color of 0.5, I expect a value
> which is exactly half of the pixel component value range to be written
> to the image file so that when the image is later used to create a
> heightfield, that pixel will produce a height which is exactly half of
> the maximum height.

What you expect is a color of 0.5 being halfway between 0% height and 
100% height of the height field - and that the absolute vertical 
resolution is independent of the absolute height.

The question, however, is what the software reading the height field 
interprets as 50%:

(a) A brightnes of 50%? (That would appear to me the most "official" way 
to handle PNG files for height fields, and leave you with the option of 
setting File_Gamma any way you like.)

(b) A "framebuffer value" of 127? (That would appear to me the most 
stupid way to handle PNG files for height fields, and leave you with a 
problem indeed.)

(c) An encoded value of 127? (That would appear to me the most 
/reasonable/ way to handle PNG files for height fields, and leave you 
with the option of setting File_Gamma=1.0 to get the desired result, 
even though you might not be aware that it would make a difference.)


Note that in cases (a) and (c) you'd be fine with File_Gamma=1.0, which 
would also ensure a uniform vertical resolution across all heights.

In case (b) however you'd be better off with a different file format, 
because such an encoding would run contrary to the way the PNG file 
format tries to handle gamma.

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