POV-Ray : Newsgroups : povray.general : I think I found the funky hieght field trouble! : Re: I think I found the funky hieght field trouble! Server Time
20 Apr 2024 13:28:45 EDT (-0400)
  Re: I think I found the funky hieght field trouble!  
From: Alain Martel
Date: 27 Mar 2023 15:28:17
Message: <6421ee51$1@news.povray.org>
Le 2023-03-26 à 18:57, William F Pokorny a écrit :
> On 3/26/23 15:36, Leroy wrote:
>> What I'm kind of proud of is that the palette is special. The blue 
>> part of the
>> each palette element matches that element number. So a pigment 
>> function that
>> outputs blue matches the old standard Height field. I didn't plan on 
>> that. When
>> I set it up  all those years ago I did it that way because it was 
>> easier to
>> code.
>>
>> Here One that shows the full 256 range
> 
> Thanks! Played with it a while and yep, these exactly the kind that do 
> work and I've dropped support for them in my povr code... There are many 
> format variations with tga and I thought you might be using something else.
> 
> The tga indexed input POV-Ray allows, can be 8 bit (256 deep) or 16 bit 
> (65535 deep). The latter form won't work correctly with the index method 
> in existing POV-Ray versions. It'll do some sort of wrap.
> 
> I looked around quickly for a converter which would convert to another 
> image format directly from the index values, but had no luck. Something 
> must exist somewhere I'd guess.
> 
> In general our image support is decent, but we don't support everything, 
> every format can do by any stretch. With povr I don't want to burn my 
> limited time on this image support work and I have considered dropping 
> some formats completely. It's just a resource thing. But, I don't know, 
> maybe there is a way to make use of an external conversion library or 
> something.
> 
> Bill P.

Remember that 8 bits and less are paletted formats and that 16 or more 
are non-paletted.
IIRC, in hight fields, when the image is 24 bits, the red and green 
channels are used to to represent the high (green) and low (red) bytes 
of a 16 bits value and the blue channel is ignored.
16 bits is often called high colour and 24 and 32 bit are called true 
colour.


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