Andy W nous apporta ses lumieres en ce 2007/11/24 06:54:
> Hello. I'm new to POV-ray and new to these groups. I'm trying to use POV to
> create nice photo-real earth imagery (or exaggerated earth imagery, boosting up
> the terrain).
> 
> To try and do this I've got satellite imagery, which I can drape over
> height-field topography. This looks fine using some 8 bit topography entered as
> height-field.
> 
> But when I try and bring in 16-bit imagery I can't seem to get it to work. It
> clearly doesn't support 16-bit GeoTIFF, so I've tried converting from GeoTIFF
> (and from raw) using Image-Magick to get one of the 16 bit formats supported by
> POV. I've created 16 bit PGM, and 16 bit PNG (as well as all sorts of odd
> formats with 16-bit red channel and nothing green or blue), but these don't
> seem to create what I want.
> 
> It looks like they are overflowing at the value 256, and are not really 16 bit.
> Or there's a little-endian/big-endian confusion, but switching between the two
> doesn't help.
> 
> Is there something special in the 16 bit formats used by POV? Are they signed or
> unsigned? And can anyone recommend a way of creating usable 16 height-fields
> from raw or geotiff files [I'm exporting these from Global Mapper if anyone is
> familiar]? What options would be sensible on an image magick command line to
> create these?
> 
> For your information, I'm working under Windows XP, and at the moment don't have
> any compilers for a recompilation as I'm scared of compiling anything under Win
> because it's such a stupid system.
> 
> Thanks in advance if anyone can help me.
> 
> 
Try the TGA or PPM format. High byte in the red channel, low byte in the green 
channel, blue set to zero.
This is the format used when you set hf_gray_16 in global settings and the 
output as TGA.

You may also use 16 bits PNG and POT file.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when your wife's raytraced image you 
made to flatter her is the only one you see of her anymore.
Ken Tyler

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