Ray Gardener schrieb:
> 1. Why is GREY_SCALE3 interpretation being used on 16-bit color data 
> when it isn't on 24-bit data? (source/image.cpp, near line 540). This 
> winds up getting only effective five out of fifteen bits of elevation 
> precision.

I don't know how you come to the 'five out of fifteen bits' but the 
special handling if 24 bit RGB images as 16 bit encoded in red and green 
(see docs for how this works) was an ugly and inefficient hack 
introduced when generic 16 bit formats where not yet common.  This hack 
was not translated to 48 bit RGB - also since it would be rather 
pointless since height values are stored with only 16 bit accuracy 
internally anyway.

> 2. When reading 16-bit grayscale TIFFs, shouldn't the Image->Image_Type 
> field be set to IS16GRAYIMAGE? GeoTIFF elev data can't be used as 
> heightfields correctly without this.

POV-Ray's support for Tiff images is limited to a very small subset due 
to the design of libtiff that only provides higher level functions for 
reading the most basic tiff formats.  I have implemented use of GDAL for 
image reading some time ago (which would offer support for most Tiffs) 
but it is unlikely to make it into an official release version due to 
the optional support of closed formats in GDAL and resulting licensing 
and support issues.  You have to convert such files into a format 
supported by POV-Ray using external tools (Imagemagick, gdal_translate).

-- Christoph

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