In article <3ee29c31$1@news.povray.org>,
 Lutz-Peter Hooge <lpv### [at] gmxde> wrote:

> -Are 16bit TIFFs not supported in height_field?

Probably not. From memory, POV supports 16-bit PNG grayscale, POT (some 
odd kind of 16-bit GIF), and a little hack where it uses the red and 
green channels of an RGB TGA file to store a 16-bit gray value.


> It does work (no error), but the result looks like 8bit.
> When I convert the TIFF to PNG first, it looks much smoother.
> The TIFF was generated by Picture Publisher 10.
> It this an issue with TIFFs in general, or only with TIFFs generated
> by Picture Publisher?

Maybe neither. There've been problems with TIFF support before, it is 
apparently quite common for software to not support it fully, and POV 
does not mention it in the section on 16-bit formats.


> -Is there a version of POV-Ray that supports more than 8bit/channel
> in pigments, so that it is possible to make an iso-heightfield from
> an 16bit grayscale image? (function{pigment{image_map{...}}})

Color math in POV is done as single precision floating point. The 8/16 
bit limitation is internal to the file formats, not to POV.


> I tried MLPov with an hdr image (converted with HCRedit), but still
> the result didn't look as smooth as the 16bit PNG heightfield.
> Maybe MLPov converts it back to 8bit when it is used inside a function?

I'm not sure how HDR images store the values, they may just not have the 
precision you are expecting. They cover a wider dynamic range, and small 
levels are useless in much of that range, so to save memory it may 
distribute the levels more densely at the lower intensities. I'm not 
sure what you're trying to do using them for a height field or 
isosurface, if you want more precision you should just use a 16 bit 
image. (And why compare a HDR isosurface to a PNG height field?) One 
more thing: make sure you have bilinear interpolation turned on, the 
isosurface solving algorithm doesn't deal well with the infinite 
gradients between solid pixels.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

Post a reply to this message