It is possible in MegaPOV, but in the official version you would have to 
use an external program to get the data.

In MegaPOV: Use the trace() function, (assuming your height field is in 
the xz plane), use -y as the direction, and use a point well above the 
height field as the ray starting point. You may want to check the normal 
to see if the height field was really hit, the normal will be < 0, 0, 0> 
if no intersection was found.

It would also be possible to use the hf_height_at() function, but that 
would be a bad idea, because it isn't as versatile and will not be 
supported in the future.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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