In article <t62tsu4m6eq18omqjunq22lug2aji9a3pp@4ax.com>,
 Peter Popov <pet### [at] vipbg> wrote:

> >Actually, a dark opaque pigment makes sense here, you usually can't see 
> >through this kind of water unless you are right above a shallow portion, 
> >and the scene is already slow rendering. 
> 
> Attenuation won't slow it down, but it adds more realism along the
> shores and at steep angles of incidence.

Instead of an opaque texture? Yes, it will be slower. The attenuation 
calculations themselves don't cost much, though they are quite a bit 
more than just using a constant color value, but any transparency at all 
will require tracing at least one refracted ray every time the water is 
hit, and then the additional texture calculation of the ground under the 
water.

The shores often don't slope gradually out of the water, in fact there 
is often an overhang. It takes practice to see into the water in this 
situation even when it is clear, and if the water is carrying lots of 
silt, you often can't see your feet if you are wading. A nearly black 
opaque texture is a decent time saving approximation for this type of 
image, even if it won't look good close up.

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

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