Warp <war### [at] tagpovrayorg> wrote:

>   It think there's something odd in the evaluating. I tried with that torus
> and got some strange results.

>   If I, however, specify some max_gradient (eg 2.41) then evaluate in POV3.5
> gives 2.308, which makes more sense. MegaPov gives also a different
> value, in this case 2.312, but still reasonable (although I don't understand
> why it gives a different value).

See  6.5.4.5.3 Maximum Gradient

You should *always* use max_gradient: even for the initial render with
evaluate. If you don't, POV3.5 will *estimate* a starting value which
might be way too high or too low, causing slowdowns and/or inaccuracies.
Use a max_gradient 5 or so to start, together with evaluate 1, 10, 0.99:
this will almost always give a reasonable result.
Then adjust max_gradient and the range of evaluate: a bit less than
found max gradient, a bit more than found max gradient, 0.99
You can even leave evaluate on, since it doesn't slow down the render
(hardly noticable anyway), as long as the max_gradient is accurate and
the evaluate range reasonably accurate.


-- 
e-mail:sme### [at] skynetbe

http://users.skynet.be/smellenbergh

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