In article <3be017fa@news.povray.org> , Warp <war### [at] tagpovrayorg>  wrote:

> :   It seems that now 'evaluate' doesn't actually change the max_gradient, but
> : just calculates the correct one and reports it. The example above renders
> : equally whether or not the 'evaluate' is there.
> :   This behaviour seems logical to me.
>
>   By the way, what is really good about this new behaviour is that now you
> can leave the 'evaluate' after you have fixed the 'max_gradient' to the
> proper value and it will not affect the render (eg. by slowing it).

(This is only relevant for Warp as he has access to code newer than beta 7)

Actually it doesn't matter if you have evaluate in there at all now. As far
as reporting the found maximum gradient is concerned, it now uses some
estimation* as to what can be considered a significant difference and only
(but always) reports the suggested maximum gradient.

The only additional (computational) cost is one floating-point subtraction,
multiplication, division and absolute value in each step of the recursive
root finding process.   It might be that this is still a lot so there might
be need for further changes, or it might turn out that the time impact of
this change is so small that it won't matter too much.

Of course the benefit of removing the need for evaluate all together is that
POV-Ray will now always issue a warning if there is a problem, which in turn
should also reduce problems found by new users who forgot to use evaluate.
While the holes won't go away magically, the warning after rendering will be
a good hint if something is wrong.


    Thorsten


* Absolute differences of +-10 or relative difference of +-10% but not less
than +-0.5 absolute difference will cause the warning.

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

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