In an attempt to write something about that feature, I noticed strange
behaviour of the global_settings number_of_waves parameter.

#include "colors.inc"
camera {location <3,4,3>*4 direction z*2 look_at <0,0,0>}
plane {y,0 pigment {waves color_map {[0 YellowGreen][1 OrangeRed]}}}
global_settings {number_of_waves 12} //default is 10
light_source {<400,500,300> White*1.5 rotate y*50}

This simple scene shows very different results from one compile
to another.  Official POV-Ray works as expected, but any MegaPOV
I tried acts differently (MP7, POVMan, and MLPov), giving different
result from one render to another, sometimes plain color, often
with noticeable plateaus in the waves.

Fabien.

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Oh, I must add that the problem doesn't arise with "ripples".

Fabien.

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Looks to me almost like the pattern type has gone from triangle_wave in
official POV-Ray to ramp_wave in the unofficial POVs.

Bob H.

"Fabien Mosen" <fab### [at] skynetbe> wrote in message
news:3AA16315.FAECF160@skynet.be...
> Oh, I must add that the problem doesn't arise with "ripples".
>
> Fabien.

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In article <3AA16264.309C6534@skynet.be> , Fabien Mosen 
<fab### [at] skynetbe>  wrote:

> In an attempt to write something about that feature, I noticed strange
> behaviour of the global_settings number_of_waves parameter.
>
> #include "colors.inc"
> camera {location <3,4,3>*4 direction z*2 look_at <0,0,0>}
> plane {y,0 pigment {waves color_map {[0 YellowGreen][1 OrangeRed]}}}
> global_settings {number_of_waves 12} //default is 10
> light_source {<400,500,300> White*1.5 rotate y*50}
>
> This simple scene shows very different results from one compile
> to another.  Official POV-Ray works as expected, but any MegaPOV
> I tried acts differently (MP7, POVMan, and MLPov), giving different
> result from one render to another, sometimes plain color, often
> with noticeable plateaus in the waves.

I remember I found a problem with number_of_waves a long time ago.  I am
not sure if the change got into 3.1g or if it is in the current 3.5.  I
can't tell you what MegaPOV does, but I can confirm that there used to
be something wrong with it in the official version.

I think the only workaround is to have the "global_settings" as the very
first thing in a scene.   Alternatively, don't change number_of_waves at
all.


      Thorsten


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

Visit POV-Ray on the web: http://mac.povray.org

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Fabien Mosen wrote in message <3AA16264.309C6534@skynet.be>...
>In an attempt to write something about that feature, I noticed strange
>behaviour of the global_settings number_of_waves parameter.


This is a known bug that is only obvious in versions with a user interface
(Windows and Mac).  What happens is that if you increase number_of_waves,
the number of wave origins is increased, but the program does not update the
list of origins.  As a result, the locations of the additional origins is
undefined.  There is also a second part to this bug:  In versions with a
user interface, when you render a scene, POV-Ray generates the list of wave
origins based on what number_of_waves was set to in the previous rendering,
rather than on its setting in the current scene.

--
Mark

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"Fabien Mosen" <fab### [at] skynetbe> wrote...
> In an attempt to write something about that feature, I noticed strange
> behaviour of the global_settings number_of_waves parameter.
>
[clip]
>
> This simple scene shows very different results from one compile
> to another.  Official POV-Ray works as expected, but any MegaPOV
> I tried acts differently (MP7, POVMan, and MLPov), giving different
> result from one render to another, sometimes plain color, often
> with noticeable plateaus in the waves.

I think the problem is with the waves pattern in general, and not with
number_of_waves.  Even with the default number of waves, you can still see
differences in the pattern.

-Nathan

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