I'm setting up an animation, where every frame is very different.  I only want
povray to go to the trouble of creating an image if condition  #if() is met.
Are there certain kinds of errors for which povray will give an error so
serious it refuses to create an image, but go on to the next frame?  Something
like 1/0?  And in these cases, does it always create an all-black bitmap?

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"gregjohn" <pte### [at] yahoocom> wrote in message 
news:web.48aea49b13c48d0e34d207310@news.povray.org...
> I'm setting up an animation, where every frame is very different.  I only 
> want
> povray to go to the trouble of creating an image if condition  #if() is 
> met.
> Are there certain kinds of errors for which povray will give an error so
> serious it refuses to create an image, but go on to the next frame? 
> Something
> like 1/0?  And in these cases, does it always create an all-black bitmap?

I believe that any error serious enough to actually prevent POV-Ray from 
creating one image in an animation sequence will halt the render and prevent 
it from generating subsequent images in the sequence.

There are certain things that will produce an all-black image, such as not 
having anything in the scene (which can render very quickly).

I'm not sure about exactly the problem you're trying to solve, but if you 
have a big list of images and you want to suppress certain ones based on 
something that's evaluated only when you generate the sequence, you could 
always use the POV-Ray write command to generate a list of the ones you need 
to delete in a format that you can run as a script once the renderer has 
finished.

Regards,
Chris B

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"Chris B" <nom### [at] nomailcom> wrote:
> There are certain things that will produce an all-black image, such as not
> having anything in the scene (which can render very quickly).

Ironically, this sentence gives me the advice I needed.  The problem is that the
set of images which I wished to ignore were also the ones that rendered
extremely slowly. And my #if() predicts the render speed.  I could simply put a
black object in front of the camera when #if() is meet, and meet at least half
of my objectives.

thanks.

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gregjohn <pte### [at] yahoocom> wrote:
> Ironically, this sentence gives me the advice I needed.  The problem is that the
> set of images which I wished to ignore were also the ones that rendered
> extremely slowly. And my #if() predicts the render speed.  I could simply put a
> black object in front of the camera when #if() is meet, and meet at least half
> of my objectives.

  Wouldn't it be much easier to do this:

#if(condition)
  #include "TheActualSceneFile.pov"
#end

  Then render this scene instead of TheActualSceneFile.pov.

-- 
                                                          - Warp

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"gregjohn" <pte### [at] yahoocom> wrote:
> I'm setting up an animation, where every frame is very different.  I only want
> povray to go to the trouble of creating an image if condition  #if() is met.
> Are there certain kinds of errors for which povray will give an error so
> serious it refuses to create an image, but go on to the next frame?  Something
> like 1/0?  And in these cases, does it always create an all-black bitmap?


if every frame is very different, why not use a case/switch based on the
frame_number?  That or set your clock variable in such a way that every frame
can be used - depending on the length of the animation, processing frames that
aren't needed may add an unnecessarily large amount of time.

Something like:


#switch( frame_number )

    #case( 4 ) // object for frame four:
        box{ <-1,-1,-1>, <1,1,1> }
        ...
    #break

    #range( 1, 5 ) // objects for frames 1 through 5
        // note that all clauses that are true will be processed
        sphere{ }
        ...
    #break
#end



Either that, or use the file queue and set up several files in advance, perhaps
in conjunction with the above techniques

-Reactor

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

> Wouldn't it be much easier to do this:
>
> #if(condition)
>   #include "TheActualSceneFile.pov"
> #end
>
>

I'm randomly exploring fractal space, and only want images if they are
interesting based on the condition in #if().  But maybe the best way in all of
this is a while loop that goes back to find another random location in the
pattern if the chosen location isn't interesting enough.

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gregjohn nous illumina en ce 2008-08-22 23:11 -->
> Warp <war### [at] tagpovrayorg> wrote:
> 
>> Wouldn't it be much easier to do this:
>>
>> #if(condition)
>>   #include "TheActualSceneFile.pov"
>> #end
>>
>>
> 
> I'm randomly exploring fractal space, and only want images if they are
> interesting based on the condition in #if().  But maybe the best way in all of
> this is a while loop that goes back to find another random location in the
> pattern if the chosen location isn't interesting enough.
> 
> 
> 
When randomly exploring a fractal, it's very hard to detect if a given 
"location" is interesting before you actualy render that location. Your test may 
flag a marvalous location as uninteresting and skip it, and then render 100 of 
extremely boring ones accidentaly flaged as "interesting"...

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you tell stories to your kids that 
include stuff like "Once there was a polygon mesh who was very sad because he 
was only Gourard shaded."
     -- Taps a.k.a. Tapio Vocadlo

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Alain <ele### [at] netscapenet> wrote:

> >
> When randomly exploring a fractal, it's very hard to detect
> if a given "location" is interesting before you actualy
> render that location. Your test may flag a marvalous
> location as uninteresting and skip it, and then render 100 of
> extremely boring ones accidentaly flaged as "interesting"...
>

No, with eval_pigment, one may compare the colors of two close-by points in
fractal space.  If they are identical, then there's a good chance you're out in
a field of blanket color.  I had a pretty good run of looking at fields where
the colors were dissimilar. Not all worthy of uploading to zazzle, but
certainly interesting.    I think the most interesting test (but biggest
longshot as far as remote odds) would be to look for a black spot and a
non-black spot in the same field.

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gregjohn nous illumina en ce 2008-08-25 22:28 -->
> Alain <ele### [at] netscapenet> wrote:
> 
>> When randomly exploring a fractal, it's very hard to detect
>> if a given "location" is interesting before you actualy
>> render that location. Your test may flag a marvalous
>> location as uninteresting and skip it, and then render 100 of
>> extremely boring ones accidentaly flaged as "interesting"...
>>
> 
> No, with eval_pigment, one may compare the colors of two close-by points in
> fractal space.  If they are identical, then there's a good chance you're out in
> a field of blanket color.  I had a pretty good run of looking at fields where
> the colors were dissimilar. Not all worthy of uploading to zazzle, but
> certainly interesting.    I think the most interesting test (but biggest
> longshot as far as remote odds) would be to look for a black spot and a
> non-black spot in the same field.
> 
> 
You'll need to sample 100's of pairs to be sure. If you sample only 2 locations, 
you may well miss a very interesting image. Two close-by points can be 
identical, and be just next to some very busy area, or just apen to lie 
parallel, or almost, to the local gradient.
You need a bare minimum of 3 points in a triangle.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you look at real clouds and 
criticise their media and radiosity settings.
Tom Melly

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Alain <ele### [at] netscapenet> wrote:

> You'll need to sample 100's of pairs to be sure. If you sample
> only 2 locations, you may well miss a very interesting image.
> Two close-by points can be identical, and be just next to some
> very busy area, or just apen to lie parallel, or almost, to
> the local gradient.
> You need a bare minimum of 3 points in a triangle.
>


How about a #while loop set to kick out when it reaches 9999?  It's just a
computer doing the heavy lifting, it doesn't get bored!  ;-)

I tried a three-pointer for a while but wasn't sure I liked the results better.

I'm still learning the geography of the Mandelbrot set, but I ended up in too
many places where it was uber-busy, unartistically so.

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