Reading this link

http://news.povray.org/povray.binaries.images/thread/%3Cweb.45dbe0082f42fd2caa2e049f0%40news.povray.org%3E/

And remember similar problems I have in proper experience

I think, only for a few points we need rendering entire image at slow speed
rate (ie applying higher max_trace_level or some other stuffs)

I suggest a small mod for POV, wend rendering a image with multi
frame_number, give the possibility of keep the pixels of the prior
frame_number, and rendering only the pixels with "zero render" (black dots)
in the new frame, this it makes possible to make images with multipass
render.

Activate this feature with a "+multipass" switch or so combined with
animations swiches, but the target is a static frame, not animation, we
reuse the animations routines for multipassing

example:

#if (frame_number=0) // first fast pass
  global_settings {
    max_trace_levels 5 // fast render with many black areas
  }
#end
#if (frame_number=1) // second pass
  global_settings {
    max_trace_levels 50 // render with some black dots
  }
#end
#if (frame_number=2) // final render
  global_settings {
    max_trace_levels 500 // slow render without black dots
  }
#end

....


The idea is save render time calculating a high percentage of the image at
"low trace rate", then recalculate the rays at more trace level for pixels
undefined in prior pass.

Sorry for my english

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"Agustin Britait Molina" <agu### [at] hotmailcom> wrote:
> I suggest a small mod for POV, wend rendering a image with multi
> frame_number, give the possibility of keep the pixels of the prior
> frame_number, and rendering only the pixels with "zero render" (black dots)
> in the new frame, this it makes possible to make images with multipass
> render.
>
> Activate this feature with a "+multipass" switch or so combined with
> animations swiches, but the target is a static frame, not animation, we
> reuse the animations routines for multipassing
>
> ....
>
>
> The idea is save render time calculating a high percentage of the image at
> "low trace rate", then recalculate the rays at more trace level for pixels
> undefined in prior pass.
>
> Sorry for my english

Perhaps I'm mistaken in the way max_trace_level works or what you are
proposing, but I don't know if this would be effective.  Max_trace_level is
just a way of specifying a maximum number of refractions/reflections per ray
to limit infite (or too large number) of refraction/reflection.  Howver,
this is an upper bound and is only used if needed.  If a ray terminates
before max is reached, it terminates, no further level is needed or used.
Essentially it already does what I understand you are suggesting.  For
example, try the following scene:

//START
global_settings {
  ambient_light 1
  max_trace_level 250 //2
}

camera{
  up y*image_height
  right x*image_width
  angle 60
  location <0,0,-100>
  look_at  0
}

light_source{y*500 rgb 1}

sphere{-y*10,20 pigment{rgb 1}}

box{-600,600
  texture{
    pigment{rgb 0}
    finish{reflection{0}}//1
  }
}
//END

Essentially just a sphere inside a perfectly mirrored (or not) box.  When
setting "reflection 0", max_trace_level has virtually no effect on the
render speed, there are no reflections so, even if you have a very high
level set, it is not needed and ignored.  Setting "reflection 1",
max_trace_level has a great effect, as it now has to determine when to
terminate the ray, otherwise it would go off to infinity.

Hope this helps if I understand your intention correctly.

-tgq

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Agustin Britait Molina wrote:
> Activate this feature with a "+multipass" switch or so combined with
> animations swiches, but the target is a static frame, not animation, we
> reuse the animations routines for multipassing

This is the wrong group for a feature suggestion.  This group is for
discussion of the POV-Ray source code, not general feature suggestions for
POV-Ray.  Feature suggestions for POV-Ray should be made in either
povray.general or povray.newusers.

	Thorsten, POV-Team

Post a reply to this message

"Trevor G Quayle" <Tin### [at] hotmailcom> wrote:
> Perhaps I'm mistaken in the way max_trace_level works or what you are
> proposing, but I don't know if this would be effective.  Max_trace_level is
> just a way of specifying a maximum number of refractions/reflections per ray
> to limit infite (or too large number) of refraction/reflection.  Howver,
> this is an upper bound and is only used if needed.  If a ray terminates
> before max is reached, it terminates, no further level is needed or used.
> Essentially it already does what I understand you are suggesting.
> -tgq

max_trace_levels not only works on mirrors, I understand ur example, but in
some cases, a high trace level slow the render, and the difference in final
result with high/low trace levels are minimal, some error dots, eliminate
these dots need great ammount of time render, could save it with some
multipass options

Please take a view to this topic:
http://news.povray.org/povray.binaries.images/thread/%3Cweb.45dbe0082f42fd2caa2e049f0%40news.povray.org%3E/

The final result surely differs of a full slow render in one pass, but the
saved time make this aceptable.

In other side, max_trace_level are not the only parameter susceptible to
change... cameras, we can add a set of clip&offset options to make a render
of multiples images in a unique image, like a four-view template of a model
(top-side-front-perspective views), maybe a two-view of a model
before/after applying a change, multipass have many aplications

Post a reply to this message

Agustin Britait Molina wrote:
> I think, only for a few points we need rendering entire image at slow speed
> rate (ie applying higher max_trace_level or some other stuffs)

Why not just re-render with a bounding box, and paste the new rectangle 
into the final image?


-- 
   Darren New / San Diego, CA, USA (PST)
    "I'm getting addicted to feet. Which is
     bad, because they're like $5 a pound."

Post a reply to this message

Thorsten Froehlich <tho### [at] trfde> wrote:
> This is the wrong group for a feature suggestion.  This group is for
> discussion of the POV-Ray source code, not general feature suggestions for
> POV-Ray.  Feature suggestions for POV-Ray should be made in either
> povray.general or povray.newusers.
>
>  Thorsten, POV-Team

ups, sorry

Darren New <dne### [at] sanrrcom> wrote:
> Why not just re-render with a bounding box, and paste the new rectangle
> into the final image?
>

???

I find on internet, but "bounding box" are too generalist term

what are a bounding box?

Post a reply to this message

Agustin Britait Molina <agu### [at] hotmailcom> wrote:
> The idea is save render time calculating a high percentage of the image at
> "low trace rate", then recalculate the rays at more trace level for pixels
> undefined in prior pass.

  I think that what you are looking for is this:

http://povray.org/documentation/view/3.6.1/258/

-- 
                                                          - Warp

Post a reply to this message

Agustin Britait Molina wrote:
> Please take a view to this topic:
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.45dbe0082f42fd2caa2e049f0%40news.povray.org%3E/

Sadly the advice about max_trace_level in that thread (by two other users)
was plain wrong :-(

	Thorsten, POV-Team

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