The following example of a 3D-fractal animation does not work as expected.

The animation rotates a 3D-fractal around the y-axis. When you render the
animation (25 fps), you will see a 3D-fractal, rotating around the Y-axis,
but additionally you will see an inner move/flow of the fractal itself.
This inner-move makes a jump in speed and direction when you reach a
special position. This happens between frame 535 and frame 536 of an
animation with 4000 frames.
Between frame 535 and 536, the inner-move of the fractal is suddenly
increased
and the direction of the inner-move is reversed. Too see this effect, render
an animation from frame 500 up to frame 560 with a resolution of at least
720x576 with Anti-Alias 0.3 on. (PovRay 3.6.1.c Windows version)

How can I suppress/avoid this strange change in speed and direction of the
inner move/flow of fractal ??

Is there an error in the 3D-fractal calculation ??


Full example:

// Insert in povray.ini
Initial_Frame = 1
Final_Frame = 4000
Cyclic_Animation = on
Subset_Start_Frame= 500
Subset_End_Frame=560



#include "chars.inc"
#include "colors.inc"
#include "textures.inc"
#include "shapes.inc"
#include "shapes2.inc"
#include "shapesq.inc"
#include "stones.inc"
#include "stones1.inc"
#include "stones2.inc"
#include "stars.inc"
#include "skies.inc"
#include "metals.inc"

global_settings {
  number_of_waves 10
  assumed_gamma 1.0
  max_trace_level 10
  adc_bailout 0.006
  max_intersections 80
  photons {
    count 40000
    media 100
    gather 30, 120
    autostop 0
    jitter .4
  }
}

camera{
  location <0, -66,-650> // position of camera <X Y Z>
  sky y
  up <0, 1, 0>           // which way is +up <X Y Z>
  right <-1.77 0.0 0.0>  // which way is +right <X Y Z> and aspect ratio
  look_at <0.0, 0, 0>    // point center of view at this point <X Y Z>
}

light_source{
  <0,-66,-380>
  color rgb 1.5
}

julia_fractal{
  <-0.5664, 0.5106, 0.0224, -0.3024>

  precision 50
  max_iteration 38
  quaternion
  sqr
  hollow on
  texture {
    pigment{
      rgb <1,1.0,1.0>
    }
    finish {
      ambient 0.05
      metallic 0.4
    }
  }

  rotate <-2,19,0>
  rotate <0,0,-10>
  scale <250, 250, 1000>

  rotate<0,90+clock*360*1,0>
}

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Perhaps it's just an aliasing problem? Try increasing the precision
to see what happens.

-- 
                                                          - Warp

Post a reply to this message

"WaveMaster" <nos### [at] yahoocom> wrote:
> The following example of a 3D-fractal animation does not work as expected.
>
> The animation rotates a 3D-fractal around the y-axis. When you render the
> animation (25 fps), you will see a 3D-fractal, rotating around the Y-axis,
> but additionally you will see an inner move/flow of the fractal itself.
> This inner-move makes a jump in speed and direction when you reach a
> special position. This happens between frame 535 and frame 536 of an
> animation with 4000 frames.
> Between frame 535 and 536, the inner-move of the fractal is suddenly
> increased
> and the direction of the inner-move is reversed. Too see this effect, render
> an animation from frame 500 up to frame 560 with a resolution of at least
> 720x576 with Anti-Alias 0.3 on. (PovRay 3.6.1.c Windows version)
>
> How can I suppress/avoid this strange change in speed and direction of the
> inner move/flow of fractal ??
>
> Is there an error in the 3D-fractal calculation ??

Hmm, this might just be nonsense spouting, but my theory is that it's the
Western-movie effect: any chariot/wagon's wheel which moves by more than
half the distance to the next spoke (in a single frame), will look like it
turns in reverse. You are scaling your object more in x than in z, which
means the rotation rate will appear to be non-uniform. If you scaled it in
the same way on all axes the effect might disappear.

Oh, and stones.inc already calls stones1 and stones2, btw.

Post a reply to this message

"WaveMaster" <nos### [at] yahoocom> wrote:
> The following example of a 3D-fractal animation does not work as expected.
>
> The animation rotates a 3D-fractal around the y-axis. When you render the
> animation (25 fps), you will see a 3D-fractal, rotating around the Y-axis,
> but additionally you will see an inner move/flow of the fractal itself.
> This inner-move makes a jump in speed and direction when you reach a
> special position. This happens between frame 535 and frame 536 of an
> animation with 4000 frames.
> Between frame 535 and 536, the inner-move of the fractal is suddenly
> increased
> and the direction of the inner-move is reversed. Too see this effect, render
> an animation from frame 500 up to frame 560 with a resolution of at least
> 720x576 with Anti-Alias 0.3 on. (PovRay 3.6.1.c Windows version)
>
> How can I suppress/avoid this strange change in speed and direction of the
> inner move/flow of fractal ??
>
> Is there an error in the 3D-fractal calculation ??
>
>
> Full example:
>
> // Insert in povray.ini
> Initial_Frame = 1
> Final_Frame = 4000
> Cyclic_Animation = on
> Subset_Start_Frame= 500
> Subset_End_Frame=560
>
>
>
> #include "chars.inc"
> #include "colors.inc"
> #include "textures.inc"
> #include "shapes.inc"
> #include "shapes2.inc"
> #include "shapesq.inc"
> #include "stones.inc"
> #include "stones1.inc"
> #include "stones2.inc"
> #include "stars.inc"
> #include "skies.inc"
> #include "metals.inc"
>
> global_settings {
>   number_of_waves 10
>   assumed_gamma 1.0
>   max_trace_level 10
>   adc_bailout 0.006
>   max_intersections 80
>   photons {
>     count 40000
>     media 100
>     gather 30, 120
>     autostop 0
>     jitter .4
>   }
> }
>
> camera{
>   location <0, -66,-650> // position of camera <X Y Z>
>   sky y
>   up <0, 1, 0>           // which way is +up <X Y Z>
>   right <-1.77 0.0 0.0>  // which way is +right <X Y Z> and aspect ratio
>   look_at <0.0, 0, 0>    // point center of view at this point <X Y Z>
> }
>
> light_source{
>   <0,-66,-380>
>   color rgb 1.5
> }
>
> julia_fractal{
>   <-0.5664, 0.5106, 0.0224, -0.3024>

>   precision 50
>   max_iteration 38
>   quaternion
>   sqr
>   hollow on
>   texture {
>     pigment{
>       rgb <1,1.0,1.0>
>     }
>     finish {
>       ambient 0.05
>       metallic 0.4
>     }
>   }
>
>   rotate <-2,19,0>
>   rotate <0,0,-10>
>   scale <250, 250, 1000>
>
>   rotate<0,90+clock*360*1,0>
> }


To increase the precision does not solve the problem.

I suppose, when the camera position hits the shape of the fractal
(As soon as I am inside the fractal), the calculation of the fractal
data changes and the inner move also.

Why can I not see the Wheel-effect as long as I am outside the shape of
the fractal?? And why does the wheel-effect have an effect on the whole
fractal?
(the inner move/flow changes for the whole fractal)

Post a reply to this message

"WaveMaster" <nos### [at] yahoocom> wrote:

Here you can download the animation of the preceding example (about 4.7
MByte).
It is a short .AVI file, encoded with Windows Media Encoder v9.

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_0505_0550.avi

Post a reply to this message

Here comes an updated, longer version of the preceding animation scene
(6.2 MByte) This animation was rendered with MegaPov 1.21:

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_0500_0560.avi


The next link shows the same scene but exactly 90 degrees later. You can see
the opposite effect as soon as the camera leaves the fractal shape (6.3
MByte):

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_1440_1499.avi


You can also rotate the fractal around the x-axis instead of the y-axis. As
soon as the camera comes near the fractal shape, the inner flow makes an
extream acceleration change.


How can I avoid this or is this an error???

Post a reply to this message

"WaveMaster" <nos### [at] yahoocom> wrote:
> Here comes an updated, longer version of the preceding animation scene
> (6.2 MByte) This animation was rendered with MegaPov 1.21:
>
>
http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_0500_0560.avi
>
>
> The next link shows the same scene but exactly 90 degrees later. You can see
> the opposite effect as soon as the camera leaves the fractal shape (6.3
> MByte):
>
>
http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_1440_1499.avi
>
>
> You can also rotate the fractal around the x-axis instead of the y-axis. As
> soon as the camera comes near the fractal shape, the inner flow makes an
> extream acceleration change.
>
>
> How can I avoid this or is this an error???

I think it's still the wheel effect. If you make a wheel animation and let
its velocity vary, you'll see it alterning between clockwise and
counter-clockwise rotation, even though it's "really" only going in one
direction in the code. Likewise, in your scene, angular velocity varies a
lot when you try to go in the fractal, as opposed to the fairly smooth
movement in the beginning of the animation.
That's my guess, anyway.

You may find you'd get more feedback if you used non-Windows specific
codecs, Xvid or Mpeg should be supported on a fair number of platforms.

Post a reply to this message

> You may find you'd get more feedback if you used non-Windows specific
> codecs, Xvid or Mpeg should be supported on a fair number of platforms.

As wished here comes the MPEG2 version of the preceding downloadlinks:

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_0500_0560.mpg
http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_01_MegaP_1440_1499.mpg

both files are about 2.3 MByte

Post a reply to this message

I did a new rendering with a new scene-file. The following changes have been
made:

camera{
  location <0, 0,-650>   // position of camera <X Y Z>
  sky y
  up <0, 1, 0>           // which way is +up <X Y Z>
  right <-1.77 0.0 0.0>  // which way is +right <X Y Z> and aspect ratio
  look_at <0.0, 0, 0>    // point center of view at this point <X Y Z>
}

light_source{
  <0, 0,-380>
  color rgb 1.8
}

julia_fractal{
  <-0.5664, 0.5106, 0.0224, -0.3024>
  slice <0,0.43,0,1.0>, 0.0
  precision 50
  max_iteration 38
  quaternion
  sqr
  hollow on
  texture {
    pigment{
      rgb <1,1.0,1.0>     // White
    }
    finish {
      ambient 0.09
      metallic 0.4
    }
  }
  rotate <-2,19,0>
  rotate <0,0,-10>
  scale <250, 250, 1000>

  rotate<0,90+clock*360*1,0>
  translate <0, 135, 0>
}
julia_fractal{
  <-0.5664, 0.5106, 0.0224, -0.3024>
  slice <0,0.43,0,1.0>, 0.0
  precision 50
  max_iteration 38
  quaternion
  sqr
  hollow on
  texture {
    pigment{
      rgb <0.5,1.0,0.5>  // Green
    }
    finish {
      ambient 0.09
      metallic 0.4
    }
  }

  rotate <-2,19,0>
  rotate <0,0,-10>
  scale <250, 250, 900>

  rotate<0,90+clock*360*1,0>
  translate <0, -135, 0>
}

Download link:

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_04_MegaP_0530_0599.m2v



Afterwards I rendered the following scene-file:

julia_fractal{
  <-0.5664, 0.5106, 0.0224, -0.3024>
  slice <0,0.43,0,1.0>, 0.0
  precision 50
  max_iteration 38
  quaternion
  sqr
  hollow on
  texture {
    pigment{
      rgb <1,1.0,1.0>   // White
    }
    finish {
      ambient 0.09
      metallic 0.4
    }
  }

  rotate <-2,19,0>
  rotate <0,0,-10>
  scale <250, 250, 1000>

  rotate<0,90+clock*360*1,0>
  translate <0, -135, 0>
}
julia_fractal{
  <-0.5664, 0.5106, 0.0224, -0.3024>
  slice <0,0.43,0,1.0>, 0.0
  precision 50
  max_iteration 38
  quaternion
  sqr
  hollow on
  texture {
    pigment{
      rgb <0.5,1.0,0.5>     // Green
    }
    finish {
      ambient 0.09
      metallic 0.4
    }
  }

  rotate <-2,19,0>
  rotate <0,0,-10>
  scale <250, 250, 900>

  rotate<0,90+clock*360*1,0>
  translate <0, 135, 0>
}

Download Link:

http://homepage.sunrise.ch/mysunrise/go_huerlimann/PovRay/FractalTest_04b_MegaP_0530_0599.m2v



Facts:

The white fractal has a z-scale by 1000, the new green fractal has a z-scale
by 900. The rest stays identical. Both fractals have a symmetrical
y-translation by +/-135 units.

If the inner move is made by the "wheel effect", then both fractals should
change the inner move on different positions/in different directions. But
as you can see, the inner move changes at the same position in both
fractals.

The second example exchanges only the two fractals in the y-direction. And
again, both fractals change the inner move at the same position!!

Question:

Can this facts be explained by the wheel effect??
For me, there is an error in the fractal calculation!!

Post a reply to this message

"WaveMaster" <nos### [at] yahoocom> wrote:
> Facts:
>
> The white fractal has a z-scale by 1000, the new green fractal has a z-scale
> by 900. The rest stays identical. Both fractals have a symmetrical
> y-translation by +/-135 units.
>
> If the inner move is made by the "wheel effect", then both fractals should
> change the inner move on different positions/in different directions. But
> as you can see, the inner move changes at the same position in both
> fractals.
>
> The second example exchanges only the two fractals in the y-direction. And
> again, both fractals change the inner move at the same position!!
>
> Question:
>
> Can this facts be explained by the wheel effect??
> For me, there is an error in the fractal calculation!!

I'm not sure it proves anything, actually. Could there be a bug in how
POV-ray handles Julias? Certainly! It wouldn't be the first time. You are
saying that two wheels, one smaller and one bigger but with spokes at the
same relative angles, wouldn't display the same "wheel effect" as their
rotation speed increased. But the wheel effect is determined by the angular
velocity of the rotation: in your scene that is determined solely by the
rotation of the clock, as angular velocity is independent of radius.
Consequently both scenes display the same behaviour.
I believe that in order to overcome the problem you need to have smaller
steps the closer you get to the fractal. Unfortunately there is no "fixed
step" rotation that can avoid the effect, AFAIK.

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