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Author Topic: Understanding Perturbation  (Read 5914 times)
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nitroxis
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« Reply #15 on: September 27, 2014, 02:19:57 PM »

Well, don't ask me tongue stuck out

I for sure want to solve them.
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Kalles Fraktaler
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« Reply #16 on: September 27, 2014, 11:38:17 PM »

Well, you can read the posts about glitch corrections or even examine the source of Kalles Fraktaler. But then you'll just do what we have done.
Maybe you can find a better solution by solving it yourself from scratch with a fresh mind smiley
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Want to create DEEP Mandelbrot fractals 100 times faster than the commercial programs, for FREE? One hour or one minute? Three months or one day? Try Kalles Fraktaler http://www.chillheimer.de/kallesfraktaler
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3dickulus
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« Reply #17 on: September 29, 2014, 11:03:48 PM »

Alright, I got my program working with plain delta iteration. It's able to recognize glitches, however it's not correcting them yet. It currently uses the center of the screen as a reference point. This is not optimal, but I don't really know what to do here. How do I find a relatively good reference point to start with (given the position in the complex plane and a zoom factor)? After the first pass is rendered, do I just use the center of the glitch blobs as new reference point or is there a better way to do this? I don't really understand how SFT is doing it.

Here's what I got so far (red means glitch).
...
The center of a blob is not the best point, you need the locus where the highest iterations are, in the simplest terms one might proceed as follows...

Do a very loose scan, say two or three horizontal and vertical lines through the data rendered from the first pass looking for large blobs
  if found, estimate locus and use as reference point, render pixels marked as glitch, repeat
  if no more big blobs...
Do a more dense scan looking for smaller blobs
  if found, estimate locus and use as reference point, render pixels marked as glitch, repeat
  if no more small blobs...
Do a scan of remaining pixels and use the highest iteration location as a reference, render pixels marked as glitch
  by this time you should be done smiley

Is K.I.Martin's SFT solving glitches at all?
When I ported SFT(java) to C++ I found that the reference point selection wasn't working as well as I though it should and I couldn't quite figure it out so I scrapped the original java version in favor of my own "hunt an peck" method that finally seems to work as of v0.75

 @nitroxis if want to look at the souce  wink

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Resistance is fertile...
You will be illuminated!

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kjknohw
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« Reply #18 on: September 29, 2014, 11:45:20 PM »

The center of a blob works pretty well because it will be close. After a few reference points there is usually no glitch left.
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youhn
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« Reply #19 on: September 30, 2014, 02:57:37 PM »

Not all glitches have roundish shapes, so it does not work well for all glitches. What test locations do you use?
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3dickulus
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« Reply #20 on: October 02, 2014, 01:18:52 AM »

@nitroxis: you got me thinkin' 'bout perturb on GPU

I managed to get par4all working on my linux dev box and here is the result.
p4a did a great job of converting a niffty piece of code, knighty's Pertubation and 3rd degree Mandelbrot evladraw script into working cuda kernels smiley the really cool bit is that it will parallelize loops and such and output code for CUDA, OpenCL, OpenMP, SCMP and a few others. If you can express and idea in linear c99 code this thing can translate it smiley
just a heads up, you can never have too many tools  wink
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Resistance is fertile...
You will be illuminated!

                            #B^] https://en.wikibooks.org/wiki/Fractals/fragmentarium
nitroxis
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« Reply #21 on: October 03, 2014, 03:41:24 AM »

Just a small update...

My program is now able to fix all glitches that occur. It preserves reference points between renders until better points have been found while fixing glitches or the points go out of bounds (i.e. are not in the view rectangle). I am using yet another compute shader to estimate the center of a glitch blob and then recompute all glitched pixels using that point while also adding that point to a list of possible reference points for the next image (useful when you just zoom in and don't pan around too much).

The next thing to work on now is series approximation which I guess will improve performance even more.

Here's a picture of the WIP, the circles show the reference points used to render the image.
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3dickulus
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« Reply #22 on: October 03, 2014, 09:19:06 AM »

Nicely done  A Beer Cup
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Resistance is fertile...
You will be illuminated!

                            #B^] https://en.wikibooks.org/wiki/Fractals/fragmentarium
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