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Author Topic: backwards compatibility  (Read 241 times)
Description: maintaining appearance
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claude
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« on: September 14, 2017, 08:14:25 PM »

It was brought to my attention that the Distance colouring method has always looked different in my GMP fork compared to the last upstream binary version 2.11.1.

I managed to track this down to the very early history of my fork, when I imported the contents of the 2.11.1 source code zip.

Turns out the source code doesn't quite correspond exactly to the released binary version - it has an extra square root in the Distance function (and possibly other changes). sad

So my plan of action to resolve this mess and make old parameter files look correct in my fork:

* make ColorMethod 5 correspond to Distance (Linear) for compatibility with 2.11.1 upstream binary version (it was (Distance (Square Root) in my fork, until now, apart from one version)
* make ColorMethod 7 correspond to Distance (Logarithm) for compatibility with my fork version (anyway a new feature in my fork compared to upstream binary)
* add a ColorMethod 8 corresponding to Distance (Square Root) for compatibility with my fork version

Therefore some settings made with my fork will have to be changed manually, ie change ColorMethod 5 Distance to ColorMethod 8 Distance (Square Root) (or ColorMethod 7 Distance (Logarithm) for that one GMP fork version with log transfer in the de function)

Any comments?  This is a bit of a mess all around...

EDIT Here are some test images:

2.9.4 upstream


2.9.11 upstream


linear


logarithm


square root


So it isn't just linear scaling that is the issue, there's some other missing ingredient, and older versions differ between themselves too (but not as much).

What to do? sad
« Last Edit: September 14, 2017, 09:59:16 PM by claude, Reason: pics » Logged
Adam Majewski
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« Reply #1 on: September 14, 2017, 10:35:29 PM »

Standard description ( mini help) in main.cpp file line 256 is:

Available color methods are
* Standard: Standard iteration band coloring
* Square root: Iterations are squared before colors are appplied
* Cubic root: Cube root is applied before colors
* Logarithm: Logarithm is applied before colors
* Stretched: The palette is stretched over min-max iteration values
* Distance: Distance Estimation


https://en.wikibooks.org/wiki/Fractals/kallesfraktaler#coloring_methods
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Kalles Fraktaler
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« Reply #2 on: September 15, 2017, 12:12:09 PM »

Hi

I like logarithm best, it corresponds to what I was trying to achieve.
Sqrt could achieve the same result, but the palette need to have larger and larger areas of the same color.

As shown by your examples, it requires a good AA to make DE look good.
Claude did your program also require a big AA for DE?

Histogram would be a nice to have, even though I never got into it as much as I was able to implement it smiley
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