Polar to cartesian and back by Nebukadnezar

Polar to cartesian and back by Nebukadnezar
http://filterforge.com/filters/10577.html

Thanks! For some reason, I can't download this filter, but the link in my filter comments works.

Thx, guys!

Indigo, I updated it yesterday, because I had mixed up the description of the controls.
Might be that caused your problem.

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Morgantao wrote: Looks great. Makes me wish I had a clue, so I could use it

Well, I really have been looking at it, and really the same as you I do not have a clue how to use this inside a filter.

This filter has been done after the Indigo Ray request here

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Indigo Ray wrote: You can see why I didn't include this feature in the submitted filter. Anyone want to figure out POLAR → CARTESIAN transform with free gradients?

Although I do not know how to use this inside a filter it STILL IS A USEFUL FILTER

You can create weird distorsions

Here is a close up of a tulip flower through this filter

one more

Can convert a circular shape into a linear shape AND linear shapes into curves (you can see how the white frame has been converted )

And this are horizontal stripes

And what happens if you want to make a big Niagara style waterfall from a city skyline?, well here is one example of an aerial syline of New York converted with this filter into a waterfall

I know how to use this inside a filter, but my problem is when I go from cartasian to polar, lines get wider and wider as they move further away from the center.
I need to figure out a way to distort thing BEFORE they enter the cartasian to polar... And other stuff after that

I also wanted to see what happens when you transform a Polar (bear ) to cartesian

As for your other examples, they surely look nice and I won't stop you, but there are other filters around that can do that with more options available.

The intended purpose of this filter is really just the single case, where you already have a radial image and want to apply an horizontal or vertical effect. (Better vertical, since the proportions get distorted horizontally, as Morgantao points out. But you are free to toy around with it, of course, and use it to your advantage. Adding a horizontal skew for example will add a spiraling effect, like SpaceRays example for posts above this shows, if you read it from right to left.)
If you then put the image with the parallel effect back to polar coordinates, you will have a radial effect. Which will necessarily taper, since what was the whole width of the image will converge to a single point. If you want evenly thick edges you could perhaps apply an edge detection or high pass on filled forms.

So obviously that transformation should happen as lossless as possible, without loosing any part of the image. In fact I suspect FF will not touch the parts of the image that weren't changed during the conversion at all, because it figures out that the transformations of the conversion cancel each other out.


@Morgantao: There is actually a filter by ThreeDee in the library, called "Radial Spokes". It might do what you are looking for. Basically what it does is taking a spoke at the vertical center of the image, how it is supposed to look later, transforms that to cartesian and gets the distorted shape you are looking for.

I guess they had no Lookup back then or free/radial gradients, so a lot of that can be simplified.
Just feed your single spoke into the leftmost Lookup of my Snippet, tile/offset that to the number you require and put it into the right Lookup. Be aware that it will be cropped a bit, though.

Cool snippet, not sure where I'll use it yet but thanks.