[PD] Graph a circle arc in an array?

[Peter Brinkmann]

On Sat, Apr 9, 2011 at 7:32 PM, Mathieu Bouchard <matju at artengine.ca> wrote:

> On Sat, 9 Apr 2011, Peter Brinkmann wrote:
>
>  By the way, there's a way to draw a circle using nothing but addition:
>> http://en.wikipedia.org/wiki/Midpoint_circle_algorithm
>> Implementing this in Pd is completely impractical, but it's fun to think
>> about.
>>
>
> It's not strictly the same thing, because by using sin and cos, you are
> ensuring equal distance between points at infinite resolution, and you are
> ensuring equal angles everywhere too.
>
> With the midpoint circle algorithm, instead, you are ensuring that all
> points are one pixel apart, when using a limited resolution. The pixels are
> considered one pixel apart when sharing an edge or corner. This is related
> to http://en.wikipedia.org/wiki/Maximum_norm
>
> So, it depends on whether you're trying to draw something
> continuous-looking on a pixel display.


Sure, but in this case the goal was to draw a section of a circle in an
array, and the midpoint algorithm would be a good choice if implementing it
in Pd weren't so complex.  Anyway, it doesn't really matter, I just like
Bresenham-style algorithms.
Cheers,
     Peter
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