Help with circle

[Carlo Valpiani]

Hi,

Embarking on the learn how to program the -1 I thought I'd start with a small hack of the circle program. Using the algorithm at 

https://nbickford.wordpress.com/2011/04/03/the-minsky-circle-algorithm/ 

I modified the circle program in tapes to use DIV instead of SAR instructions and have been able to create horizontal and vertical ellipses. I haven't been to draw ellipses at 45 degree angles, the best I could do is in the picture. Does anybody know the initial values to plug in to draw the oblique ellipses or is it not possible with the -1 integer arithmetic?

Thanks

Carlo

[Bill E]

I don't know any reason offhand why it wouldn't work, but if you share the code, I'll take a look.

Bill 

[Norbert Landsteiner]

The 45 degree rotation is a feature of the basic algorithm, actually a spatial "drift" or displacement in the approximation.

You can find a closer discussion of this at https://www.masswerk.at/nowgobang/2023/minskytron (unfinished draft). Mind the note in the blue box.

– Norbert

[Carlo Valpiani]

Thanks for all the suggestions.

I tried various combinations using Bill's ad1 but couldn't create a narrow ellipse at 45 degrees, as the ellipses narrow they tend to either horizontal or vertical. I think it is a limitation of the integer arithmetic.

Carlo

[Carlo Valpiani]

I found an integer transpose and rotate algorithm at www.geometrictools.com and implemented the rotate part on circle.rim. It does what I wanted to do. A demo program is attached. Uses test word to configure. How to use documentation is in the source. It assumes am1 and Bill's pidp1-mods implementation.

Carlo