Draw circle algorithmically with surface object

[keokeo]

In the file posted below there is a simple test of Bresenham's circle algorithm used with the surface object.

View MFA

However it's doesn't work well and instead of a cirlce it draws a rhombus-looking shape. The problem seems to be in how I have implemented the if-else part. I tried doing some kind of nested loop but it didn't work well either. Anyone know how to do this part correctly?

I used the algorithm as it is presented here:
http://www.eazynotes.com/notes/computer-graphics/algorithms/bresenham-circle-algorithm.pdf

[Looki]

There are 2 errors in your code.

The first error is as you stated the 'else' part - in the first On loop "if" condition, you alter the D variable and then compare to its value later, which is wrong. You need a switch variable for that.

The other area is that you use the wrong formula in the second action... use D( "Surface" )+4*(Xd( "Surface" )-Yd( "Surface" ))+10

[keokeo]

That's so beautiful, the absolute perfection of math. Thanks Looki.