From: Clifford Heath <no@...>
Date: 2008-01-17T07:40:05+09:00
Subject: Re: spatial search & search radius circumference with Geokit

Xin Zheng wrote:
> Are you using the same algorithm?
> Are you using the same circumference?

The algorithm using 360 degrees of sin and cos is
the most naive and inefficient one possible. Look
up Bresenham's algorithm for circles, and run it
for 1/8 of the circumference, using reflection and
rotation for the rest.

It's well known that Bresenham's works for straight
lines, but there's a cute version that does circles
and ellipses also, using pure integer arithmetic
and no multiplication or division.

Google finds plenty of presentations showing how.