Smoother line optimisations

[funnyboy-roks]

An optimised method of drawing lines was added in #3 that clusters points towards the corners so that there are not large numbers of particles in the center of the lines where they're not necessary and improves the client's ability to render long lines.

I wonder if it would look good to make that a smoother transition, so we have something like

** *  *   *    *     *      *       *        *         *          *          *         *        *       *      *     *    *   *  * **

(although maybe not so linear)