Turns out it can be made quite efficient with a little effort put into arithmetic power reduction. In the outer loop, it is possible to calculate a `dr` value f

Turns out it can be made quite efficient with a little effort put into arithmetic power reduction. In the outer loop, it is possible to calculate a `dr` value from the existing `dx` and `dy`. Then you just increment the radius traveled at the same time as `px` and `py`, and replace the inner loop condition that puts a bound on `z` with a new condition that puts a bound on the radius. That fixes the rotation artifacts, and then makes it really easy to add a distance-based fog effect to hide the cut-off where new terrain comes into view as well.