Function rectangularSpiral

docs/app/js/sanddance-app.js:140978–141001

(size)

    };
}
function rectangularSpiral(size) {
    var dy = 4, dx = dy * size[0] / size[1], x = 0, y = 0;
    return function(t) {
        var sign = t < 0 ? -1 : 1; // See triangular numbers: T_n = n * (n + 1) / 2.
        switch(Math.sqrt(1 + 4 * sign * t) - sign & 3){
            case 0:
                x += dx;
                break;
            case 1:
                y += dy;
                break;
            case 2:
                x -= dx;
                break;
            default:
                y -= dy;
                break;
        }
        return [
            x,
            y
        ];
    };
} // TODO reuse arrays?
function zeroArray(n) {
    var a = [], i = -1;
    while(++i < n)a[i] = 0;