draw an archimedian spiral approximation (w/ cubic bezier curves) in iDraw/Graphic

spiral.idplugin.js

// spiral.idplugin

function drawSegment (doc, radius, iterations) {
    var path = [doc addPath]
    var spread = radius / 4
    var c = 0.552284749

    [path addMoveTo:CGPointMake(radius, 0)]

    while (--iterations) {
        var oldRadius

        [path addCurveTo:CGPointMake(0, radius) controlPoint1:CGPointMake(radius, radius * c) controlPoint2:CGPointMake(radius * c, radius)]
        oldRadius = radius
        radius += spread
        [path addCurveTo:CGPointMake(-radius, 0) controlPoint1:CGPointMake(-radius * c, oldRadius) controlPoint2:CGPointMake(-radius, oldRadius * c)]
        oldRadius = radius
        radius += spread
        [path addCurveTo:CGPointMake(0, -radius) controlPoint1:CGPointMake(-oldRadius, -radius * c) controlPoint2:CGPointMake(-oldRadius * c, -radius)]
        oldRadius = radius
        radius += spread
        [path addCurveTo:CGPointMake(radius, 0) controlPoint1:CGPointMake(radius * c, -oldRadius) controlPoint2:CGPointMake(radius, -oldRadius * c)]
    }

    return path;
}

function init() {
    var doc = [app activeDocument]

    var path = drawSegment(doc, 16, 12)

    [[doc activeLayer] addPathShape:path]
}

init()