// Spiral Maker

// Created by Brian Baker, comharsa@clara.net

// March 2000

//

// Creates a pseudo-spiral based on semicircles.

// Once drawn change the stroke to whatever you want.

// get details of spiral required

var userInfo = prompt ("Please enter two numbers, separated by a comma (eg 5, 20).\nThe first is the number of turns needed, and the second is the distance in pixels between each turn. Neither can be zero.\nNote: large numbers of turns can take a long time to process.");

var spirInfo = userInfo.split(",",2);

// check info useable

if (isNaN(spirInfo[0]) == true || isNaN(spirInfo[1]) == true || spirInfo[0] == 0 || spirInfo[1] == 0)

         {

         // inform user of error

         alert ("The entry did not consist of two useable numbers. Please try again.");

         }

else

         {

         // get centre of document

         var docWidth = fw.getDocumentDOM().width;

         var docHeight = fw.getDocumentDOM().height;

         // draw centre point

         fw.getDocumentDOM().addNewSinglePointPath({x:docWidth/2, y:(docHeight/2)+(spirInfo[1]/2)}, {x:docWidth/2, y:docHeight/2}, 

{x:docWidth/2, y:(docHeight)/2-(spirInfo[1]/2)}, true);

         // draw spiral

         var i = 1;

         for (var j = 1; j <= spirInfo[0] ; j++)

                  {

                  fw.getDocumentDOM().appendPointToPath(0, i, {x:(docWidth/2)-(spirInfo[1]/2), y:(docHeight/2)-(((2*j)-1)*(spirInfo[1]/2))}, 

{x:(docWidth/2)-(spirInfo[1]/2), y:(docHeight/2)-(((2*j)-1)*(spirInfo[1]/2))}, {x:(docWidth/2)-(spirInfo[1]/2), y:(docHeight/2)-(((2*j)-1)*(spirInfo[1]/2))});

                  i++;

                  fw.getDocumentDOM().appendPointToPath(0, i, {x:(docWidth/2)-j*spirInfo[1], y:(docHeight/2)-(((2*j)-1)*(spirInfo[1]/2))}, 

{x:(docWidth/2)-j*spirInfo[1], y:(docHeight/2)}, {x:(docWidth/2)-j*spirInfo[1], y:(docHeight/2)+j*spirInfo[1]});

                  i++;

                  fw.getDocumentDOM().appendPointToPath(0, i, {x:docWidth/2, y:(docHeight/2)+(j*spirInfo[1])}, {x:docWidth/2, y:(docHeight/2)+(j*spirInfo[1])}, {x:docWidth/2, y:(docHeight/2)+(j*spirInfo[1])});

                  i++;

                  fw.getDocumentDOM().appendPointToPath(0, i, {x:(docWidth/2)+(j*spirInfo[1]), y:(docHeight/2)+(j*spirInfo[1])}, 

{x:(docWidth/2)+(j*spirInfo[1]), y:(docHeight/2)}, {x:(docWidth/2)+(j*spirInfo[1]), y:(docHeight/2)-((2*j+1)*(spirInfo[1]/2))});

                  i++;

                  }

}