/* chain_maker.txt */

/* This script builds an interlocking chain of torii that follows
   selected paths.  Each link is a separate mesh to allow easier tweaks.
   
   Adjust the four parameters below to customize the chain.
   
   The script uses the techniques shown in R. Steven Glanville's 
   demo script "spine.txt".
   It also borrows from Tyson Collins's "torus_plugin.an8"
   
   NickE
*/

object $curObject;
shape $shape, $shapes[0], $childShapes[1];
int $numSplines,$ii,$jj;
point3 $p0, $p1;
quaternion $q0;


shape $link;
int $sides[2],$segments[2],$swap,$segment,$lastsegment,$cursegment,$i;
int $numlinks,$ll,$holdpoint;
int $elongation[2],$halfsegments[2];
float $segradius[2],$innerradius[2],$angle,$linkoffset;
point3 $vertex[100];
point3 $p;
int $vertexindex[80];
int $mod;

$sides[0] = 12;				               /* more makes smoother walled links */
$segments[0] = 12;			             /* more makes more circular links */
$halfsegments[0] = $segments[0] / 2;
$segradius[0] = 2;		              /* the thickness of the link */
$innerradius[0] = 5;		            /* from the center of walls across the "hole" of the link */
$elongation[0]=5;				            /* the elongation factor */

$sides[1] = 12;				
$segments[1] = 12;			  
$halfsegments[1] = $segments[1] / 2;
$segradius[1] = 2;		
$innerradius[1] = 6;		
$elongation[1]=0;				


/* actual hole radius is $innerradius[] - $segradius[] 
   Make sure to set ($innerradius[] - $segradius[] + $elongation[]) >= (2 * $segradius[])
   or you will have overlap
   
   If the difference between the $innerradius[] and the $segradius[] is large
   and the path length is low, you will get links spacing overlap
*/
$curObject = project.curObject;
$curObject.GetShapes($childShapes);
$shapes.size = 0;
while ($childShapes.size > 0)
    $shapes.push($childShapes.pop());

while ($shapes.size > 0) {
    $shape = $shapes.pop();

    if ($shape.GetKind() == SHAPE_KIND_PATH && $shape.Selected) {
        $numSplines = $shape.GetNumSplines();
        for $ii = 0 to $numSplines - 1 do {
            spline $spline;
            float $length, $t;
            int $num, $prev;
            float4x4 $xformMat;

            $spline = $shape.GetSpline($ii);
            $length = $spline.GetLength();
    
            $num = 2*($length / (((2*$innerradius[0]) - (2*$segradius[0]) + ($elongation[0])) + ((2*$innerradius[1]) - (2*$segradius[1]) + ($elongation[1]))));
			/*  the denominator above sets the relationship of the links */
			
            for $jj = 0 to $num do {

                $link=mesh();
                $link.Open();

                $mod = ($jj % 2);
                $t = $jj/($num*1.0);
                $p0 = $spline.Eval($t);
                $q0 = $spline.Orientation($t);
                $xformMat = toFloat4x4($q0);

                for $i = 0 to $sides[$mod]-1 do
                {
                
                  if (($mod) == 0) {
                     $vertex[$i].x = cos((2*3.14159*$i)/$sides[$mod])*$segradius[$mod] + $innerradius[$mod];
                     $vertex[$i].y = sin((2*3.14159*$i)/$sides[$mod])*$segradius[$mod];
                     $vertex[$i].z = 0.0;
                  } else {
                     $vertex[$i].z = cos((2*3.14159*(($sides[$mod]-1)-$i))/$sides[$mod])*$segradius[$mod] + $innerradius[$mod];
                     $vertex[$i].x = sin((2*3.14159*(($sides[$mod]-1)-$i))/$sides[$mod])*$segradius[$mod];
                     $vertex[$i].y = 0.0;
                  }
                } 
                $vertexindex[$sides[$mod]+1] = $vertexindex[0];
                $lastsegment = 0;
                $cursegment = $segments[$mod]+1;
                for $segment = 0 to $halfsegments[$mod] do
                {
                   $angle = (2*3.14159)*($segment * (1.0/$segments[$mod]));
                   for $i = 0 to $sides[$mod]-1 do 
                   {
                      if (($jj % 2) == 0) {
     	                   $p.y = $vertex[$i].y;
                         $p.z = cos($angle)*$vertex[$i].z + sin($angle)*$vertex[$i].x + ($elongation[$mod]/2.0);
	                       $p.x = -sin($angle)*$vertex[$i].z + cos($angle)*$vertex[$i].x;
	                       $p1 = $xformMat.Project($p) + $p0;
                      } else {
    	                   $p.x = $vertex[$i].x;
                         $p.z = cos($angle)*$vertex[$i].y + sin($angle)*$vertex[$i].z + ($elongation[$mod]/2.0);
	                       $p.y = -sin($angle)*$vertex[$i].y+ cos($angle)*$vertex[$i].z;
	                       $p1 = $xformMat.Project($p) + $p0;
                      }

                      $vertexindex[$cursegment + $i] = $link.AddPoint($p1);
                   }
                   $vertexindex[$cursegment + $sides[$mod]] = $vertexindex[$cursegment];
                   if ($segment != 0) {
                      for $i = 0 to $sides[$mod] - 1 do
                      {

                        $link.OpenFace(0, 0);
                        $link.VertexN($vertexindex[$lastsegment + $i]);
                        $link.VertexN($vertexindex[$cursegment + $i]);
                        $link.VertexN($vertexindex[$cursegment + $i + 1]);
                        $link.VertexN($vertexindex[$lastsegment + $i + 1]);
                        $link.CloseFace();

                      }
                   }
                   $swap = $lastsegment;
                   $lastsegment = $cursegment;
                   $cursegment = $swap;
                }

                for $segment = $halfsegments[$mod] to $segments[$mod] do
                {
                   $angle = (2*3.14159)*($segment * (1.0/$segments[$mod]));
                   for $i = 0 to $sides[$mod]-1 do 
                   {
                      if (($jj % 2) == 0) {
     	                   $p.y = $vertex[$i].y;
                         $p.z = cos($angle)*$vertex[$i].z + sin($angle)*$vertex[$i].x - ($elongation[$mod]/2.0);
	                       $p.x = -sin($angle)*$vertex[$i].z + cos($angle)*$vertex[$i].x;
	                       $p1 = $xformMat.Project($p) + $p0;
                      } else {
     	                   $p.x = $vertex[$i].x;
                         $p.z = cos($angle)*$vertex[$i].y + sin($angle)*$vertex[$i].z - ($elongation[$mod]/2.0);
	                       $p.y = -sin($angle)*$vertex[$i].y + cos($angle)*$vertex[$i].z;
	                       $p1 = $xformMat.Project($p) + $p0;
                      }
                      $vertexindex[$cursegment + $i] = $link.AddPoint($p1);
                   }
                   $vertexindex[$cursegment + $sides[$mod]] = $vertexindex[$cursegment];
                   if ($segment != 0) {
                      for $i = 0 to $sides[$mod] - 1 do
                      {

                        $link.OpenFace(0, 0);
                        $link.VertexN($vertexindex[$lastsegment + $i]);
                        $link.VertexN($vertexindex[$cursegment + $i]);
                        $link.VertexN($vertexindex[$cursegment + $i + 1]);
                        $link.VertexN($vertexindex[$lastsegment + $i + 1]);
                        $link.CloseFace();
                                                
                      }
                   }
                   $swap = $lastsegment;
                   $lastsegment = $cursegment;
                   $cursegment = $swap;
                }

                for $i = 0 to $sides[$mod]-2 do {
                  $link.OpenFace(0, 0);
                  $link.VertexN($vertexindex[$lastsegment + $i]); 
                  $link.VertexN($i);
                  $link.VertexN($i+1);
                  $link.VertexN($vertexindex[$lastsegment + $i+1]);
                  $link.CloseFace();
                }
                $link.OpenFace(0, 0);
                $link.VertexN(0);
                $link.VertexN($vertexindex[$lastsegment]); 
                $link.VertexN($vertexindex[$lastsegment + $sides[$mod]-1]);
                $link.VertexN($sides[$mod]-1);
                $link.CloseFace();

                $link.Close();                
            }
        }
    }
}