#!/usr/bin/perl
# This program takes in a filename, and outputs pov code to
# produce a spider web.  You currently have to hand edit
# The following variables to move things around.
# CENT= Center of the web
$CENT="<0,0,0>";

# Number of loops around the web
$NUM_RINGS=8;

# Radius of the web strings
$STRING_RAD=0.05;

# The webs made of blobs this is the STRENGTH
$STRING_TEN=1;

# The webs THRESHOLD
$THRESHOLD=0.65;

# The points are the anchor points for the web
# Example:

#       X           X
#
#             0        X
#
#           X     X
# 
# 0 = center
# X = anchor points
# 
@points= ("<0,1,0>", "<.5,.5,0>", "<1,0,0>",
          "<.5,-.5,0>", "<0,-1,0>", "<-.5,-.5,0>",
          "<-1,0,0>", "<-.5,.5,0>");

($outfile) = @ARGV;

open (OUTFILE, ">$outfile") || die "Could not open $outfile.\n";

print OUTFILE "#declare CENT = $CENT\n";
print OUTFILE "#declare NUM_RINGS = $NUM_RINGS\n";
print OUTFILE "#declare STRING_RAD = $STRING_RAD\n";
print OUTFILE "#declare STRING_TEN = $STRING_TEN\n";

$i=0;
foreach (@points) {
   print OUTFILE "#declare P$i = $_\n";
   print OUTFILE "#declare D$i = (P$i - CENT ) / NUM_RINGS\n";
   $i++;
}
print OUTFILE "// #declare web =\nunion {\n";
print OUTFILE "   blob {\n";
print OUTFILE "      threshold .65\n";
$i2=0;
while ($i2 < $i) {
   print OUTFILE "      cylinder { CENT P$i2 STRING_RAD STRING_TEN }\n";
   $i2++;
}
print OUTFILE "   }\n";
print OUTFILE "   #declare Z = 1\n";
print OUTFILE "   #while ( Z < NUM_RINGS )\n";
$i2=0;
while ($i2 < $i) {
   print OUTFILE "      #declare V$i2=<CENT.x+D$i2.x*Z, CENT.y+D$i2.y*Z, CENT.z+D$i2.z*Z>\n";
   $i2++;
}  
# need to take care of last one also.
print OUTFILE "      blob {\n";
print OUTFILE "         threshold $THRESHOLD\n";
$i2=0;
$i--;
while ($i2 < $i) {
   print OUTFILE "         cylinder { V$i2 V";
   print OUTFILE $i2+1;
   print OUTFILE " STRING_RAD, STRING_TEN }\n";
   $i2++;
} 
print OUTFILE "         cylinder { V$i2 V0 STRING_RAD, STRING_TEN }\n";

print OUTFILE "      }\n";
print OUTFILE "      #declare Z=Z+1\n";
print OUTFILE "   #end // while\n";
print OUTFILE "   pigment { White }\n";
print OUTFILE "   finish { Shiny }\n";
print OUTFILE "}";