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ztk-roller-coaster-simulation

by zentara (Archbishop)
on Aug 09, 2005 at 18:03 UTC ( #482340=sourcecode: print w/ replies, xml ) Need Help??

Category: GUI Programming
Author/Contact Info zentara@zentara.net
Description: There was an "advanced perl programming" weekly contest awhile back( now defunct I think". One I entered was a roller coaster simulation. The original contest had various *.rc files to make any kind of coaster track design. I just included a nice one in DATA, to make the script self-contained.
#!/usr/bin/perl
use warnings;
use strict;
use Tk;

# by zentara@zentara.net 
# There was an advanced perl programming contest awhile 
# back to simulate a roller coaster. This was my entry. 

# This approach is a very simple method to simulate 
# the roller-coaster motion. I didn't waste any time 
# on actually computing the velocities or positions, 
# rather I relied on the Law of Conservation of Energy, 
# which says that the sum of the Kinetic and Potential 
# Energies will remain constant. The initial total energy  
# is the potential energy at the highest point, and that 
# is released into kinetic energy( i.e. velocity) as the 
# coaster drops.  So as the coaster drops,  
# it's KE increases, and as the coaster climbs it's KE 
# decreases, and stalls if it climbs past it's start height. 
#  
# I figured this was the best approach, since we don't have  
# an actual equation to differentiate to get the instantaneous 
# values. So this is not mathematically exact, it ignores the 
# constants in favor of better animation. 
# After all, it's just a visual simulation,   


$|++;

my %segs =();
my $count = 0;       # holds how many segments there are 
my $action = 0;      # action flag 
my $cur_loc = 1;     # holds current segment in case of stop run 
my $cur_ke  = 0;     # initial kinetic energy 
my $g  = 10;         # gravitational acceleration 
my $m = 1;           # mass of coaster  
                     # (left in for possible future Lorentz transforms
+ :-)) 

my $velocity = 0;    # speedometer  :-) 

while(<DATA>){
    $count++;
    chomp;
    next if /^\s*#/ || /^\s*$/; #skip comments and blank lines  
    my ($x, $y) = split(/\s+/, $_);
    $segs{$count} = [$x, (400 - $y) ]; #inverse coords   
}


my $mw = tkinit;
$mw->geometry("650x450+100+100");

my $canvas = $mw->Canvas(-width => 620, -height => 420,
                         -bg => 'black')->pack();

my @s;
 foreach (1..$count){
   my @str = ( ${$segs{$_}}[0], ${$segs{$_}}[1] );
   push @s, @str;
}

my $curve = $canvas->createLine( @s,
                          -width => 5,
                          -smooth => 1,
                          -fill => 'lightgreen');

my $coaster = $canvas->createOval(${$segs{1}}[0] - 5,${$segs{1}}[1] - 
+5,
                                  ${$segs{1}}[0] + 5 ,${$segs{1}}[1] +
+ 5,
                                  -fill => 'yellow');

my $group = $canvas->createGroup([${$segs{1}}[0],${$segs{1}}[1]],
                                          -members => [$coaster]);

my $subframe = $mw->Frame(-background =>'gray50')->pack(-fill => 'x');

$subframe->Button(-text =>'Exit',
            -background => 'hotpink',
            -activebackground => 'red',
            -command => sub{ exit }
            )->pack(-side=>'left',-padx=>40);

$subframe->Button(-text =>'Slower',
            -background => 'lightyellow',
            -activebackground => 'yellow',
            -command => sub{ if($g < 3)
                         { print chr(07);return}
                         else{$g *= .8; print "$g\n"; } } #not too slo
+w :-) 
            )->pack(-side=>'left',-padx=>40);

$subframe->Label(-text =>'Velocity ',
            -background => 'black',
            -foreground => 'green',
            )->pack(-side=>'left');
       
            
$subframe->Label(-textvariable => \$velocity,
            -width => 5,
            -background => 'black',
            -foreground => 'green',
            )->pack(-side=>'left');

$subframe->Button(-text =>'Faster',
            -background => 'lightgreen',
            -activebackground => 'green',
            -command => sub{ $g *= 1.25; print "$g\n"; }
            )->pack(-side=>'left',-padx=>40);

my $actbut;
$actbut = $subframe->Button(-text =>'Start',
              -background =>'lightsteelblue',
              -activebackground =>'lightskyblue',
              -command => sub { &action($cur_loc,$cur_ke) },
             )->pack(-side=>'right',-padx=>40);

MainLoop;

######################################################################
+# 
sub action {

  if( $actbut->cget(-text) eq 'Start'){
            $actbut->configure(-text=>'Stop');
            $action = 1;
    }else{
            $actbut->configure(-text=>'Start');
            $action = 0;
    }

my ($cur_seg,$cur_ke,) = @_;
my $dt;

#   potential energy at start 
  my $pe_max = $m*$g*(${$segs{1}}[1]);

#Energy is conserved so at any point 
# pe_max = pe_current + ke_current  
# so  
# ke_current = pe_max - pe_current (both directly proportion to y) 

while( $action ){

    my $cur = $cur_seg;
    my $cur_next = $cur_seg + 1;
     if($cur_next > $count ){ $action = 0;
                              $actbut->configure(-text=>'Start');
                              $cur_next = 1;
                             }
                             
    my $x1 = ${$segs{$cur}}[0];
    my $y1 = ${$segs{$cur}}[1];

    my $x2 = ${$segs{$cur_next}}[0];
    my $y2 = ${$segs{$cur_next}}[1];

     my $dx = $x2 - $x1;
     my $dy = $y2 - $y1;
     my $distance = sqrt( $dx**2 + $dy**2);

# compute average y of segment 
     my $y_ave = ($y2 + $y1)/2;

    $cur_ke = $m*$g*$y_ave - $pe_max;

#print "dy->$dy\tcur_ke->$cur_ke\n"; 

$canvas->move($group, $dx,$dy);
$canvas->update;

   if($cur_next > $count ){ $cur_seg = 1}
         else {$cur_seg++}

# velocity is proportional to the sqrt of ke 
# and time is inverse to velocity         
# $v = $distance/$seconds  
# $seconds = $distance/$v  

  if($cur_ke >= 0){
     my $v = sqrt(2*$cur_ke/$m);
     $dt =  $distance/$v;  # constant 2 added for visual effect  
         if($cur_loc >= $count){
              $cur_loc = 1;
              $cur_ke = 0;
              $dt = .001;
              $velocity = 0;
             }
       $velocity = sprintf('%.1f',$v);
       $velocity = sprintf('%.1f',$v);

       #select(undef,undef,undef,$dt);    
       $mw->after($dt*1000,$canvas->update);
       #it's not the best to use a blocking select in Tk 
       #but it's all in microseconds....so no problem 
       #select takes seconds , after takes microseconds 
     }else{
         my $message =
        'Uh oh, Out of KE, Get out and push. Hit Start to get moving.'
+ ;
          $mw->messageBox(
             -background => 'lightyellow',
             -icon       => 'error',
             -message    => $message,
             -type       => 'OK'
              );
      &restart;
      }

$cur_loc = $cur_seg;
} #end of while loop 

if($cur_loc >= $count){
      $cur_loc = 1;
      $cur_ke = 0;
      $dt = .001;
      $velocity = 0;
  }
}
###################################################### 
sub restart{
  $actbut->configure(-text=>'Start');

$action = 0;      # action flag 
$cur_loc = 1;     # holds current segment in case of stop run 
$cur_ke  = 0;     # initial kinetic energy 
$g = 10;

}
#################################################### 

__DATA__
0 394
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4.71503160037539 374.563732945664
6.06061 369.017
8.64383766277946 359.356413328257
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12.1212 346.352
14.9606189063128 336.763585101046
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18.1818 325.886
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30.303 291.085
34.1461008917288 281.852959297317
36.3636 276.526
40.6402587824946 267.486631125011
42.4242 263.716
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48.4848 252.548
53.8116714994823 244.084877643092
54.5455 242.919
60.4934607710689 234.880233759723
60.6061 234.728
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103.03 209.73
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133.333 215.432
139.394 217.937
145.455 220.74
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157.576 226.994
163.636 230.329
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175.758 237.145
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187.879 243.822
193.939 246.994
200 250
206.061 252.8
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236.364 262.546
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248.485 263.941
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600 250

Comment on ztk-roller-coaster-simulation
Download Code
Re: ztk-roller-coaster-simulation
by chanio (Priest) on Aug 10, 2005 at 04:40 UTC
    Nice!

    Let me contribute by pollishing up the look of your script (you deserve this):

    (just replace your comments and the

    use Tk;
    before them with this...)

    use Getopt::Long; use Pod::Usage; use Tk; my $VERSION='1.00'; =pod =head1 NAME [ TkRollerCoaster.pl ] =head1 DESCRIPTION There was an "advanced perl programming" weekly contest awhile back( +now defunct I think". One I entered was a roller coaster simulation. The original contest h +ad various *.rc files to make any kind of coaster track design. I just included a nice one +in DATA, to make the script self-contained. This approach is a very simple method to simulate the roller-coaster motion. I didn't waste any time on actually computing the velocities or positions, rather I relied on the Law of Conservation of Energy, which says that the sum of the Kinetic and Potential Energies will remain constant. The initial total energy is the potential energy at the highest point, and that is released into kinetic energy( i.e. velocity) as the coaster drops. So as the coaster drops, it's KE increases, and as the coaster climbs it's KE decreases, and stalls if it climbs past it's start height. I figured this was the best approach, since we don't have an actual equation to differentiate to get the instantaneous values. So this is not mathematically exact, it ignores the constants in favor of better animation. After all, it's just a visual simulation, =head2 OPTIONS AND ARGUMENTS (-)-h(elp) Help: shows these options (-)-m(an) man : shows this pod (-)-v(ersion) print Modules, Perl, OS, Program info =item B<--version o -v> Prints module && script versions =item B<man> Man: shows these options =item B<help> Help: shows this pod =back =head1 SYNOPSIS Roller Coaster =head1 SCRIPT CATEGORIES fun =head1 OSNAMES any =head1 AUTHOR zentara #http://perlmonks.org/index.pl?node_id=131741# << zentara@zen +tara.net >> ~ Aug 09, 2005 at 15:03 ART (#482340)~ =cut my ($opt_help, $opt_man, $opt_versions); GetOptions( ## EXPECTED GETOPT: ! JUST MENTION THE WORD 'help!' => \$opt_help, 'man!' => \$opt_man, 'versions!' => \$opt_versions, ) or pod2usage(-verbose => 1 ) && exit; ## EXIT WITH SOME INFO pod2usage(-verbose => 1) && exit if defined $opt_help; pod2usage(-verbose => 2) && exit if defined $opt_man; if(defined $opt_versions) { print "\nModules, Perl, OS, Program info:\n", " Pod::Usage $Pod::Usage::VERSION\n", " Getopt::Long $Getopt::Long::VERSION\n", " strict $strict::VERSION\n", " Perl $]\n", " OS $^O\n", " TkRolerCoaster.pl $VERSION\n", " $0\n", "\n\n"; exit; }
    Then it looks more professional, don't you think so?

    Thank you!

    { \ ( ' v ' ) / }
    ( \ _ / ) _ _ _ _ ` ( ) ' _ _ _ _
    ( = ( ^ Y ^ ) = ( _ _ ^ ^ ^ ^
    _ _ _ _ \ _ ( m _ _ _ m ) _ _ _ _ _ _ _ _ _ ) c h i a n o , a l b e r t o
    Wherever I lay my KNOPPIX disk, a new FREE LINUX nation could be established
      Thanks. I'll update it later. Maybe this is the "nudge" I need to get over my "pod-o-phobia". :-)

      I'm not really a human, but I play one on earth. flash japh

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