/
acp2
executable file
·133 lines (113 loc) · 2.23 KB
/
acp2
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#!/usr/bin/env perl
# see http://www.gamasutra.com/resource_guide/20030121/jacobson_02.shtml
use strict;
use warnings;
use SDL;
use SDL::Event;
use SDLx::App;
my $app = SDLx::App->new(
width => 400,
height => 400,
title => 'Adv. Character Phys. 02');
my $target = {
x => 200,
y => 200,
};
my @ps;
my $ps = 2;
my $ts = 1; # time step;
# init particles
for (1..$ps) {
my $tx = rand 100;
my $ty = rand 100;
push @ps, {
x => $tx,
y => $ty,
ox => $tx,
oy => $ty,
fx => 0,
fy => 0,
};
};
$app->add_event_handler(\&event);
$app->add_move_handler (\&calc);
$app->add_show_handler (\&render);
$app->run();
sub event {
my $event = shift;
my $controller = shift;
$controller->stop if $event->type == SDL_QUIT;
if ($event->type == SDL_MOUSEMOTION) {
$target->{x} = $event->button_x;
$target->{y} = $event->button_y;
}
}
sub apply_force {
my $p = shift;
$p->{fx} = 2;
$p->{fy} = 1;
}
sub limrng {
my $v = shift;
my $l = shift;
my $h = shift;
return ($v<$l ? $l : ($v>$h ? $h : $v));
}
sub verlet {
my $p = shift;
my $tx = $p->{x};
my $ty = $p->{y};
$p->{x} += $p->{x}-$p->{ox} + $p->{fx}*$ts*$ts;
$p->{y} += $p->{y}-$p->{oy} + $p->{fy}*$ts*$ts;
$p->{ox} = $tx;
$p->{oy} = $ty;
}
sub con_cube {
my $p = shift;
my $xl = shift; # [xy][lh]; l->low, h->high
my $xh = shift;
my $yl = shift;
my $yh = shift;
$p->{x} = limrng $p->{x}, $xl, $xh;
$p->{y} = limrng $p->{y}, $yl, $yh;
}
sub con_stick {
my $p1 = shift;
my $p2 = shift;
my $restlen = shift;
my $dx = $p2->{x} - $p1->{x};
my $dy = $p2->{y} - $p1->{y};
my $dlen = ($dx**2 + $dy**2) ** 0.5;
my $diff = ($dlen-$restlen) / $dlen / 2;
$p1->{x} += $dx*$diff;
$p1->{y} += $dy*$diff;
$p2->{x} -= $dx*$diff;
$p2->{y} -= $dy*$diff;
}
sub calc {
my ($step, $app) = @_;
$ts = $step;
foreach my $i (0..$#ps) {
apply_force $ps[$i];
verlet $ps[$i];
}
# satisfy constraints
foreach (1..10) {
foreach my $i (0..$#ps) {
con_cube $ps[$i], 0, 200, 0, 200;
}
con_stick $ps[0], $ps[1], 30;
}
}
sub drawp {
my $p = shift;
$app->draw_circle_filled([$p->{x}, $p->{y}], 5, [255, 0, 0, 255]);
}
sub render {
my ($delta, $app) = @_;
$app->draw_rect([0, 0, $app->w, $app->h], 0); # clear screen
foreach my $i (0..$#ps) {
drawp $ps[$i];
}
$app->update();
}