good chemistry is complicated,and a little bit messy -LW PerlMonks

### Re: Rotation around an axis clockwise and anti-clockwise algorithm question?

by zentara (Archbishop)
 on Jun 13, 2012 at 13:25 UTC ( #975974=note: print w/replies, xml ) Need Help??

Amplifying on what others said about using matrix operations, I was wondering if you want to give your program a visualization GUI? If so, I would like to mention Tk::Zinc and Gtk2's Goo::Canvas. The Zinc canvas does matrix rotations, and is very good at maintaining accuracy of its matrix with tset and tget. I'm disappointed that its parent website has seem to have disappeared, as Zinc was great.

The Goo canvas is still alive and well and being developed. In both their rotation algorithms, you can specify negative angles. As a matter of fact, a good vector equation should accept negative angles and deal with them properly within its coordinate system.

Here is a simple Goo canvas positive and negative angle rotation example.

```#!/usr/bin/perl -w
use strict;
use warnings;
use Goo::Canvas;
use Gtk2 '-init';
use Glib qw(TRUE FALSE);

my \$window = Gtk2::Window->new('toplevel');
\$window->signal_connect('delete_event' => sub { Gtk2->main_quit; });
\$window->set_size_request(640, 600);

my \$swin = Gtk2::ScrolledWindow->new;

my \$canvas = Goo::Canvas->new();
\$canvas->set_size_request(800, 650);
\$canvas->set_bounds(0, 0, 1000, 1000);
my \$root = \$canvas->get_root_item();

# first offset set
my \$pts_ref = [50,50,180,120,90,100,50,50];
my \$line = Goo::Canvas::Polyline->new(
\$root, TRUE,
\$pts_ref,
'stroke-color' => 'black',
'line-width' => 3,
'fill-color-rgba' => 0x3cb37180,
);

my (\$midx, \$midy) = _get_CM( @\$pts_ref );

my \$ellipse = Goo::Canvas::Ellipse->new(
\$root, \$midx-2, \$midy-2,\$midx+2, \$midy+2,
'stroke-color' => 'goldenrod',
'line-width' => 8
);

my \$ellipse1 = Goo::Canvas::Ellipse->new(
\$root, -2, -2, +2, +2,
'stroke-color' => 'black',
'line-width' => 4
);

\$ellipse1->translate(\$midx,\$midy);
# end first set

#if you have equilateral shapes it's
#possible to make at origin and translate
my \$group = Goo::Canvas::Group->new(\$root);
my \$pts_ref1 = [-60,0, 60,0, 0, 40, -60, 0];
my \$line1 = Goo::Canvas::Polyline->new(
\$group, TRUE,
\$pts_ref1,
'stroke-color' => 'black',
'line-width' => 3,
'fill-color-rgba' => 0xffb37180,
);

my (\$midx1, \$midy1) = _get_CM( @\$pts_ref1 );
print "\$midx1, \$midy1\n";

my \$ellipse2 = Goo::Canvas::Ellipse->new(
\$group, -2, -2, +2, +2,
'stroke-color' => 'black',
'line-width' => 4
);

\$ellipse2->translate(0,\$midy1 + 4);

my \$ellipse3 = Goo::Canvas::Ellipse->new(
\$group,
,-60,-60,60,60,
'stroke-color' => 'green',
'line-width' => 4
);

\$ellipse3->translate(60,60);

#move whole group
\$group->translate(400,400);

my \$id = Glib::Timeout->add (10, sub {
\$line->rotate (10, \$midx, \$midy);
\$group->rotate (-1, 0, 0 );
return 1;
});

\$window->show_all();
Gtk2->main;

#################################################################
# This sub finds the center of mass of a polygon.
# I grabbed the algorithm somewhere from the web.
# I grabbed it from Ala Qumsieh's RotCanvas :-)
sub _get_CM {
my (\$x, \$y, \$area);

my \$i = 0;

while (\$i < \$#_) {
my \$x0 = \$_[\$i];
my \$y0 = \$_[\$i+1];

my (\$x1, \$y1);
if (\$i+2 > \$#_) {
\$x1 = \$_[0];
\$y1 = \$_[1];
} else {
\$x1 = \$_[\$i+2];
\$y1 = \$_[\$i+3];
}

\$i += 2;

my \$a1 = 0.5*(\$x0 + \$x1);
my \$a2 = (\$x0**2 + \$x0*\$x1 + \$x1**2)/6;
my \$a3 = (\$x0*\$y1 + \$y0*\$x1 + 2*(\$x1*\$y1 + \$x0*\$y0))/6;
my \$b0 = \$y1 - \$y0;

\$area += \$a1 * \$b0;
\$x    += \$a2 * \$b0;
\$y    += \$a3 * \$b0;
}

return split ' ', sprintf "%.0f %0.f" => \$x/\$area, \$y/\$area;
}
####################################################################
__END__

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh
• Comment on Re: Rotation around an axis clockwise and anti-clockwise algorithm question?

Create A New User
Node Status?
node history
Node Type: note [id://975974]
help
Chatterbox?
 [Discipulus]: problematic? i came back after just a week of course, I forgo teverything..

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (5)
As of 2017-12-18 11:22 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?
What programming language do you hate the most?

Results (483 votes). Check out past polls.

Notices?