I decided I wanted to do some graphics earlier this month, so I pulled down the openGL module and started gnawing on the spinning cube demo that came with it.
I quickly found that it is very easy to break things, blind your viewpoint and generally mess things up with transformations being off. And I also found that it took forever to see what was going on when I had to run the script over and over.
So I thought; hey, this is a scripting language. Let me use the power of the eval, and have it do the work for me!
And thus I split it into two scripts. One with the basics to initialize and loop, the other to edit while it is being continuously re-evaled. Now, I can add a minus sign to a formula, and see the results immediately on screen. I can start defining a polygon or triangle strip, and watch as the shape grows when I enter new points.
I would say it has sped up everything by 10x, since I can just try things effortlessly, and actually *see* the differences flip back and forth.
Readmore for Sample code :
Main loop
#!/usr/bin/perl -w
use strict;
use warnings;
use OpenGL qw/ :all /;
use constant R30D => 0.523598776;
eval {glutInit(); 1} or die qq
{
This requires GLUT.
};
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH | GLUT_ALPHA)
+;
glutInitWindowSize(500, 500);
my $Window_ID = glutCreateWindow( "Open Gl Window" );
# Register the callback function to do the drawing.
glutDisplayFunc(\&cbRenderScene);
# If there's nothing to do, draw.
glutIdleFunc(\&cbRenderScene);
# It's a good idea to know when our window's resized.
glutReshapeFunc(\&resizeEvent);
# And let's get some input.
# glutKeyboardFunc(\&cbKeyPressed);
# glutSpecialFunc(\&cbSpecialKeyPressed);
# glutPassiveMotionFunc(\&mouseMove);
# glutMotionFunc(\&mouseMove);
# glutMouseFunc(\&mouseClick);
# Pass off control to OpenGL.
# Above functions are called as appropriate.
glutMainLoop();
exit 0;
sub resizeEvent
{
my ($Width, $Height) = @_;
print "Resize: $Width, $Height\n";
# Let's not core dump, no matter what.
$Height = 1 if ($Height <1);
glViewport(0, 0, $Width, $Height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0,$Width/$Height,0.1,100.0);
glMatrixMode(GL_MODELVIEW);
$main::window_Width = $Width;
$main::window_Height = $Height;
}
sub cbRenderScene
{
eval {do 'drawframe.pl';};
print $@ . "\r";
# Take a quick nap to avoid wasting CPU
select (undef,undef,undef,0.1);
}
And a demo drawframe.pl which renders some colored hexagons.
no warnings;
# Draw a grid of hexagons
glMatrixMode(GL_MODELVIEW);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1,1,0);
glPointSize(10);
glLineWidth(1);
glDisable(GL_DEPTH_TEST);
glLoadIdentity();
glTranslatef(-5,-8,-30);
glPushMatrix();
glTranslatef(0,0,0);
for my $x (0..10)
{
glTranslatef(cos(R30D),sin(R30D),0);
glPushMatrix();
for my $y(0..10)
{
glTranslatef(0,1,0);
drawHex([$x%2,$y%2,0], [0,.5-$y/20,$y/10]);
}
glPopMatrix();
}
glPopMatrix();
glutSwapBuffers();
sub drawHex
{
my $border=shift;
my $fill = shift;
my $r = shift || 0.5;
my $bwidth = shift || 0.05;
$r = $r-2*$bwidth;
my $s = $r / cos(R30D);
my $h = $s * sin(R30D);
#print "$h, $r, $s";
if (defined $fill)
{
glColor3f(@$fill);
glBegin(GL_POLYGON);
glVertex2f($bwidth+$h,-$r);
glVertex2f($bwidth+$h+$s,-$r);
glVertex2f($bwidth+2*$h+$s,0);
glVertex2f($bwidth+$h+$s, $r);
glVertex2f($bwidth+$h, $r);
glVertex2f($bwidth,0);
glEnd();
}
if (defined $border)
{
glColor3f(@$border);
glBegin(GL_LINE_LOOP);
glVertex2f($bwidth+$h,-$r);
glVertex2f($bwidth+$h+$s,-$r);
glVertex2f($bwidth+2*$h+$s,0);
glVertex2f($bwidth+$h+$s, $r);
glVertex2f($bwidth+$h, $r);
glVertex2f($bwidth,0);
glEnd();
}
}
