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SDL::Cookbook::OpenGL - Using SDL with OpenGL

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Cookbook

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As of release 2.5 SDL no longer maintains it's own bindings of openGL. Support for openGL has been moved over to a more mature implementation.

This implementation is the POGL project. OpenGL is faster and more complete; and works with SDL seemlessly.

EXAMPLE

Expanded from Floyd-ATC's OpenGL example.



	use strict;
	use warnings;
	use SDL;
	use SDLx::App;
	use SDL::Mouse;
	use SDL::Video;
	use SDL::Events;
	use SDL::Event;
	use OpenGL qw(:all);

You can use OpenGL as needed here.

	my ($SDLAPP, $WIDTH, $HEIGHT, $SDLEVENT);

	$| = 1;
	$WIDTH = 1024;
	$HEIGHT = 768;
	$SDLAPP = SDLx::App->new(title => "Opengl App", width => $WIDTH, height => $HEIGHT, gl => 1);
	$SDLEVENT = SDL::Event->new;

SDLx::App can start an OpenGL application with the parameter gl => 1.

	glEnable(GL_DEPTH_TEST);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity;
	gluPerspective(60, $WIDTH / $HEIGHT, 1, 1000);
	glTranslatef(0, 0, -20);

Above we enable GL and set the correct prespective

	while (1) {
	  &handlepolls;
	  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	  glRotatef(.1, 1, 1, 1);
	  &drawscene;
	  $SDLAPP->sync;
	}

For SDLx::App sync handles the GL buffer clean.

	sub drawscene {
	  my ($color, $x, $y, $z);

	  for (-2 .. 2) {
	    glPushMatrix;
	    glTranslatef($_ * 3, 0, 0);
	    glColor3d(1, 0, 0);
	    &draw_cube;
	    glPopMatrix;
	  }

	  return "";
	}




	sub draw_cube {
	  my (@indices, @vertices, $face, $vertex, $index, $coords);

	  @indices = qw(4 5 6 7   1 2 6 5   0 1 5 4
			0 3 2 1   0 4 7 3   2 3 7 6);
	  @vertices = ([-1, -1, -1], [ 1, -1, -1],
		       [ 1,  1, -1], [-1,  1, -1],
		       [-1, -1,  1], [ 1, -1,  1],
		       [ 1,  1,  1], [-1,  1,  1]);

	  glBegin(GL_QUADS);

	  foreach my $face (0..5) {
	    foreach my $vertex (0..3) {
	      $index  = $indices[4 * $face + $vertex];
	      $coords = $vertices[$index];

	      glVertex3d(@$coords);
	    }
	  }

	  glEnd;

	  return "";
	}

Below we can use SDL::Events as normal:

	sub handlepolls {
	  my ($type, $key);

	  SDL::Events::pump_events();

	  while (SDL::Events::poll_event($SDLEVENT)) {
	    $type = $SDLEVENT->type();
	    $key = ($type == 2 or $type == 3) ? $SDLEVENT->key_sym : "";

	    if ($type == 4) { printf("You moved the mouse! x=%s y=%s xrel=%s yrel=%s\n", $SDLEVENT->motion_x, $SDLEVENT->motion_y, $SDLEVENT->motion_xrel, $SDLEVENT->motion_yrel) }
	    elsif ($type == 2) { print "You are pressing $key\n" }
	    elsif ($type == 3) { print "You released $key\n" }
	    elsif ($type == 12) { exit }
	    else { print "TYPE $type UNKNOWN!\n" }

	    if ($type == 2) {
	      if ($key eq "q" or $key eq "escape") { exit }
	    }
	  }

	  return "";
	}

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