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.\" ========================================================================
.\"
.IX Title "pods::SDL::Cookbook::OpenGL 3pm"
.TH pods::SDL::Cookbook::OpenGL 3pm "2020-11-09" "perl v5.32.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
SDL::Cookbook::OpenGL \- Using SDL with OpenGL
.SH "CATEGORY"
.IX Header "CATEGORY"
Cookbook
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
As of release 2.5 \s-1SDL\s0 no longer maintains it's own bindings of OpenGL. Support for OpenGL has been moved over to a more mature implementation.
.PP
This implementation is the \s-1POGL\s0 project. OpenGL is faster and more complete; and works with \s-1SDL\s0 seamlessly.
.SS "\s-1EXAMPLE\s0"
.IX Subsection "EXAMPLE"
Expanded from Floyd-ATC's OpenGL example.
.PP
.Vb 9
\&        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);
.Ve
.PP
You can use OpenGL as needed here.
.PP
.Vb 1
\&        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;
.Ve
.PP
SDLx::App can start an OpenGL application with the parameter gl => 1.
.PP
.Vb 5
\&        glEnable(GL_DEPTH_TEST);
\&        glMatrixMode(GL_PROJECTION);
\&        glLoadIdentity;
\&        gluPerspective(60, $WIDTH / $HEIGHT, 1, 1000);
\&        glTranslatef(0, 0, \-20);
.Ve
.PP
Above we enable \s-1GL\s0 and set the correct perspective
.PP
.Vb 7
\&        while (1) {
\&          &handlepolls;
\&          glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
\&          glRotatef(.1, 1, 1, 1);
\&          &drawscene;
\&          $SDLAPP\->sync;
\&        }
.Ve
.PP
For SDLx::App sync handles the \s-1GL\s0 buffer clean.
.PP
.Vb 2
\&        sub drawscene {
\&          my ($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(@$coords);
\&            }
\&          }
\&
\&          glEnd;
\&
\&          return "";
\&        }
.Ve
.PP
Below we can use SDL::Events as normal:
.PP
.Vb 2
\&        sub handlepolls {
\&          my ($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\en", $SDLEVENT\->motion_x, $SDLEVENT\->motion_y, $SDLEVENT\->motion_xrel, $SDLEVENT\->motion_yrel) }
\&            elsif ($type == 2) { print "You are pressing $key\en" }
\&            elsif ($type == 3) { print "You released $key\en" }
\&            elsif ($type == 12) { exit }
\&            else { print "TYPE $type UNKNOWN!\en" }
\&
\&            if ($type == 2) {
\&              if ($key eq "q" or $key eq "escape") { exit }
\&            }
\&          }
\&
\&          return "";
\&        }
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
perl SDLx::App OpenGL
.SH "AUTHORS"
.IX Header "AUTHORS"
See \*(L"\s-1AUTHORS\*(R"\s0 in \s-1SDL\s0.