perl opengl test

#!/usr/bin/env perl

use 5.016;
use warnings;
use strict;

use SDL;
use SDL::Video;
use SDL::Event;
use SDL::Events;
use OpenGL;
use Math::Trig;

my $WIDTH = 1440;
my $HEIGHT = 900;
my $FOV = 80;

SDL::init(SDL_INIT_VIDEO);

SDL::Video::set_video_mode($WIDTH, $HEIGHT, 32, SDL_OPENGL);

glShadeModel(GL_SMOOTH);
glCullFace(GL_BACK);
glFrontFace(GL_CCW);
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);

{
    my $fov = tan(deg2rad($FOV/2));
    my $near = 1;
    my $far = 100;
    my $left = $fov * $near;
    my $top = $left * $HEIGHT/$WIDTH;

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glFrustum(-$left, $left, -$top, $top, $near, $far);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

my $o = 0.01;

my $left = -20;
my $right = 20;
my $front = -30;
my $back = -100;
my $depth = 10;
my $centre = 10;

my $c = 0;

my $e = SDL::Event->new;
while (!SDL::Events::poll_event($e) || $e->type != SDL_KEYDOWN || $e->key_sym != SDLK_ESCAPE) {

    glClearColor(0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glBegin(GL_QUADS);

        for (my $n = 0; $n < 1; $n += $o) {
            my $k = $c+$n;

            my $ky1 = cos(2*pi*$k);
            my $ky2 = cos(2*pi*($k+$o));

            my $x1 = $left + $n*($right-$left);
            my $x2 = $x1 + $o*($right-$left);

            for (my $m = 0; $m < 1; $m += $o) {
                my $j = $c+$m;

                my $jy1 = sin(2*pi*$j);
                my $jy2 = sin(2*pi*($j+$o));

                my $z1 = $front + $m*($back-$front);
                my $z2 = $z1 + $o*($back-$front);

                my $front_y1 = $ky1 * $jy1 * $depth - $centre;
                my $front_y2 = $ky2 * $jy1 * $depth - $centre;
                my $back_y1 = $ky1 * $jy2 * $depth - $centre;
                my $back_y2 = $ky2 * $jy2 * $depth - $centre;

                glColor3f($n, $m, 1);

                glVertex3f($x2, $front_y2, $z1);
                glVertex3f($x2, $back_y2, $z2);
                glVertex3f($x1, $back_y1, $z2);
                glVertex3f($x1, $front_y1, $z1);
            }
        }

    glEnd();

    $c += $o;
    $c -= 1 if $c > 1;

    SDL::Video::GL_swap_buffers
}