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#!/usr/bin/perl
# Purpose: Simple demo of per-pixel lighting with GLSL and OpenGL::Shader
# Copyright (c) 2007, Geoff Broadwell; this script is released
# as open source and may be distributed and modified under the terms
# of either the Artistic License or the GNU General Public License,
# in the same manner as Perl itself. These licenses should have been
# distributed to you as part of your Perl distribution, and can be
# read using `perldoc perlartistic` and `perldoc perlgpl` respectively.
use strict;
use warnings;
use OpenGL ':all';
use OpenGL::Shader;
use Time::HiRes 'time';
our $VERSION = '0.1.0';
my $width = 1000;
my $height = 1000;
my ($frames, $start);
my ($window, $teapot);
my ($shader, $shader_enabled);
go();
sub go {
# Simple usage
print "Press 'Q' or 'Esc' to exit, or any other key to toggle shader.\n";
# GLUT setup
glutInit;
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowSize($width, $height);
$window = glutCreateWindow('Shader Test');
glutIdleFunc (\&cb_draw);
glutDisplayFunc (\&cb_draw);
glutKeyboardFunc(\&cb_keyboard);
# Shader program
$shader = new OpenGL::Shader('GLSL');
die "This program requires support for GLSL shaders.\n" unless $shader;
my $fragment = fragment_shader();
my $vertex = vertex_shader();
my $info = $shader->Load($fragment, $vertex);
print $info if $info;
toggle_shader();
# Display list for teapot
$teapot = glGenLists(1);
glNewList($teapot, GL_COMPILE);
glutSolidTeapot(1);
glEndList;
# Unchanging GL config
glViewport(0, 0, $width, $height);
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
glLoadIdentity;
gluPerspective(90, $width/$height, 1, 10);
glMatrixMode(GL_MODELVIEW);
glShadeModel(GL_SMOOTH);
glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, GL_TRUE);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glLightfv_p(GL_LIGHT0, GL_POSITION, 4, 4, 4, 1);
glMaterialfv_p(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, 1, .7, .7, 1);
glMaterialfv_p(GL_FRONT_AND_BACK, GL_SPECULAR, 1, 1, 1, 1);
glMaterialf (GL_FRONT_AND_BACK, GL_SHININESS, 50 );
# Actually start the test
$start = time;
glutMainLoop;
}
sub cb_draw {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity;
glTranslatef(0, 0, -3);
my $slow_time = time / 5;
my $frac_time = $slow_time - int $slow_time;
my $angle = $frac_time * 360;
glRotatef($angle, 0, 1, 0);
glRotatef(30, 1, 0, 0);
glCallList($teapot);
glutSwapBuffers;
$frames++;
}
sub cb_keyboard {
my $key = shift;
my $chr = lc chr $key;
if ($key == 27 or $chr eq 'q') {
my $time = time - $start;
my $fps = $frames / $time;
printf "%.3f FPS\n", $fps;
glutDestroyWindow($window);
exit(0);
}
else {
toggle_shader();
}
}
sub toggle_shader {
$shader_enabled = !$shader_enabled;
$shader_enabled ? $shader->Enable : $shader->Disable;
}
sub vertex_shader {
return <<'VERTEX';
varying vec3 Normal;
varying vec3 Position;
void main(void) {
gl_Position = ftransform();
Position = vec3(gl_ModelViewMatrix * gl_Vertex);
Normal = gl_NormalMatrix * gl_Normal;
}
VERTEX
}
sub fragment_shader {
return <<'FRAGMENT';
varying vec3 Position;
varying vec3 Normal;
void main(void) {
vec3 normal = normalize(Normal);
vec3 reflected = normalize(reflect(Position, normal));
vec3 light_dir = normalize(vec3(gl_LightSource[0].position) - Position);
float diffuse = max (dot(light_dir, normal ), 0.0);
float spec = clamp(dot(light_dir, reflected), 0.0, 1.0);
spec = pow (spec, gl_FrontMaterial.shininess);
gl_FragColor = gl_FrontLightModelProduct.sceneColor
+ gl_FrontLightProduct[0].ambient
+ diffuse * gl_FrontLightProduct[0].diffuse
+ spec * gl_FrontLightProduct[0].specular;
}
FRAGMENT
}
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