Draw Static Enemies
Gtk Invaders
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Now that we have our enemies positioned, we can start moving them. Each frame we move all of the enemies in the same direction. During this loop we check to see if anyone of the enemies has reached the edge of the screen. If this condition is true, then we move all of the enemies down, and switch the direction of their movement.
main.c
#include <stdlib.h>
#include <epoxy/gl.h>
#include <epoxy/glx.h>
#include <gtk/gtk.h>
#include "DashGL/dashgl.h"
static void on_realize(GtkGLArea *area);
static void on_render(GtkGLArea *area, GdkGLContext *context);
static gboolean on_idle(gpointer data);
static gboolean on_keydown(GtkWidget *widget, GdkEventKey *event);
static gboolean on_keyup(GtkWidget *widget, GdkEventKey *event);
#define WIDTH 640.0f
#define HEIGHT 480.0f
GLuint program;
GLuint vao;
GLint attribute_texcoord, attribute_coord2d;
GLint uniform_mytexture, uniform_mvp;
struct {
GLuint vbo;
GLuint tex;
mat4 mvp;
} background;
struct {
GLuint vbo;
GLuint tex;
vec3 pos;
mat4 mvp;
gboolean left;
gboolean right;
int num_bullets;
vec3 *bullets;
gboolean *active;
gboolean space;
} player;
struct {
GLuint vbo;
GLuint tex;
mat4 mvp;
GLfloat dy;
} bullet;
struct {
GLuint vbo;
GLuint tex;
mat4 mvp;
vec3 *pos;
int num_enemies;
float dx, dy;
} enemy;
int main(int argc, char *argv[]) {
GtkWidget *window;
GtkWidget *glArea;
gtk_init(&argc, &argv);
// Initialize Window
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(window), "Invaders Tutorial");
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_window_set_default_size(GTK_WINDOW(window), 640, 480);
gtk_window_set_type_hint(GTK_WINDOW(window), GDK_WINDOW_TYPE_HINT_UTILITY);
g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(window, "key-press-event", G_CALLBACK(on_keydown), NULL);
g_signal_connect(window, "key-release-event", G_CALLBACK(on_keyup), NULL);
// Initialize GTK GL Area
glArea = gtk_gl_area_new();
gtk_widget_set_vexpand(glArea, TRUE);
gtk_widget_set_hexpand(glArea, TRUE);
g_signal_connect(glArea, "realize", G_CALLBACK(on_realize), NULL);
g_signal_connect(glArea, "render", G_CALLBACK(on_render), NULL);
gtk_container_add(GTK_CONTAINER(window), glArea);
// Show widgets
gtk_widget_show_all(window);
gtk_main();
return 0;
}
static void on_realize(GtkGLArea *area) {
// Debug Message
g_print("on realize 0
");
gtk_gl_area_make_current(area);
if(gtk_gl_area_get_error(area) != NULL) {
fprintf(stderr, "Unknown error
");
return;
}
const GLubyte *renderer = glGetString(GL_RENDER);
const GLubyte *version = glGetString(GL_VERSION);
g_print("Renderer: %s
", renderer);
g_print("OpenGL version supported %s
", version);
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// Background Sprite
GLfloat background_vertices[] = {
0.0, 0.0, 0.0, 0.0,
0.0, HEIGHT, 0.0, 1.0,
WIDTH, HEIGHT, 1.0, 1.0,
0.0, 0.0, 0.0, 0.0,
WIDTH, HEIGHT, 1.0, 1.0,
WIDTH, 0.0, 1.0, 0.0
};
glGenBuffers(1, &background.vbo);
glBindBuffer(GL_ARRAY_BUFFER, background.vbo);
glBufferData(
GL_ARRAY_BUFFER,
sizeof(background_vertices),
background_vertices,
GL_STATIC_DRAW
);
mat4_identity(background.mvp);
background.tex = shader_load_texture("sprites/background.png");
// Player Sprite
GLfloat player_vertices[] = {
-22.0, -22.0, 0.0, 0.0,
-22.0, 22.0, 0.0, 1.0,
22.0, 22.0, 1.0, 1.0,
-22.0, -22.0, 0.0, 0.0,
22.0, 22.0, 1.0, 1.0,
22.0, -22.0, 1.0, 0.0
};
glGenBuffers(1, &player.vbo);
glBindBuffer(GL_ARRAY_BUFFER, player.vbo);
glBufferData(
GL_ARRAY_BUFFER,
sizeof(player_vertices),
player_vertices,
GL_STATIC_DRAW
);
player.pos[0] = WIDTH / 2;
player.pos[1] = 30.0f;
player.pos[2] = 0.0;
player.left = FALSE;
player.right = FALSE;
mat4_translate(player.pos, player.mvp);
player.tex = shader_load_texture("sprites/player.png");
player.space = FALSE;
player.num_bullets = 3;
player.bullets = malloc(player.num_bullets * sizeof(vec3));
player.active = malloc(player.num_bullets * sizeof(gboolean));
int i;
for(i = 0; i enemy.dx = 3.0f;
enemy.dy = -10.0f;
float x = 70.0f;
float y = HEIGHT - 140.0f;
for(i = 0; i
// Bullet Sprite
GLfloat bullet_vertices[] = {
-6.0, -12.0, 0.0, 0.0,
-6.0, 12.0, 0.0, 1.0,
6.0, 12.0, 1.0, 1.0,
-6.0, -12.0, 0.0, 0.0,
6.0, 12.0, 1.0, 1.0,
6.0, -12.0, 1.0, 0.0
};
glGenBuffers(1, &bullet.vbo);
glBindBuffer(GL_ARRAY_BUFFER, bullet.vbo);
glBufferData(
GL_ARRAY_BUFFER,
sizeof(bullet_vertices),
bullet_vertices,
GL_STATIC_DRAW
);
bullet.tex = shader_load_texture("sprites/bullet.png");
bullet.dy = 10.0f;
// Compile Shader Program
GLint compile_ok = GL_FALSE;
GLint link_ok = GL_FALSE;
const char *vs = "shader/vertex.glsl";
const char *fs = "shader/fragment.glsl";
program = shader_load_program(vs, fs);
const char *attribute_name = "coord2d";
attribute_coord2d = glGetAttribLocation(program, attribute_name);
if(attribute_coord2d == -1) {
fprintf(stderr, "Could not bind attribute %s
", attribute_name);
return;
}
attribute_name = "uv_coord";
attribute_texcoord = glGetAttribLocation(program, attribute_name);
if(attribute_texcoord == -1) {
fprintf(stderr, "Could not bind attribute %s
", attribute_name);
return;
}
const char *uniform_name = "orthograph";
GLint uniform_ortho = glGetUniformLocation(program, uniform_name);
if(uniform_ortho == -1) {
fprintf(stderr, "Could not bind uniform %s
", uniform_name);
return;
}
uniform_name = "mvp";
uniform_mvp = glGetUniformLocation(program, uniform_name);
if(uniform_mvp == -1) {
fprintf(stderr, "Could not bind uniform %s
", uniform_name);
return;
}
uniform_name = "mytexture";
uniform_mytexture = glGetUniformLocation(program, uniform_name);
if(uniform_mytexture == -1) {
fprintf(stderr, "Could not bind uniform %s
", uniform_name);
return;
}
glUseProgram(program);
mat4 orthograph;
mat4_orthagonal(WIDTH, HEIGHT, orthograph);
glUniformMatrix4fv(uniform_ortho, 1, GL_FALSE, orthograph);
g_timeout_add(20, on_idle, (void*)area);
}
static void on_render(GtkGLArea *area, GdkGLContext *context) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(program);
glBindVertexArray(vao);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, background.tex);
glUniform1i(uniform_mytexture, 0);
glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, background.mvp);
glEnableVertexAttribArray(attribute_coord2d);
glEnableVertexAttribArray(attribute_texcoord);
glBindBuffer(GL_ARRAY_BUFFER, background.vbo);
glVertexAttribPointer(
attribute_coord2d,
2,
GL_FLOAT,
GL_FALSE,
sizeof(float) * 4,
0
);
glVertexAttribPointer(
attribute_texcoord,
2,
GL_FLOAT,
GL_FALSE,
sizeof(float) * 4,
(void*)(sizeof(float) * 2)
);
glDrawArrays(GL_TRIANGLES, 0, 6);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, player.tex);
glUniform1i(uniform_mytexture, 0);
mat4_translate(player.pos, player.mvp);
glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, player.mvp);
glBindBuffer(GL_ARRAY_BUFFER, player.vbo);
glVertexAttribPointer(
attribute_coord2d,
2,
GL_FLOAT,
GL_FALSE,
sizeof(float) * 4,
0
);
glVertexAttribPointer(
attribute_texcoord,
2,
GL_FLOAT,
GL_FALSE,
sizeof(float) * 4,
(void*)(sizeof(float) * 2)
);
glDrawArrays(GL_TRIANGLES, 0, 6);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, bullet.tex);
glUniform1i(uniform_mytexture, 0);
int i;
for(i = 0; i WIDTH) {
player.pos[0] = WIDTH;
}
int i;
for(i = 0; i gboolean do_switch = FALSE;
for(i = 0; i WIDTH || enemy.pos[i][0] <0) {
do_switch = TRUE;
}
}
if(do_switch) {
enemy.dx = -enemy.dx;
for(i = 0; i
gtk_widget_queue_draw(GTK_WIDGET(data));
return TRUE;
}
static gboolean on_keydown(GtkWidget *widget, GdkEventKey *event) {
switch(event->keyval) {
case GDK_KEY_Left:
player.left = TRUE;
break;
case GDK_KEY_Right:
player.right = TRUE;
break;
case GDK_KEY_space:
if(!player.space) {
int i;
for(i = 0; i keyval) {
case GDK_KEY_Left:
player.left = FALSE;
break;
case GDK_KEY_Right:
player.right = FALSE;
break;
case GDK_KEY_space:
player.space = FALSE;
break;
}
}
Compile
$ gcc -c -o DashGL/dashgl.o DashGL/dashgl.c -lepoxy -lpng -lm
$ gcc `pkg-config --cflags gtk+-3.0` main.c DashGL/dashgl.o `pkg-config --libs gtk+-3.0` \
-lepoxy -lm -lpngRun
$ ./a.out