Shoot Player Bullets
Gtk Invaders
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For our player, we will set a specific number of bullet which they are able to shoot. Each bullet will be active while it is on the screen and will deactive if it comes in contact with an enemy or goes off the screen. When the player presses a button, we iterate over the list of bullets. If all bullets are active, no bullet will be fired. Otherwise, we will set the bullet positon to that of the player, and activate the bullet.
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;
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
// 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
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
}
}
static gboolean on_keyup(GtkWidget *widget, GdkEventKey *event) {
switch(event->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