Tutorials

Tutorials for getting started with programming on Linux

Draw Static Enemy

Gtk Invaders

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Similar to the way we drew a static bullet before attempting to animate it, we will draw a static enemy, and then add to it.

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; } 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 GLfloat enemy_vertices[] = { -32.0, -32.0, 0.0, 0.0, -32.0, 32.0, 0.0, 1.0, 32.0, 32.0, 1.0, 1.0, -32.0, -32.0, 0.0, 0.0, 32.0, 32.0, 1.0, 1.0, 32.0, -32.0, 1.0, 0.0 }; glGenBuffers(1, &enemy.vbo); glBindBuffer(GL_ARRAY_BUFFER, enemy.vbo); glBufferData( GL_ARRAY_BUFFER, sizeof(enemy_vertices), enemy_vertices, GL_STATIC_DRAW ); enemy.tex = shader_load_texture("sprites/enemy.png"); enemy.pos[0] = WIDTH / 2.0f; enemy.pos[1] = HEIGHT / 2.0f; enemy.pos[2] = 0.0f; // 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 glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, enemy.tex); glUniform1i(uniform_mytexture, 0); mat4_translate(enemy.pos, enemy.mvp); glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, enemy.mvp); glBindBuffer(GL_ARRAY_BUFFER, enemy.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); glDisableVertexAttribArray(attribute_coord2d); glDisableVertexAttribArray(attribute_texcoord); } static gboolean on_idle(gpointer data) { if(player.right) { player.pos[0] += 6.0f; } if(player.left) { player.pos[0] -= 6.0f; } if(player.pos[0] <0) { player.pos[0] = 0.0f; } else if(player.pos[0] > WIDTH) { player.pos[0] = WIDTH; } int i; for(i = 0; i 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 -lpng

Run

$ ./a.out