Tutorials

Tutorials for getting started with programming on Linux

Draw Row of Bricks

We add a single row of bricks in order to draw and array of objects

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Next, we need some bricks to break. We start simple with a single row, we’ll fill out the rest of the grid in the next step.

main.c
#include <epoxy/gl.h> #include <epoxy/glx.h> #include <gtk/gtk.h> #include <math.h> #include "DashGL/dashgl.h" #define WIDTH 640.0f #define HEIGHT 480.0f 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); struct { float dx, dy; float r; vec3 pos; vec3 color; mat4 mvp; GLuint vbo; gboolean left, right, top, bottom; } ball; struct { float width; float height; float dx; vec3 pos; vec3 color; mat4 mvp; GLuint vbo; gboolean key_left; gboolean key_right; } paddle; struct bricks { float width; float height; mat4 mvp[6]; vec3 pos[6]; vec3 color; GLuint vbo; } bricks; GLuint program; GLuint vao; GLint attribute_coord2d; GLint uniform_mvp, uniform_color; 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), "Brickout 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\n"); gtk_gl_area_make_current(area); if(gtk_gl_area_get_error(area) != NULL) { fprintf(stderr, "Unknown error\n"); return; } const GLubyte *renderer = glGetString(GL_RENDER); const GLubyte *version = glGetString(GL_VERSION); const GLubyte *shader = glGetString(GL_SHADING_LANGUAGE_VERSION); printf("Shader %s\n", shader); printf("Renderer: %s\n", renderer); printf("OpenGL version supported %s\n", version); glClearColor(1.0f, 1.0f, 1.0f, 1.0f); glGenVertexArrays(1, &vao); glBindVertexArray(vao); ball.r = 18.0f; int i; float angle, nextAngle; int num_segments = 99; GLfloat circle_vertices[6 * 100]; for(i = 0; i bricks.width = 51.0f; bricks.height = 13.0f; GLfloat bricks_vertices[] = { -bricks.width, -bricks.height, -bricks.width, bricks.height, bricks.width, bricks.height, bricks.width, bricks.height, bricks.width, -bricks.height, -bricks.width, -bricks.height }; glGenBuffers(1, &bricks.vbo); glBindBuffer(GL_ARRAY_BUFFER, bricks.vbo); glBufferData( GL_ARRAY_BUFFER, sizeof(bricks_vertices), bricks_vertices, GL_STATIC_DRAW ); 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\n", 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\n", uniform_name); return; } uniform_name = "mvp"; uniform_mvp = glGetUniformLocation(program, uniform_name); if(uniform_mvp == -1) { fprintf(stderr, "Could not bind uniform %s\n", uniform_name); return; } uniform_name = "color"; uniform_color = glGetUniformLocation(program, uniform_name); if(uniform_color == -1) { fprintf(stderr, "Could not bind uniform %s\n", 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); ball.dx = 2.0f; ball.dy = 3.0f; ball.pos[0] = 50.0f; ball.pos[1] = 50.0f; ball.pos[2] = 0.0f; ball.color[0] = 0.0f; ball.color[1] = 0.0f; ball.color[2] = 1.0f; paddle.dx = 2.0f; paddle.pos[0] = WIDTH / 2.0f; paddle.pos[1] = 20.0f; paddle.pos[2] = 0.0f; paddle.color[0] = 0.0f; paddle.color[1] = 0.0f; paddle.color[2] = 0.0f; bricks.color[0] = 1.0f; bricks.color[1] = 0.0f; bricks.color[2] = 0.0f; vec3 pos; for(i = 0; i <6; i++) { bricks.pos[i][0] = (4.0f + bricks.width) * (1 + i) + bricks.width * i; bricks.pos[i][1] = HEIGHT - (4.0f + bricks.height); bricks.pos[i][2] = 0.0f; mat4_translate(bricks.pos[i], bricks.mvp[i]); } } static void on_render(GtkGLArea *area, GdkGLContext *context) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); mat4_translate(ball.pos, ball.mvp); glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, ball.mvp); glUniform3fv(uniform_color, 1, ball.color); glBindVertexArray(vao); glEnableVertexAttribArray(attribute_coord2d); glBindBuffer(GL_ARRAY_BUFFER, ball.vbo); glVertexAttribPointer( attribute_coord2d, 2, GL_FLOAT, GL_FALSE, 0, 0 ); glDrawArrays(GL_TRIANGLES, 0, 3 * 100); mat4_translate(paddle.pos, paddle.mvp); glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, paddle.mvp); glUniform3fv(uniform_color, 1, paddle.color); glBindBuffer(GL_ARRAY_BUFFER, paddle.vbo); glVertexAttribPointer( attribute_coord2d, 2, GL_FLOAT, GL_FALSE, 0, 0 ); glDrawArrays(GL_TRIANGLES, 0, 3 * 2); glUniform3fv(uniform_color, 1, bricks.color); glBindBuffer(GL_ARRAY_BUFFER, bricks.vbo); glVertexAttribPointer( attribute_coord2d, 2, GL_FLOAT, GL_FALSE, 0, 0 ); int i; for(i = 0; i <6; i++) { glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, bricks.mvp[i]); glDrawArrays(GL_TRIANGLES, 0, 3 * 2); } glDisableVertexAttribArray(attribute_coord2d); } static gboolean on_idle(gpointer data) { ball.pos[0] += ball.dx; ball.pos[1] += ball.dy; if(ball.pos[0] > WIDTH) { ball.pos[0] = WIDTH; ball.dx *= -1; } else if(ball.pos[0] <0) { ball.pos[0] = 0; ball.dx *= -1; } if(ball.pos[1] > HEIGHT) { ball.pos[1] = HEIGHT; ball.dy *= -1; } else if(ball.pos[1] <0) { ball.pos[1] = 0; ball.dy *= -1; } if(paddle.key_left) { paddle.pos[0] -= paddle.dx; } if(paddle.key_right) { paddle.pos[0] += paddle.dx; } if(paddle.pos[0] <0) { paddle.pos[0] = 0.0f; } else if(paddle.pos[0] > WIDTH) { paddle.pos[0] = WIDTH; } ball.left = ball.pos[0] > paddle.pos[0] - paddle.width; ball.right = ball.pos[0] paddle.pos[1] - paddle.height; if(ball.dy <0 && ball.left && ball.right && ball.top && ball.bottom) { ball.dy *= -1.05; } gtk_widget_queue_draw(GTK_WIDGET(data)); return TRUE; } static gboolean on_keydown(GtkWidget *widget, GdkEventKey *event) { switch(event->keyval) { case GDK_KEY_Left: paddle.key_left = TRUE; break; case GDK_KEY_Right: paddle.key_right = TRUE; break; } } static gboolean on_keyup(GtkWidget *widget, GdkEventKey *event) { switch(event->keyval) { case GDK_KEY_Left: paddle.key_left = FALSE; break; case GDK_KEY_Right: paddle.key_right = 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