Draw Edge Sprites
Simple Astroids clone
Published
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In the previous step, we wrapped the player sprite to the viewport, but the effect was less than convincing. In this step we add a check to see if the player sprite is close to the edge of the screen. If it is, then we will draw the sprite twice.
main.c
#include <epoxy/gl.h>
#include <epoxy/glx.h>
#include <gtk/gtk.h>
#include <math.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;
vec3 pos;
mat4 mvp;
gboolean left;
gboolean right;
gboolean up;
GLfloat rot;
GLfloat dx, dy, max;
} player;
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), "Astroids 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);
printf("Renderer: %s\n", renderer);
printf("OpenGL version supported %s\n", version);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
GLfloat player_vertices[] = {
-24.0, -24.0, 0.0, 0.0,
-24.0, 24.0, 0.0, 1.0,
24.0, 24.0, 1.0, 1.0,
-24.0, -24.0, 0.0, 0.0,
24.0, 24.0, 1.0, 1.0,
24.0, -24.0, 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 / 2.0f;
player.pos[1] = HEIGHT / 2.0f;
player.pos[2] = 0.0;
player.left = FALSE;
player.right = FALSE;
player.up = FALSE;
mat4_translate(player.pos, player.mvp);
player.tex = shader_load_texture("sprites/player.png");
player.dx = 0.0f;
player.dy = 0.0f;
player.max = 8.0f;
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;
}
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) {
gboolean draw_mirror = FALSE;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(program);
glBindVertexArray(vao);
glEnableVertexAttribArray(attribute_coord2d);
glEnableVertexAttribArray(attribute_texcoord);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, player.tex);
glUniform1i(uniform_mytexture, 0);
mat4 pos, rot;
mat4_translate(player.pos, pos);
mat4_rotate_z(player.rot, rot);
mat4_multiply(pos, rot, 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);
if(player.pos[0] > WIDTH - 24.0f) {
player.pos[0] -= WIDTH;
draw_mirror = TRUE;
} else if(player.pos[0] <24.0f) {
player.pos[0] += WIDTH;
draw_mirror = TRUE;
}
if(player.pos[1] > HEIGHT - 24.0f) {
player.pos[1] -= HEIGHT;
draw_mirror = TRUE;
} else if(player.pos[1] <24.0f) {
player.pos[1] += HEIGHT;
draw_mirror = TRUE;
}
if(draw_mirror) {
mat4_translate(player.pos, pos);
mat4_rotate_z(player.rot, rot);
mat4_multiply(pos, rot, 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);
}
glDisableVertexAttribArray(attribute_coord2d);
glDisableVertexAttribArray(attribute_texcoord);
}
static gboolean on_idle(gpointer data) {
if(player.right) {
player.rot -= 0.05f;
}
if(player.left) {
player.rot += 0.05f;
}
float dx, dy;
if(player.up) {
player.dx -= sin(player.rot) * 0.05;
player.dy += cos(player.rot) * 0.05;
}
if(player.dx <-player.max) {
player.dx = -player.max;
} else if(player.dx > player.max) {
player.dx = player.max;
}
if(player.dy <-player.max) {
player.dy = -player.max;
} else if(player.dy > player.max) {
player.dy = player.max;
}
player.pos[0] += player.dx;
player.pos[1] += player.dy;
/*
if(player.pos[0] > WIDTH) {
player.pos[0] -= WIDTH;
} else if(player.pos[0] <0) {
player.pos[0] += WIDTH;
}
if(player.pos[1] > HEIGHT) {
player.pos[1] -= HEIGHT;
} else if(player.pos[1] <0) {
player.pos[1] += HEIGHT;
}
*/
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_Up:
player.up = TRUE;
break;
}
}
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_Up:
player.up = 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