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More of the 2D engine. Bullets.
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@antirez
antirez committed Jan 5, 2023
1 parent f3b9322 commit 6dbb606
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Showing 2 changed files with 165 additions and 52 deletions.
215 changes: 164 additions & 51 deletions app.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,28 @@
#define PI 3.14159265358979f
#endif

/* ============================ Data structures ============================= */

typedef struct Ship {
float x, /* Ship x position. */
y, /* Ship y position. */
vx, /* x velocity. */
vy, /* y velocity. */
rot; /* Current rotation. 2*PI full ortation. */
} Ship;

typedef struct Bullet {
float x, y, vx, vy; /* Fields like in ship. */
uint32_t ttl; /* Time to live, in ticks. */
} Bullet;

typedef struct Asteroid {
float x, y, vx, vy, /* Fields like ship. */
rot_speed, /* Angular velocity (rot speed and sense). */
size; /* Asteroid size. */
uint8_t shape_seed; /* Seed to give random shape. */
} Asteroid;

#define MAXBUL 10 /* Max bullets on the screen. */
#define MAXAST 8 /* Max asteroids on the screen. */
typedef struct AsteroidsApp {
Expand All @@ -33,27 +55,15 @@ typedef struct AsteroidsApp {
uint32_t ticks; /* Game ticks. Increments at each refresh. */

/* Ship state. */
struct {
float x, /* Ship x position. */
y, /* Ship y position. */
vx, /* x velocity. */
vy, /* y velocity. */
rot; /* Current rotation. 2*PI full ortation. */
} ship;
struct Ship ship;

/* Bullets state. */
struct {
float x, y, vx, vy; /* Fields like in ship. */
} bullets[MAXBUL];
struct Bullet bullets[MAXBUL]; /* Each bullet state. */
int bullets_num; /* Active bullets. */
uint32_t last_bullet_tick; /* Tick the last bullet was fired. */

/* Asteroids state. */
struct {
float x, y, vx, vy, rot, /* Fields like ship. */
size; /* Asteroid size. */
uint8_t shape_seed; /* Seed to give random shape. */
} asteroids[MAXAST]; /* Asteroids state. */
Asteroid asteroids[MAXAST]; /* Each asteroid state. */
int asteroids_num; /* Active asteroids. */

uint32_t pressed[InputKeyMAX]; /* pressed[id] is true if pressed.
Expand All @@ -62,6 +72,8 @@ typedef struct AsteroidsApp {
bool fire; /* Short press detected: fire a bullet. */
} AsteroidsApp;

/* ============================ 2D drawing ================================== */

/* This structure represents a polygon of at most POLY_MAX points.
* The function draw_poly() is able to render it on the screen, rotated
* by the amount specified. */
Expand Down Expand Up @@ -94,16 +106,14 @@ void rotate_poly(Poly *rot, Poly *poly, float a) {
rot->points = poly->points;
}

#if 0
/* This is an 8 bit LFSR we use to generate a predictable and fast
* pseudorandom sequence of numbers, to give a different shape to
* each asteroid. */
static void lfsr_next(unsigned char *prev) {
void lfsr_next(unsigned char *prev) {
unsigned char lsb = *prev & 1;
*prev = *prev >> 1;
if (lsb == 1) *prev ^= 0b11000111;
}
#endif

/* Render the polygon 'poly' at x,y, rotated by the specified angle. */
void draw_poly(Canvas *const canvas, Poly *poly, uint8_t x, uint8_t y, float a)
Expand All @@ -120,21 +130,153 @@ void draw_poly(Canvas *const canvas, Poly *poly, uint8_t x, uint8_t y, float a)
}
}

/* A bullet is just a + pixels pattern. A single pixel is not
* visible enough. */
void draw_bullet(Canvas *const canvas, uint8_t x, uint8_t y) {
canvas_draw_dot(canvas,x-1,y);
canvas_draw_dot(canvas,x+1,y);
canvas_draw_dot(canvas,x,y);
canvas_draw_dot(canvas,x,y-1);
canvas_draw_dot(canvas,x,y+1);
}

/* Given the current position, update it according to the velocity and
* wrap it back to the other side if the object went over the screen. */
void update_pos_by_velocity(float *x, float *y, float vx, float vy) {
/* Return back from one side to the other of the screen. */
*x += vx;
*y += vy;
if (*x >= SCREEN_XRES) *x = 0;
else if (*x < 0) *x = SCREEN_XRES-1;
if (*y >= SCREEN_YRES) *y = 0;
else if (*y < 0) *y = SCREEN_YRES-1;
}

/* Render the current game screen. */
static void render_callback(Canvas *const canvas, void *ctx) {
void render_callback(Canvas *const canvas, void *ctx) {
AsteroidsApp *app = ctx;

/* Clear screen. */
canvas_set_color(canvas, ColorWhite);
canvas_draw_box(canvas, 0, 0, 127, 63);

/* Draw ship and asteroids. */
/* Draw ship, asteroids, bullets. */
draw_poly(canvas,&ShipPoly,app->ship.x,app->ship.y,app->ship.rot);

for (int j = 0; j < app->bullets_num; j++)
draw_bullet(canvas,app->bullets[j].x,app->bullets[j].y);
}

/* ============================ Game logic ================================== */

float distance(float x1, float y1, float x2, float y2) {
float dx = x1-x2;
float dy = y1-y2;
return sqrt(dx*dx+dy*dy);
}

/* Create a new bullet headed in the same direction of the ship. */
void ship_fire_bullet(AsteroidsApp *app) {
if (app->bullets_num == MAXBUL) return;
Bullet *b = &app->bullets[app->bullets_num];
b->x = app->ship.x;
b->y = app->ship.y;
b->vx = -sin(app->ship.rot);
b->vy = cos(app->ship.rot);

/* Ship should fire from its head, not in the middle. */
b->x += b->vx*5;
b->y += b->vy*5;

/* It's more realistic if we add the velocity vector of the
* ship, too. Otherwise if the ship is going fast the bullets
* will be slower, which is not how the world works. */
b->vx += app->ship.vx;
b->vy += app->ship.vy;

b->ttl = 50; /* The bullet will disappear after N ticks. */
app->bullets_num++;
}

/* Remove the specified bullet by id (index in the array). */
void remove_bullet(AsteroidsApp *app, int bid) {
/* Replace the top bullet with the empty space left
* by the removal of this bullet. This way we always take the
* array dense, which is an advantage when looping. */
int n = --app->bullets_num;
if (n && bid != n) app->bullets[bid] = app->bullets[n];
}

/* Create a new asteroid, away from the ship. */
void add_asteroid(AsteroidsApp *app) {
if (app->asteroids_num == MAXAST) return;
float size = 4+rand()%15;
float min_distance = 20;
float x,y;
do {
x = rand() % SCREEN_XRES;
y = rand() % SCREEN_YRES;
} while(distance(app->ship.x,app->ship.y,x,y) < min_distance+size);
Asteroid *a = &app->asteroids[app->asteroids_num++];
a->x = x;
a->y = y;
a->vx = (rand()/RAND_MAX)*2;
a->vy = (rand()/RAND_MAX)*2;
a->size = size;
a->rot_speed = (rand()/RAND_MAX)/10;
if (app->ticks & 1) a->rot_speed = -(a->rot_speed);
a->shape_seed = (app->ticks * 1337) & 255;
}

/* This is the main game execution function, called 10 times for
* second (with the Flipper screen latency, an higher FPS does not
* make sense). In this function we update the position of objects based
* on velocity. Detect collisions. Update the score and so forth.
*
* Each time this function is called, app->tick is incremented. */
void game_tick(void *ctx) {
AsteroidsApp *app = ctx;
if (app->pressed[InputKeyLeft]) app->ship.rot -= .2;
if (app->pressed[InputKeyRight]) app->ship.rot += .2;
if (app->pressed[InputKeyOk]) {
app->ship.vx -= 0.15*(float)sin(app->ship.rot);
app->ship.vy += 0.15*(float)cos(app->ship.rot);
}

/* Update ship position according to its velocity. */
update_pos_by_velocity(&app->ship.x,&app->ship.y,app->ship.vx,app->ship.vy);

/* Update bullets position. */
for (int j = 0; j < app->bullets_num; j++) {
update_pos_by_velocity(&app->bullets[j].x,&app->bullets[j].y,
app->bullets[j].vx,app->bullets[j].vy);
if (--app->bullets[j].ttl == 0) {
remove_bullet(app,j);
j--; /* Process this bullet index again: the removal will
fill it with the top bullet to take the array dense. */
}
}

/* Fire a bullet if needed. */
if (app->fire) {
ship_fire_bullet(app);
app->fire = false;
}

/* From time to time, create a new asteroid. The more asteroids
* already on the screen, the smaller probability of creating
* a new one. */
if ((random() & 255) < (30/app->asteroids_num)) add_asteroid(app);

app->ticks++;
view_port_update(app->view_port);
}

/* ======================== Flipper specific code =========================== */

/* Here all we do is putting the events into the queue that will be handled
* in the while() loop of the app entry point function. */
static void input_callback(InputEvent* input_event, void* ctx)
void input_callback(InputEvent* input_event, void* ctx)
{
AsteroidsApp *app = ctx;
furi_message_queue_put(app->event_queue,input_event,FuriWaitForever);
Expand Down Expand Up @@ -183,43 +325,14 @@ void asteroids_app_free(AsteroidsApp *app) {
free(app);
}

/* Thi is the main game execution function, called 10 times for
* second (with the Flipper screen latency, an higher FPS does not
* make sense). In this function we update the position of objects based
* on velocity. Detect collisions. Update the score and so forth.
*
* Each time this function is called, app->tick is incremented. */
static void game_tick(void *ctx) {
AsteroidsApp *app = ctx;
if (app->pressed[InputKeyLeft]) app->ship.rot -= .2;
if (app->pressed[InputKeyRight]) app->ship.rot += .2;
if (app->pressed[InputKeyOk]) {
app->ship.vx -= 0.15*(float)sin(app->ship.rot);
app->ship.vy += 0.15*(float)cos(app->ship.rot);
}

/* Update ship position according to its velocity. */
app->ship.x += app->ship.vx;
app->ship.y += app->ship.vy;

/* Return back from one side to the other of the screen. */
if (app->ship.x >= SCREEN_XRES) app->ship.x = 0;
else if (app->ship.x < 0) app->ship.x = SCREEN_XRES-1;
if (app->ship.y >= SCREEN_YRES) app->ship.y = 0;
else if (app->ship.y < 0) app->ship.y = SCREEN_YRES-1;

app->ticks++;
view_port_update(app->view_port);
}

/* Handle keys interaction. */
void asteroids_update_keypress_state(AsteroidsApp *app, InputEvent input) {
if (input.type == InputTypePress) {
app->pressed[input.key] = furi_get_tick();
} else if (input.type == InputTypeRelease) {
uint32_t dur = furi_get_tick() - app->pressed[input.key];
app->pressed[input.key] = 0;
if (dur < 100 && input.key == InputKeyOk) app->fire = true;
if (dur < 200 && input.key == InputKeyOk) app->fire = true;
}
}

Expand Down
2 changes: 1 addition & 1 deletion application.fam
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
App(
appid="protoview",
appid="asteroids",
name="Asteroids",
apptype=FlipperAppType.EXTERNAL,
entry_point="asteroids_app_entry",
Expand Down

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