5-utils.cpp

// Check collision between two boxes (http://lazyfoo.net/tutorials/SDL/27_collision_detection/index.php)
bool collision(float xA, float xB, float yA, float yB, int wA, int wB, int hA, int hB) {
    if (yA + hA <= yB) {
        return false;
    }

    if (yA >= yB + hB) {
        return false;
    }

    if (xA + wA <= xB) {
        return false;
    }

    if (xA >= xB + wB) {
        return false;
    }

    return true;
}

// Given a bullet, check if it hits a zombie
void hitZombies(struct Bullet *bullet) {

    for (int i = 0; i < ZOMBIE_COUNT; i++) {  // For each zombie..
         
        // If the bullet and the zombie collide..
        if (zombies[i].alive && collision(bullet->x, zombies[i].x, bullet->y, zombies[i].y, bullet->w, zombies[i].w, bullet->h, zombies[i].h)) {
            zombies[i].vX = bullet->dir * 10;   // Apply horizontal impulse
            zombies[i].state = "state_hit";     // Zombie is now hit
            bullet->alive = false;              // Destroy bullet
        }
    }
}

// Check if the survivor has stabbed a zombie
void stabZombies() {

    for (int i = 0; i < ZOMBIE_COUNT; i++) {
        
        // If zombies is alive and it collides with the survivor..
        if (zombies[i].alive && collision(survivor.x, zombies[i].x, survivor.y, zombies[i].y, survivor.w, zombies[i].w, survivor.h, zombies[i].h)) {
            zombies[i].vY = -15;                  // Apply a vertical impulse
            zombies[i].vX = survivor.scaleX * 5;  // Apply a horizontal impulse (wrt the survivor facing)
            zombies[i].state = "state_hit";       // Zombie is now hit
        }
    }
}