I'm making sheep that wander automatically: they should remain idle for a while, then randomly choose either LEFT or RIGHT and move in that direction for a set amount of time before becoming idle again. My current code calls sheep_mvmt every frame, and that function calls rand() each time, so the direction is regenerated on every frame instead of being selected once and preserved. How should I structure the state and timing logic so the random direction is chosen only when the sheep leaves IDLE?
3 Answers
Your enum values are typically `IDLE = 0`, `LEFT = 1`, and `RIGHT = 2`, so `(rand() % 2) + 1` does produce LEFT or RIGHT. However, a clearer and safer expression is `sheep1.state = (rand() % 2 == 0) ? LEFT : RIGHT;`. Also seed the random generator once during setup, as you already do; do not reseed it inside the game loop.
Right now `sheep_mvmt()` is called every frame, so `STATE pick = ...` keeps replacing the direction roughly 60 times per second. Random selection and movement are separate actions: select a state once, save it in the sheep, and have the update code use that saved state until the movement interval ends. A pointer is not needed for this; assigning directly to `sheep1.state` is enough.
Choose the direction when the sheep changes from IDLE to moving, then store that value in sheep1.state. The movement function should only move according to the already-selected state and should not call rand(). For example: `if (sheep_counter >= 120 && sheep1.state == IDLE) { sheep1.state = (rand() % 2) ? LEFT : RIGHT; sheep_counter = 0; } else if (sheep1.state != IDLE) { if (sheep1.state == RIGHT) sheep1.position.x += sheep1.velocity * dt; else if (sheep1.state == LEFT) sheep1.position.x -= sheep1.velocity * dt; if (sheep_counter >= 240) { sheep1.state = IDLE; sheep_counter = 0; } }`. The important part is that `rand()` runs during the IDLE-to-moving transition, not once per frame.
You can also base the timing on elapsed seconds instead of counting frames. Increment a timer with `dt`, choose a direction when the timer reaches the idle duration, and return to IDLE when it reaches the movement duration. That works consistently even if the frame rate changes.