Johnny Fernandes
234 lines
9.2 KiB
Python
234 lines
9.2 KiB
Python
"""
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Sheep flocking controller (Webots, Reynolds boids variant).
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Each sheep broadcasts its GPS position every 3 steps on channel 1 and
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listens for the dog and peer sheep positions. Peers are keyed by robot
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name so each neighbour has exactly one current entry in the dict.
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Force stack each step (summed then converted to a heading + speed):
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flee — away from dog, quadratic ramp, dominant when close
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cohesion — toward flock centre, halved while fleeing
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separation — inverse-distance push, prevents physical overlap
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walls — linear repulsion from field boundary
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wander — small persistent drift for natural idle motion
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Pen behaviour: on first entry into the quarantine pen the sheep latches
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permanently — it turns pink (via the exposed woolColor PROTO field) and
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the normal force stack is replaced by pen-confinement forces only.
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"""
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import random
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import math
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from controller import Supervisor
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# ---------------------------------------------------------------------------
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# Tuning constants
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# ---------------------------------------------------------------------------
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MAX_SPEED = 22.0 # rad/s hard clamp on both motors
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FLEE_SPEED = 20.0 # rad/s upper bound while panicking
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WANDER_SPEED = 3.0 # rad/s lower bound during calm wandering
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X_MIN, X_MAX = -14.5, 14.5 # stone wall inner edges (metres)
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Y_MIN, Y_MAX = -14.5, 14.5
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WALL_MARGIN = 3.5 # avoidance starts this far from the wall
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FLEE_DIST = 7.0 # dog within this radius triggers flee (metres)
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SEPARATION_DIST = 2.5 # inverse-distance push active inside this radius
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COHESION_DIST = 8.0 # pull toward flock centre active inside this radius
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PEN_X_MIN, PEN_X_MAX = 10.0, 13.0 # quarantine pen extents (metres)
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PEN_Y_MIN, PEN_Y_MAX = -15.0, -8.0 # open entrance at y=-8, gate at y=-15
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PEN_MARGIN = 0.8 # confinement force starts this far from pen wall
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# ---------------------------------------------------------------------------
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# Device setup
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# ---------------------------------------------------------------------------
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robot = Supervisor()
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timestep = int(robot.getBasicTimeStep())
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name = robot.getName()
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self_node = robot.getSelf()
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left_motor = robot.getDevice("left wheel motor")
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right_motor = robot.getDevice("right wheel motor")
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left_motor.setPosition(float("inf"))
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right_motor.setPosition(float("inf"))
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left_motor.setVelocity(0.0)
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right_motor.setVelocity(0.0)
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gps = robot.getDevice("gps"); gps.enable(timestep)
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compass = robot.getDevice("compass"); compass.enable(timestep)
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receiver = robot.getDevice("receiver"); receiver.enable(timestep)
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emitter = robot.getDevice("emitter")
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# ---------------------------------------------------------------------------
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# Helpers
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# ---------------------------------------------------------------------------
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def norm_angle(a):
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return math.atan2(math.sin(a), math.cos(a))
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def bearing():
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# Compass returns north direction in sensor frame; for this Z-up world
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# with north = +Y, atan2(n[0], n[1]) gives the standard math angle
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# (0 = east, π/2 = north) matching atan2(fy, fx) used for heading.
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n = compass.getValues()
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return math.atan2(n[0], n[1])
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def drive(heading, speed):
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err = norm_angle(heading - bearing())
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# Scale forward component by cos(err): at 90° error fwd→0 so the robot
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# spins in place to realign rather than driving sideways at full speed.
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fwd = speed * max(0.0, math.cos(err))
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k = 4.0
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left_motor.setVelocity( max(-MAX_SPEED, min(MAX_SPEED, fwd - k * err)))
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right_motor.setVelocity(max(-MAX_SPEED, min(MAX_SPEED, fwd + k * err)))
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def paint_pink():
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# woolColor is declared as a PROTO field with IS binding to the DEF WOOL
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# PBRAppearance baseColor. Changing it here propagates to every USE WOOL
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# shape on the body. Direct field access avoids PROTO-internal opacity.
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self_node.getField("woolColor").setSFColor([1.0, 0.55, 0.72])
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# ---------------------------------------------------------------------------
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# State
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# ---------------------------------------------------------------------------
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wander_angle = random.uniform(-math.pi, math.pi)
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step = 0
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dog_x = None
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dog_y = None
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peers = {} # name → (x, y), one entry per neighbour, cleared every 30 steps
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penned = False
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# ---------------------------------------------------------------------------
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# Main loop
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# ---------------------------------------------------------------------------
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while robot.step(timestep) != -1:
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step += 1
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pos = gps.getValues()
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x, y = pos[0], pos[1]
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# Pen entry: one-way latch, never unset
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if not penned and PEN_X_MIN < x < PEN_X_MAX and PEN_Y_MIN < y < PEN_Y_MAX:
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penned = True
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paint_pink()
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# Refresh peer table (clear before receiving so fresh data is never lost)
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if step % 30 == 0:
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peers.clear()
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while receiver.getQueueLength() > 0:
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msg = receiver.getString()
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receiver.nextPacket()
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p = msg.split(":")
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if p[0] == "dog" and len(p) >= 3:
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dog_x, dog_y = float(p[1]), float(p[2])
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elif p[0] == "sheep" and len(p) >= 4 and p[1] != name:
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peers[p[1]] = (float(p[2]), float(p[3]))
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fx, fy = 0.0, 0.0
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# Repel unpenned sheep from the exterior of the pen's side walls so they
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# don't get pinned by flee forces. Only fires when strictly outside the pen
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# (x < PEN_X_MIN or x > PEN_X_MAX) at pen height (y in pen y-range).
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# Entrance is open on the north (y > PEN_Y_MAX) — no force there.
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PEN_EXT_MARGIN = 0.8
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if not penned and PEN_Y_MIN < y < PEN_Y_MAX:
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if PEN_X_MIN - PEN_EXT_MARGIN < x < PEN_X_MIN:
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fx -= ((x - (PEN_X_MIN - PEN_EXT_MARGIN)) / PEN_EXT_MARGIN) * 6.0
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if PEN_X_MAX < x < PEN_X_MAX + PEN_EXT_MARGIN:
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fx += ((PEN_X_MAX + PEN_EXT_MARGIN - x) / PEN_EXT_MARGIN) * 6.0
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if penned:
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# Inside pen: wander freely, strong boundary forces prevent exit,
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# separation still active to avoid collisions with other penned sheep.
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pm = PEN_MARGIN
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if x < PEN_X_MIN + pm: fx += ((PEN_X_MIN + pm - x) / pm) * 15.0
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if x > PEN_X_MAX - pm: fx -= ((x - (PEN_X_MAX - pm)) / pm) * 15.0
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if y < PEN_Y_MIN + pm: fy += ((PEN_Y_MIN + pm - y) / pm) * 15.0
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if y > PEN_Y_MAX - pm: fy -= ((y - (PEN_Y_MAX - pm)) / pm) * 15.0
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for px, py in peers.values():
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dx, dy = px - x, py - y
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d = math.hypot(dx, dy)
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if 0.05 < d < SEPARATION_DIST:
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push = (SEPARATION_DIST - d) / d
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fx -= (dx / d) * push * 2.5
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fy -= (dy / d) * push * 2.5
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if random.random() < 0.02:
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wander_angle += random.uniform(-0.6, 0.6)
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fx += math.cos(wander_angle) * 0.5
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fy += math.sin(wander_angle) * 0.5
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else:
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fleeing = False
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# Flee — quadratic ramp so force grows rapidly as the dog closes in
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if dog_x is not None:
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dx = dog_x - x
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dy = dog_y - y
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dist = math.hypot(dx, dy)
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if 0.01 < dist < FLEE_DIST:
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fleeing = True
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t = 1.0 - dist / FLEE_DIST
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s = t * t * 20.0
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fx -= (dx / dist) * s
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fy -= (dy / dist) * s
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# Cohesion — halved while fleeing to reduce mid-panic collisions
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cx, cy, cn = 0.0, 0.0, 0
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for px, py in peers.values():
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d = math.hypot(px - x, py - y)
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if 0.3 < d < COHESION_DIST:
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cx += px; cy += py; cn += 1
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if cn > 0:
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w = 0.08 if fleeing else 0.15
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fx += (cx / cn - x) * w
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fy += (cy / cn - y) * w
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# Separation — inverse-distance: huge when nearly overlapping, fades quickly
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for px, py in peers.values():
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dx, dy = px - x, py - y
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d = math.hypot(dx, dy)
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if 0.05 < d < SEPARATION_DIST:
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push = (SEPARATION_DIST - d) / d
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fx -= (dx / d) * push * 2.5
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fy -= (dy / d) * push * 2.5
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# Walls
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if x < X_MIN + WALL_MARGIN: fx += ((X_MIN + WALL_MARGIN - x) / WALL_MARGIN) * 6.0
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if x > X_MAX - WALL_MARGIN: fx -= ((x - (X_MAX - WALL_MARGIN)) / WALL_MARGIN) * 6.0
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if y < Y_MIN + WALL_MARGIN: fy += ((Y_MIN + WALL_MARGIN - y) / WALL_MARGIN) * 6.0
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if y > Y_MAX - WALL_MARGIN: fy -= ((y - (Y_MAX - WALL_MARGIN)) / WALL_MARGIN) * 6.0
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# Wander — suppressed while fleeing so drift cannot deflect the flee heading
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if not fleeing:
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if random.random() < 0.02:
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wander_angle += random.uniform(-0.6, 0.6)
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fx += math.cos(wander_angle) * 0.5
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fy += math.sin(wander_angle) * 0.5
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# Hard-stop clamp: within 0.5 m of a wall, zero any force component that
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# would push further into it. Prevents the flee force from pinning a sheep
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# against the boundary when the dog approaches from outside.
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HS = 0.5
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if x < X_MIN + HS and fx < 0: fx = 0.0
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if x > X_MAX - HS and fx > 0: fx = 0.0
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if y < Y_MIN + HS and fy < 0: fy = 0.0
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if y > Y_MAX - HS and fy > 0: fy = 0.0
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heading = math.atan2(fy, fx)
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mag = math.hypot(fx, fy)
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speed = max(WANDER_SPEED, min(FLEE_SPEED, mag * 3.0))
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drive(heading, speed)
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if step % 3 == 0:
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emitter.send(f"sheep:{name}:{x:.4f}:{y:.4f}")
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