3_1_obstacle.md

3.1 Obstacle

This section explains the obstacle models used by the sensor simulations. The repository provides two modules:

• obstacle.py: Represents one obstacle (static or dynamic).
• obstacle_list.py: Manages multiple obstacles.

3.1.1 Rectangle Obstacle

The Obstacle class stores its own state and geometric shape. The constructor takes a State class instance and shape/motion parameters.

class Obstacle:
    def __init__(self, state, accel_mps2=0.0, yaw_rate_rps=0.0,
                 length_m=2.0, width_m=2.0):
        self.state = state
        self.accel_mps2 = accel_mps2
        self.yaw_rate_rps = yaw_rate_rps
        self.length_m = length_m
        self.width_m = width_m

Notes:

• accel_mps2 and yaw_rate_rps control obstacle motion.
• When both are 0.0, the obstacle behaves as a static object.
• width_m is treated as half-width in the class contour definition.

The update function advances obstacle motion using the state model:

def update(self, time_s):
    self.state.update(self.accel_mps2, self.yaw_rate_rps, time_s)

The draw function transforms the rectangle contour from obstacle coordinates to global coordinates and plots it:

def draw(self, axes, elems):
    x_m = self.state.get_x_m()
    y_m = self.state.get_y_m()
    yaw_rad = self.state.get_yaw_rad()

    transformed_array = self.array.homogeneous_transformation(x_m, y_m, yaw_rad)
    obstacle_plot, = axes.plot(transformed_array.get_x_data(),
                               transformed_array.get_y_data(),
                               lw=1.0, color='k', ls='-')
    elems.append(obstacle_plot)

The vertex_xy() method returns transformed corner coordinates for downstream modules such as LiDAR point-cloud generation.

3.1.2 Obstacles List

ObstacleList is a small container class for multiple obstacles:

class ObstacleList:
    def __init__(self):
        self.list = []

    def add_obstacle(self, obstacle):
        self.list.append(obstacle)

It also provides batch update() and draw() calls, plus get_list() for other modules (for example, LiDAR).

3.1.3 Visualization

A sample script for obstacle visualization is provided:

• visualize_obstacle.py

This script creates one static obstacle and two dynamic obstacles, then draws them in the simulation world together with a vehicle model.

The output example is: