show

Visualize path metrics in map environment

Syntax

show(pathMetricsObj)

show(pathMetricsObj,Name,Value)

axHandle = show(pathMetricsObj)

Description

show(pathMetricsObj) plots the path in the map environment with the minimum clearance.

show(pathMetricsObj,Name,Value) specifies additional options using one or more name-value pair arguments.

axHandle = show(pathMetricsObj) outputs the axes handle of the figure used to plot the path.

Examples

Compute Path Metrics

Compute smoothness, clearance, and validity of a planned path based on a set of poses and the associated map environment.

Load and Assign Map to State Validator

Create an occupancy map from an example map and set the map resolution.

load exampleMaps.mat; % simpleMap
mapResolution = 1; % cells/meter
map = occupancyMap(simpleMap,mapResolution);

Create a Dubins state space.

statespace = stateSpaceDubins;

Create a state validator based on occupancy map to store the parameters and states in the Dubins state space.

statevalidator = validatorOccupancyMap(statespace);

Assign the map to the validator.

statevalidator.Map = map;

Set the validation distance for the validator.

statevalidator.ValidationDistance = 0.01;

Update the state space bounds to be the same as the map limits.

statespace.StateBounds = [map.XWorldLimits;map.YWorldLimits;[-pi pi]];

Plan Path

Create an RRT* path planner and allow further optimization.

planner = plannerRRTStar(statespace,statevalidator);
planner.ContinueAfterGoalReached = true;

Reduce the maximum number of iterations and increase the maximum connection distance.

planner.MaxIterations = 2500;
planner.MaxConnectionDistance = 0.3;

Define start and goal states for the path planner as [x, y, theta] vectors. x and y are the Cartesian coordinates, and theta is the orientation angle.

start = [2.5, 2.5, 0]; % [meters, meters, radians]
goal = [22.5, 8.75, 0];

Plan a path from the start state to the goal state. The plan function returns a navPath object.

rng(100,'twister') % repeatable result
[path,solutionInfo] = plan(planner,start,goal);

Compute and Visualize Path Metrics

Create a path metrics object.

pathMetricsObj = pathmetrics(path,statevalidator);

Check path validity. The result is 1 (true) if the planned path is obstacle free. 0 (false) indicates an invalid path.

isPathValid(pathMetricsObj)

ans = logical
   1

Calculate the minimum clearance of the path.

clearance(pathMetricsObj)

ans = 1

Evaluate the smoothness of the path. Values close to 0 indicate a smoother path. Straight-line paths return a value of 0.

smoothness(pathMetricsObj)

ans = 1.7453

Visualize the minimum clearance of the path.

show(pathMetricsObj)
legend('Planned Path','Minimum Clearance')

Vehicle Path Planning and Metrics Computation in a 2-D Costmap Environment

Plan a vehicle path through a parking lot using the RRT* algorithm. Compute and visualize the smoothness, clearance, and validity of the planned path.

Load and Assign Map to State Validator

Load a costmap of a parking lot. Plot the costmap to see the parking lot and the inflated areas that the vehicle should avoid.

load parkingLotCostmap.mat;
costmap = parkingLotCostmap;
plot(costmap)
xlabel('X (meters)')
ylabel('Y (meters)')

Create a stateSpaceDubins object and increase the minimum turing radius to 4 meters.

statespace = stateSpaceDubins;
statespace.MinTurningRadius = 4; % meters

Create a validatorVehicleCostmap object using the created state space.

statevalidator = validatorVehicleCostmap(statespace);

Assign the parking lot costmap to the state validator object.

statevalidator.Map = costmap;

Plan Path

Define start and goal poses for the vehicle as [x, y, Θ] vectors. World units for the (x,y) locations are in meters. World units for the orientation angles Θ are in degrees.

startPose = [5, 5, 90]; % [meters, meters, degrees]
goalPose = [40, 38, 180]; % [meters, meters, degrees]

Use a pathPlannerRRT (Automated Driving Toolbox) object and the plan (Automated Driving Toolbox) function to plan the vehicle path from the start pose to the goal pose.

planner = pathPlannerRRT(costmap);
refPath = plan(planner,startPose,goalPose);

Interpolate along the path at every one meter. Convert the orientation angles from degrees to radians.

poses = zeros(size(refPath.PathSegments,2)+1,3);
poses(1,:) = refPath.StartPose;
for i = 1:size(refPath.PathSegments,2) 
    poses(i+1,:) = refPath.PathSegments(i).GoalPose; 
end
poses(:,3) = deg2rad(poses(:,3));

Create a navPath object using the Dubins state space object and the states specified by poses.

path = navPath(statespace,poses);

Compute and Visualize Path Metrics

Create a pathmetrics object.

pathMetricsObj = pathmetrics(path,statevalidator);

Check path validity. The result is 1 (true) if the planned path is obstacle free. 0 (false) indicates an invalid path.

isPathValid(pathMetricsObj)

ans = logical
   1

Compute and visualize the minimum clearance of the path.

clearance(pathMetricsObj)

ans = 0.5000

show(pathMetricsObj)
legend('Inflated Areas','Planned Path','Minimum Clearance')
xlabel('X (meters)')
ylabel('Y (meters)')

Compute and visualize the smoothness of the path. Values close to 0 indicate a smoother path. Straight-line paths return a value of 0.

smoothness(pathMetricsObj)

ans = 0.0842

show(pathMetricsObj,'Metrics',{'Smoothness'})
legend('Inflated Areas','Path Smoothness')
xlabel('X (meters)')
ylabel('Y (meters)')

Visualize the clearance for each state of the path.

show(pathMetricsObj,'Metrics',{'StatesClearance'})
legend('Inflated Areas','Planned Path','Clearance of Path States')
xlabel('X (meters)')
ylabel('Y (meters)')

Input Arguments

pathMetricsObj — Information for path metrics

pathmetrics object

Information for path metrics, specified as a pathmetrics object.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'Parent',axHandle

'Parent' — Axes used to plot path

Axes object | UIAxes object

Axes used to plot path, specified as the comma-separated pair consisting of 'Parent' and either an axes or uiaxes object. If you do not specify Parent, a new figure is created.

Example: show(pathMetricsObj,'Parent',axHandle)

'Metrics' — Display metrics option

cell array of strings

Display metrics option, specified as the comma-separated pair consisting of 'Metrics' and a cell array with any combination of these values:

• 'MinClearance' — Display minimum clearance of path.

• 'StatesClearance' — Display clearance of path states.

• 'Smoothness' — Display path smoothness.

Example: show(pathMetricsObj,'Metrics',{'Smoothness','StatesClearance'})

Data Types: cell

Output Arguments

axHandle — Axes used to plot path

Axes object | UIAxes object

Axes used to plot path, returned as either an axes or uiaxes object.