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Find intersection points of rays and occupied map cells



[intersectionPts,isOccupied] = rayIntersection(map3D,sensorPose,directions,maxrange) returns intersection points of rays in the specified map, map3D. Rays emanate from the specified sensorPose at the given orientations, directions. Intersection points are returned in the world coordinate frame. Use isOccupied to determine if the intersection point is at the sensor max range or if it intersects an obstacle.

[intersectionPts,isOccupied] = rayIntersection(map3D,sensorPose,directions,maxrange,ignoreUnknown)additionally accepts optional arguments for the sensors max range and whether to ignore unknown values. By default, the rays extend to the map boundary and unknown values are ignored.


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Import a 3-D occupancy map.

map3D = importOccupancyMap3D("citymap.ot")
map3D = 
  occupancyMap3D with properties:

    ProbabilitySaturation: [1.0000e-03 0.9990]
               Resolution: 1
        OccupiedThreshold: 0.6500
            FreeThreshold: 0.2000

Inflate the occupied areas by a radius of 1 m. Display the map.


Find the intersection points of rays and occupied map cells.

numRays = 10;
angles = linspace(-pi/2,pi/2,numRays);
directions = [cos(angles); sin(angles); zeros(1,numRays)]';
sensorPose = [55 40 1 1 0 0 0];
maxrange = 15;
[intersectionPts,isOccupied] = rayIntersection(map3D,sensorPose,directions,maxrange)
intersectionPts = 10×3

   55.0000   32.0000    1.0000
   57.9118   32.0000    1.0000
   61.7128   32.0000    1.0000
   67.9904   32.5000    1.0000
   69.0000   37.5314    1.0000
   69.0000   42.4686    1.0000
   67.9904   47.5000    1.0000
   64.6418   51.4907    1.0000
   58.2757   49.0000    1.0000
   55.0000   49.0000    1.0000

isOccupied = 10×1


Plot the intersection points and rays from the pose.

hold on
               'FrameSize',5,'MeshFilePath','groundvehicle.stl') % Vehicle sensor pose
for i = 1:numRays
          [sensorPose(3),intersectionPts(i,3)],'-b') % Plot rays
    if isOccupied(i) == 1
        plot3(intersectionPts(i,1),intersectionPts(i,2),intersectionPts(i,3),'*r') % Intersection points

Figure contains an axes object. The axes object with title Occupancy Map contains 22 objects of type patch, line.

Input Arguments

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3-D occupancy map, specified as a occupancyMap3D object.

Position and orientation of sensor, specified as an [x y z qw qx qy qz] vector. The vehicle pose is an xyz-position vector with a quaternion orientation vector specified as [qw qx qy qz].

Orientation of rays emanating from the sensor relative to the sensor coordinate frame, specified as an n-by-3 [dx dy dz] matrix or n-by-2 [az el] matrix.

  • [dx dy dz] is a directional vector in xyz-coordinates.

  • [az el] is a vector with azimuth angle, az, measured from the positive x direction to the positive y direction, and elevation angle from the xy-plane to the positive z-direction in sensor coordinate frame.

Maximum range of laser range sensor, specified as a scalar in meters. Range values greater than or equal to maxrange are considered free along the whole length of the ray, up to maxrange.

Interpret unknown values in the map as free or occupied specified as 1 or 0. Set this value to 0 to assume unknown values are occupied.

Output Arguments

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Intersection points, returned as n-by-3 matrix of [x y z] points in the world frame, where n is the length of directions.

Occupancy status of ray end points, returned as a vector of zeroes and ones. Use isOccupied to determine if the intersection point is at the sensor max range or if it intersects an obstacle.

Version History

Introduced in R2020a