raycast

Compute cell indices along a ray

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Syntax

[endpoints,midpoints] = raycast(map,pose,range,angle)
[endpoints,midpoints] = raycast(map,p1,p2)

Description

The raycast function computes and returns the map cell indices traversed by a ray or line segment between specified points or from a pose at a given angle and range.

[endpoints,midpoints] = raycast(map,pose,range,angle) returns cell indices of the specified map for all cells traversed by a ray originating from the specified pose at the specified angle and range values. endpoints contains all indices touched by the end of the ray, with all other points included in midpoints.

example

[endpoints,midpoints] = raycast(map,p1,p2) returns the cell indices of the line segment between the two specified points.

Examples

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This example uses:

Open Live Script

Use the raycast function to generate cell indices for all cells traversed by a ray.

Create an empty map. A low-resolution map is used to illustrate the affected grid locations.

map = binaryOccupancyMap(10,10,1);
show(map)

Figure contains an axes object. The axes object with title Binary Occupancy Grid, xlabel X [meters], ylabel Y [meters] contains an object of type image.

Get the grid indices of the midpoints and end points of a ray from [2 3] to [8.5 8]. Set occupancy values for these grid indices. Midpoints are treated as open space. Update endpoints with an occupied observation.

p1 = [2 3];
p2 = [8.5 8];
[endPts,midPts] = raycast(map,p1,p2);
setOccupancy(map,midPts,zeros(length(midPts),1),'grid');
setOccupancy(map,endPts,ones(length(endPts),1),'grid');

Plot the original ray over the map. Each grid cell touched by the line is updated. The starting point overlaps multiple cells, and the line touches the edge of certain cells, but all the cells are still updated.

show(map)
hold on
plot([p1(1) p2(1)],[p1(2) p2(2)],"-b","LineWidth",2)
plot(p2(1),p2(2),"or")
grid on

Figure contains an axes object. The axes object with title Binary Occupancy Grid, xlabel X [meters], ylabel Y [meters] contains 3 objects of type image, line. One or more of the lines displays its values using only markers

Input Arguments

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Map representation, specified as a binaryOccupancyMap object. This object represents the environment of the robot. The object contains a matrix grid with binary values indicating obstacles as true (1) and free locations as false (0).

Position and orientation of sensor, specified as an [x y theta] vector. The sensor pose is an x and y position with angular orientation theta (in radians) measured from the x-axis.

Range of ray, specified as a scalar in meters.

Angle of ray, specified as a scalar in radians. The angle value is for the corresponding range.

Starting point of ray, specified as an [x y] two-element vector. Points are defined with respect to the world-frame.

Endpoint of ray, specified as an [x y] two-element vector. Points are defined with respect to the world-frame.

Output Arguments

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Endpoint indices, returned as an n-by-2 matrix of [i j] pairs, where n is the number of grid indices. The endpoints are where the range value hits at the specified angle. Multiple indices are returned when the endpoint lies on the boundary of multiple cells.

Midpoint indices, returned as an n-by-2 matrix of [i j] pairs, where n is the number of grid indices. This argument includes all grid indices the ray intersects, excluding the endpoint.

Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2019b

See Also

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