cubicLaneBoundary

Cubic lane boundary model

Description

The cubicLaneBoundary object contains information about a cubic lane boundary model.

Creation

To generate cubic lane boundary models that fit a set of boundary points and an approximate width, use the findCubicLaneBoundaries function. If you already know your cubic parameters, create lane boundary models by using the cubicLaneBoundary function (described here).

Description

example

boundaries = cubicLaneBoundary(cubicParameters) creates an array of cubic lane boundary models from an array of [A B C D] parameters for the cubic equation y = Ax3 + Bx2 + Cx + D. Points within the lane boundary models are in world coordinates.

Input Arguments

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Parameters for cubic models of the form y = Ax3 + Bx2 + Cx + D, specified as an [A B C D] real-valued vector or as a matrix of [A B C D] values. Each row of cubicParameters describes a separate cubic lane boundary model.

Properties

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Coefficients for a cubic model of the form y = Ax3 + Bx2 + Cx + D, specified as an [A B C D] real-valued vector.

Type of boundary, specified as a LaneBoundaryType of supported lane boundaries. The supported lane boundary types are:

  • Unmarked

  • Solid

  • Dashed

  • BottsDots

  • DoubleSolid

Specify a lane boundary type as LaneBoundaryType.BoundaryType. For example:

LaneBoundaryType.BottsDots

Strength of the boundary model, specified as a real scalar. Strength is the ratio of the number of unique x-axis locations on the boundary to the length of the boundary specified by the XExtent property. A solid line without any breaks has a higher strength than a dotted line that has breaks along the full length of the boundary.

Length of the boundary along the x-axis, specified as a [minX maxX] real-valued vector that describes the minimum and maximum x-axis locations.

Object Functions

computeBoundaryModelObtain y-coordinates of lane boundaries given x-coordinates

Examples

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Create left-lane and right-lane cubic boundary models.

llane = cubicLaneBoundary([-0.0001 0.0 0.003  1.6]);
rlane = cubicLaneBoundary([-0.0001 0.0 0.003 -1.8]);

Create a bird's-eye plot and lane boundary plotter. Plot the lane boundaries.

bep = birdsEyePlot('XLimits',[0 30],'YLimits',[-10 10]);
lbPlotter = laneBoundaryPlotter(bep,'DisplayName','Lane boundaries');

plotLaneBoundary(lbPlotter, [llane rlane]);

Find lanes in an image by using cubic lane boundary models. Overlay the identified lanes on the original image and on a bird's-eye-view transformation of the image.

Load an image of a road with lanes. The image was obtained from a camera sensor mounted on the front of a vehicle.

I = imread('road.png');

Transform the image into a bird's-eye-view image by using a preconfigured sensor object. This object models the sensor that captured the original image.

bevSensor = load('birdsEyeConfig');
birdsEyeImage = transformImage(bevSensor.birdsEyeConfig,I);
imshow(birdsEyeImage)

Set the approximate lane marker width in world units (meters).

approxBoundaryWidth = 0.25;

Detect lane features and display them as a black-and-white image.

birdsEyeBW = segmentLaneMarkerRidge(rgb2gray(birdsEyeImage), ...
    bevSensor.birdsEyeConfig,approxBoundaryWidth);
imshow(birdsEyeBW)

Obtain lane candidate points in world coordinates.

[imageX,imageY]  = find(birdsEyeBW);
xyBoundaryPoints = imageToVehicle(bevSensor.birdsEyeConfig,[imageY,imageX]);

Find lane boundaries in the image by using the findCubicLaneBoundaries function. By default, the function returns a maximum of two lane boundaries. The boundaries are stored in an array of cubicLaneBoundary objects.

boundaries = findCubicLaneBoundaries(xyBoundaryPoints,approxBoundaryWidth);

Use insertLaneBoundary to overlay the lanes on the original image. The XPoints vector represents the lane points, in meters, that are within range of the ego vehicle's sensor. Specify the lanes in different colors. By default, lanes are yellow.

XPoints = 3:30;

figure
sensor = bevSensor.birdsEyeConfig.Sensor;
lanesI = insertLaneBoundary(I,boundaries(1),sensor,XPoints);
lanesI = insertLaneBoundary(lanesI,boundaries(2),sensor,XPoints,'Color','green');
imshow(lanesI)

View the lanes in the bird's-eye-view image.

figure
BEconfig = bevSensor.birdsEyeConfig;
lanesBEI = insertLaneBoundary(birdsEyeImage,boundaries(1),BEconfig,XPoints);
lanesBEI = insertLaneBoundary(lanesBEI,boundaries(2),BEconfig,XPoints,'Color','green');
imshow(lanesBEI)

Introduced in R2018a