pointCloud

Object for storing 3-D point cloud

Description

The pointCloud object creates point cloud data from a set of points in 3-D coordinate system The points generally represent the x,y, and z geometric coordinates of a samples surface or an environment. Each point can also be represented with additional information, such as RGB color. The point cloud data is stored as an object with the properties listed in Properties. Use Object Functions to retrieve, select, and remove desired points from the point cloud data.

Creation

Syntax

ptCloud = pointCloud(xyzPoints)

ptCloud = pointCloud(xyzPoints,Name,Value)

Description

ptCloud = pointCloud(xyzPoints) returns a point cloud object with coordinates specified by xyzPoints.

ptCloud = pointCloud(xyzPoints,Name,Value) creates a pointCloud object with properties specified as one or more Name,Value pair arguments. For example, pointCloud(xyzPoints,'Color',[0 0 0]) sets the Color property of the point xyzPoints as [0 0 0]. Enclose each property name in quotes. Any unspecified properties have default values.

Input Arguments

xyzPoints — 3-D coordinate points

M-by-3 list of points | M-by-N-by-3 array for organized point cloud

3-D coordinate points, specified as an M-by-3 list of points or an M-by-N-by-3 array for an organized point cloud. The 3-D coordinate points specify the x, y, and z positions of a point in the 3-D coordinate space. The first two dimensions of an organized point cloud correspond to the scanning order from sensors such as RGBD or lidar. This argument sets the Location property.

Data Types: single | double

Output Arguments

ptCloud — Point cloud

pointCloud object

Point cloud, returned as a pointCloud object with the properties listed in Properties.

Properties

Location — Position of the points in 3-D coordinate space

M-by-3 array | M-by-N-by-3 array

This property is read-only.

Position of the points in 3-D coordinate space, specified as an M-by-3 or M-by-N-by-3 array. Each entry specifies the x, y, and z coordinates of a point in the 3-D coordinate space. You cannot set this property as a name-value pair. Use the xyzPoints input argument.

• For unorganized point clouds, Location must be specified as an M-by-3 array, where M is the total number of points in the point cloud.

• For organized point clouds, Location must be specified as an M-by-N-by-3 array. The three channels represent the x, y, and z coordinates of the points. Points obtained from a projective camera, such as Kinect^®or a lidar sensor, are stored as an organized point cloud.

Data Types: single | double

Color — Point cloud color

[ ] (default) | M-by-3 array | M-by-N-by-3 array

Point cloud color, specified as an M-by-3 or M-by-N-by-3 array. Use this property to set the color of points in point cloud. Each entry specifies the RGB color of a point in the point cloud data. Therefore, you can specify the same color for all points or a different color for each point.

• The specified RGB values must lie within the range [0, 1], when you specify the data type for Color as single or double.

• The specified RGB values must lie within the range [0, 255], when you specify the data type for Color as uint8.

Coordinates	Valid assignment of Color
M-by-3 array	M-by-3 array containing RGB values for each point
M-by-N-by-3 array	M-by-N-by-3 array containing RGB values for each point

Data Types: uint8

Normal — Surface normals

[ ] (default) | M-by-3 array | M-by-N-by-3 array

Surface normals, specified as a M-by-3 or M-by-N-by-3 array. Use this property to specify the normal vector with respect to each point in the point cloud. Each entry in the surface normals specifies the x, y, and z component of a normal vector.

Coordinates	Surface Normals
M-by-3 array	M-by-3 array, where each row contains a corresponding normal vector.
M-by-N-by-3 array	M-by-N-by-3 array containing a 1-by-1-by-3 normal vector for each point.

Data Types: single | double

Intensity — Grayscale intensities

[ ] (default) | M-by-1 vector | M-by-N matrix

Grayscale intensities at each point, specified as a M-by-1 vector or M-by-N matrix. The function maps each intensity value to a color value in the current colormap.

Coordinates	Intensity
M-by-3 array	M-by-1 vector, where each row contains a corresponding intensity value.
M-by-N-by-3 array	M-by-N matrix containing intensity value for each point.

Data Types: single | double | uint8

Count — Number of points

positive integer

This property is read-only.

Number of points in the point cloud, stored as a positive integer.

XLimits — Range of x coordinates

1-by-2 vector

This property is read-only.

Range of coordinates along x-axis, stored as a 1-by-2 vector.

YLimits — Range of y coordinates

1-by-2 vector

This property is read-only.

Range of coordinates along y-axis, stored as a 1-by-2 vector.

ZLimits — Range of z coordinates

1-by-2 vector

This property is read-only.

Range of coordinates along z-axis, stored as a 1-by-2 vector.

Object Functions

findNearestNeighbors	Find nearest neighbors of a point in point cloud
findNeighborsInRadius	Find neighbors within a radius of a point in the point cloud
findPointsInROI	Find points within a region of interest in the point cloud
removeInvalidPoints	Remove invalid points from point cloud
select	Select points in point cloud
copy	Copy array of handle objects

Examples

Create a Point Cloud Object and Modify its Properties

Read the 3-D coordinate points into the workspace.

load('xyzPoints');

Create a point cloud object from the input point coordinates.

ptCloud = pointCloud(xyzPoints);

Inspect the properties of the point cloud object.

ptCloud

ptCloud = 
  pointCloud with properties:

     Location: [5184x3 single]
        Count: 5184
      XLimits: [-3 3.4338]
      YLimits: [-2 2]
      ZLimits: [0.0016 3.1437]
        Color: []
       Normal: []
    Intensity: []

Display the point cloud by using pcshow.

pcshow(ptCloud)

Modify Color of Point Cloud Data

Create an RGB color array of size same as the size of the point cloud data. Set the point colors to Red.

cmatrix = ones(size(ptCloud.Location)).*[1 0 0];

Create the point cloud object with the color property set to the RGB color array.

ptCloud = pointCloud(xyzPoints,'Color',cmatrix);
pcshow(ptCloud)

Add Surface Normals to Point Cloud Data

Compute surface normals corresponding to the point cloud data using pcnormals.

normals = pcnormals(ptCloud);

Create point cloud object from input point coordinates. Add the computed surface normals to point cloud object.

ptCloud = pointCloud(xyzPoints,'Normal',normals);

Display the point cloud and plot the surface normals.

pcshow(ptCloud)
x = ptCloud.Location(:,1);
y = ptCloud.Location(:,2);
z = ptCloud.Location(:,3);
u = normals(:,1);
v = normals(:,2);
w = normals(:,3);
hold on
quiver3(x,y,z,u,v,w);
hold off

Tips

The pointCloud object is a handle object. If you want to create a separate copy of a point cloud, you can use the MATLAB^® copy method.

ptCloudB = copy(ptCloudA)

If you want to preserve a single copy of a point cloud, which can be modified by point cloud functions, use the same point cloud variable name for the input and output.

ptCloud = pcFunction(ptCloud)

Extended Capabilities

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

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

• GPU code generation for variable input sizes is not optimized. Consider using constant size inputs for an optimized code generation.

• GPU code generation supports the 'Color', 'Normal', and 'Intensity' name-value pairs.

• GPU code generation supports the findNearestNeighbors, findNeighborsInRadius, findPointsInROI, removeInvalidPoints, and select methods.

• For very large inputs, the memory requirements of the algorithm may exceed the GPU device limits. In such cases, consider reducing the input size to proceed with code generation.