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Extracting xyzpoints from Point Cloud

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I want to extract xyz points data from Point Cloud model.
pointCloud with properties:
Location: [14816040×3 single]
Count: 14816040
XLimits: [-122.5566 183.8412]
YLimits: [-214.3051 106.7991]
ZLimits: [-4.3266 6.3947]
Color: [14816040×3 uint8]
Normal: [14816040×3 single]
Intensity: []
I am using two provided ways but not getting any results.
1st Code
ptCloud = pcread('M.ply');
xyzPoints = ptCloud.Location;
x = xyzPoints(:,:,1);
y = xyzPoints(:,:,2);
z = xyzPoints(:,:,3);
points3D = [x(:)'; y(:)', z(:)'];
Index in position 3 exceeds array bounds. Index must not exceed 1.
Error in xyzextract (line 8)
y = xyzPoints(:,:,2);
2nd function is
pts = rosReadXYZ(ptCloud)
Error using rosReadXYZ
Expected input to be one of these types:
Instead its type was pointCloud.
Error in rosReadXYZ (line 46)
Error in xyzextract (line 13)
pts = rosReadXYZ(ptCloud,"PreserveStructureOnRead",true);
Kindly advise, I just want to extract xyz points from Point Cloud.

Accepted Answer

Sean de Wolski
Sean de Wolski on 23 Apr 2022
The location is the xyz points and it's 2d, not 3d like how you're indexing it.
points3d = ptCloud.Location.';
Would give you what you're after.
Sean de Wolski
Sean de Wolski on 25 Apr 2022
You'd call it with
pointcloud2image(ptCloud.Location(:,1), ptCloud.Location(:,2), ptCloud.Location(:,3), nrows, ncols)
Additionally, you could probably just call scatteredInterpolant directly.
Abdul Hannan Qureshi
Abdul Hannan Qureshi on 25 Apr 2022
@Sean de Wolski Thank you for clarrification. I will try that, I have clear preview now. Thanks again.

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More Answers (2)

Walter Roberson
Walter Roberson on 23 Apr 2022
Edited: Walter Roberson on 24 Apr 2022
Location: [14816040×3 single]
That tells you that the position information is 14816040 x 3 . It is not a 3D array.
Pointclouds store scattered information, not grids of information.
In some cases it may make sense to reshape() the scattered coordinates into a grid after it is extracted.
The information you get from the Location property is already the points3D array that you are trying to construct.
(Opps, Sean is right, you would need to take the transpose like he shows.)

Naveed on 20 Apr 2024
Hi there!
How to access the features e.g (xyz, rgb values) in point cloud?
please help me out with this!
Walter Roberson
Walter Roberson on 20 Apr 2024
Are you getting an error message? If so, what is the error?
Note that rgb can come out empty if there is no RGB information stored in the point cloud.
Naveed on 20 Apr 2024
clear all;
close all;
ptcloud = pcread("C:\Users\PMLS\Desktop\FYP\tape-ply.ply");
points = ptcloud.Location;
colors = ptcloud.Color;
disp(['Number of points: ', num2str(ptcloud.Count)]);
player = pcplayer(ptcloud.XLimits, ptcloud.YLimits, ptcloud.ZLimits);
view(player, ptcloud);
the output is: Number of points: 84062 but having no rgb values.

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