pctransform

Transform 3-D point cloud

Syntax

ptCloudOut = pctransform(ptCloudIn,tform)

ptCloudOut = pctransform(ptCloudIn,D)

Description

ptCloudOut = pctransform(ptCloudIn,tform) applies the specified 3-D affine transform, tform to the point cloud, ptCloudIn. The transformation can be a rigid, similarity, or affine transformation.

ptCloudOut = pctransform(ptCloudIn,D) applies the displacement field D to the point cloud. Point cloud transformation using a displacement field define translations with respect to each point in the point cloud.

Examples

Rotate 3-D Point Cloud Using Rigid Transformation

Read a point cloud.

ptCloud = pcread('teapot.ply');

Plot the point cloud.

figure
pcshow(ptCloud)
xlabel('X')
ylabel('Y')
zlabel('Z')

Create a transformation object with a 45 degree rotation along the z-axis.

rotationAngles = [0 0 45];
translation = [0 0 0];
tform = rigidtform3d(rotationAngles,translation);

Transform the point cloud.

ptCloudOut = pctransform(ptCloud,tform);

Plot the transformed point cloud.

figure
pcshow(ptCloudOut)
xlabel('X')
ylabel('Y')
zlabel('Z')

Rigid and Nonrigid Transformations of 3-D Point Cloud

This example applies a rigid transformation (rotation) and a nonrigid transformation (shear) to a 3-D point cloud.

Read a point cloud into the workspace.

ptCloud = pcread('teapot.ply');

Plot the original 3-D point cloud.

figure1 = figure;
axes1 = axes(Parent=figure1);
pcshow(ptCloud,Parent=axes1,AxesVisibility='on'); 
xlabel('X');
ylabel('Y');
zlabel('Z');
title('3-D Point Cloud',FontSize=14)

Rotation of 3-D Point Cloud

Create a rigid transformation object that defines a 45 degree rotation along the z-axis.

rotationAngles = [0 0 45];
translation = [0 0 0];
tform = rigidtform3d(rotationAngles,translation);

Transform the point cloud.

ptCloudOut1 = pctransform(ptCloud,tform);

Plot the rotated point cloud.

figure2 = figure;
axes2 = axes(Parent=figure2);
pcshow(ptCloudOut1,Parent=axes2,AxesVisibility='on');
xlabel('X');
ylabel('Y');
zlabel('Z');
title({'Rotation of 3-D Point Cloud'},FontSize=14)

Shearing of 3-D Point Cloud

Create an affine transformation object that defines shearing along the x-axis.

A = [1 0.75 0.75 0; ...
     0   1    0  0; ...
     0   0    1  0; ...
     0   0    0  1];
tform = affinetform3d(A);

Transform the point cloud.

ptCloudOut2 = pctransform(ptCloud,tform);

Plot the transformed point cloud.

figure3 = figure;
axes3 = axes(Parent=figure3);
pcshow(ptCloudOut2,Parent=axes3,AxesVisibility='on');
xlabel('X');
ylabel('Y');
zlabel('Z');
title({'Shearing of 3-D Point Cloud'},FontSize=14)

Point Cloud Transformation Using Displacement Field

Read a point cloud into the workspace.

ptCloud = pcread('teapot.ply');

Create a displacement field D of same size as the point cloud.

D = zeros(size(ptCloud.Location));

Set the displacement field value along x-axis for the first half of the points to 7.

pthalf = ptCloud.Count/2;
D(1:pthalf,1) = 7;

Extract the indices of points within a region-of-interest (ROI) using the pointCloud method findNeighborsInRadius. Set the displacement field value along the x-, y-, and z-axis for points within the ROI to 4, 4, and -2, respectively.

indices = findNeighborsInRadius(ptCloud,[0 0 3.1],1.5);
D(indices,1:2) = 4;
D(indices,3) = -2;

Transform the point cloud using the displacement field.

ptCloudOut = pctransform(ptCloud,D);

Display the original and transformed point cloud.

figure
pcshow(ptCloud)
xlabel('X');
ylabel('Y');
zlabel('Z');
title('Original 3-D Point Cloud')

figure
pcshow(ptCloudOut)
xlabel('X');
ylabel('Y');
zlabel('Z');
title('Transformed 3-D Point Cloud Using Displacement Field')

Input Arguments

ptCloudIn — Point cloud

pointCloud object

Point cloud, specified as a pointCloud object.

tform — 3-D geometric transformation

rigidtform3d object | simtform3d object | affinetform3d object

3-D geometric transformation, specified as a rigidtform3d, simtform3d, or affinetform3d object. See Specify Transformation Matrix for details on how to set up an affine 3-D tform input.

D — Displacement field

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

Displacement field, specified as either M-by-3 or an M-by-N-by-3 array. The displacement field is a set of displacement vectors that specify the magnitude and direction of translation for each point in the point cloud. The size of the displacement field must be the same as the size of the Location property of the pointCloud object.

Data Types: single | double

Output Arguments

ptCloudOut — Transformed point cloud

pointCloud object

Transformed point cloud, returned as a pointCloud object. The transformation applies to the coordinates of points and their normal vectors.

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™.

Version History

Introduced in R2015a

R2022b: Supports new geometric transformation objects

Starting in R2022b, most Computer Vision Toolbox™ functions create and perform geometric transformations using the premultiply convention. Accordingly, you can now specify tform as a rigidtform3d, simtform3d, or affinetform3d object, which use the premultiply convention.

Although you can still specify tform as a rigid3d object or an affine3d object, these objects are not recommended because they use the postmultiply convention. You can streamline your geometric transformation workflows by switching to the new premultiply geometric transformation objects. For more information, see Migrate Geometric Transformations to Premultiply Convention.