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 or nonrigid transform.

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

Affine Transformations of 3-D Point Cloud

This example shows affine transformation of a 3-D point cloud. The specified forward transform can be a rigid or nonrigid transform. The transformations shown includes rotation (rigid transform) and shearing (nonrigid transform) of the input point cloud.

Read a point cloud into the workspace.

ptCloud = pcread('teapot.ply');

Rotation of 3-D Point Cloud

Create an affine transform object that defines a 45 degree rotation along the z-axis.

A = [cos(pi/4) sin(pi/4) 0 0; ...
     -sin(pi/4) cos(pi/4) 0 0; ...
     0 0 1 0; ...
     0 0 0 1];
tform = affine3d(A);

Transform the point cloud.

ptCloudOut1 = pctransform(ptCloud,tform);

Shearing of 3-D point cloud

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

A = [1 0 0 0; ...
     0.75 1 0 0; ...
     0.75 0 1 0; ...
     0 0 0 1];
tform = affine3d(A);

Transform the point cloud.

ptCloudOut2 = pctransform(ptCloud,tform);

Display the Original and Affine Transformed 3-D Point Clouds

Plot the original 3-D point cloud.

figure1 = figure('WindowState','maximized');
axes1 = axes('Parent',figure1,'Position',[0.28 0.54 0.46 0.41]);
pcshow(ptCloud,'Parent',axes1); 
xlabel('X');
ylabel('Y');
zlabel('Z');
title('3-D Point Cloud','FontSize',14)

Plot the rotation and shear affine transformed 3-D point clouds.

axes2 = axes('Parent',figure1,'Position',[0.15 0.02 0.35 0.42]);
pcshow(ptCloudOut1,'Parent',axes2);
xlabel('X');
ylabel('Y');
zlabel('Z');
title({'Rotation of 3-D Point Cloud'},'FontSize',14)

axes3 = axes('Parent',figure1,'Position',[0.5 0.02 0.35 0.42]);
pcshow(ptCloudOut2,'Parent',axes3);
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.

figure1 = figure('WindowState','maximized');
axes1 = axes('Parent',figure1,'Position',[0.03 0.4 0.35 0.42]);
pcshow(ptCloud,'Parent',axes1)
xlabel('X');
ylabel('Y');
zlabel('Z');
title('Original 3-D Point Cloud','FontSize',14)

axes2 = axes('Parent',figure1,'Position',[0.4 0.4 0.38 0.42]);
pcshow(ptCloudOut,'Parent',axes2)
xlabel('X');
ylabel('Y');
zlabel('Z');
title('Transformed 3-D Point Cloud Using Displacement Field','FontSize',14)

Input Arguments

ptCloudIn — Point cloud

pointCloud object

Point cloud, specified as a pointCloud object.

tform — 3-D affine geometric transformation

affine3d object

3-D affine geometric transformation, specified as an affine3d object. See Define Transformation Matrix (Image Processing Toolbox) for details on how to set up the 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™.

Usage notes and limitations:

• Supports code generation (requires MATLAB^® Coder™) only in generic MATLAB Host Computer target platform.

• Generates code that uses a precompiled, platform-specific shared library.