findPointsInModel

Find points in or on surface of geometric model

Since R2024a

Syntax

indices = findPointsInModel(model,ptCloud)

Description

indices = findPointsInModel(model,ptCloud) finds the points in the point cloud ptCloud that are located inside or on the surface of the geometric shape specified by model, and returns their linear indices.

Examples

Find Points of Cylinder Model in Point Cloud

Load a MAT file containing point cloud data into the workspace.

load("object3d.mat")

Visualize the point cloud.

figure
pcshow(ptCloud)

Define a region of interest (ROI) in the point cloud in which to detect a cylinder model.

roi = [0.4 0.7; -0.1 0.2; 0 0.4];
sampleIndices = findPointsInROI(ptCloud,roi);

Set a maximum point-to-cylinder distance of 5 mm for cylinder fitting and the orientation constraint.

maxDistance = 0.005;
referenceVector = [0 0 1];

Detect a cylinder in the point cloud.

 model = pcfitcylinder(ptCloud,maxDistance,referenceVector, ...
        SampleIndices=sampleIndices);

Create a synthetic point cloud that is evenly distributed and covers the region of interest.

gridStep = 0.005;
[x,y,z] = meshgrid(roi(1,1):gridStep:roi(1,2),roi(2,1):gridStep:roi(2,2), ...
roi(3,1):gridStep:roi(3,2));
syntheticPtCloud = pointCloud([x(:) y(:) z(:)],Color=[0.7 0.7 0.8]);

Find the points in the synthetic point cloud that are in the cylinder.

idx = findPointsInModel(model,syntheticPtCloud);
cylinderPtCloud = select(syntheticPtCloud,idx);

Visualize the resulting point cloud, with the synthetic points in the cylinder modeling the object on the table.

figure
pcshow(cylinderPtCloud)
hold on
pcshow(ptCloud)

Find Points of Sphere Model in Point Cloud

Load a MAT file containing a point cloud into the workspace.

load("object3d.mat")

Visualize the point cloud.

figure
pcshow(ptCloud)

Define a region of interest (ROI) in the point cloud in which to detect a sphere model.

roi = [0.2 0.55; 0.2 0.5; 0 0.5];
sampleIndices = findPointsInROI(ptCloud,roi);

Set a maximum point-to-sphere distance of 5mm for sphere fitting.

maxDistance = 0.005;

Detect the sphere in the point cloud.

[model,inlierIdx] = pcfitsphere(ptCloud,maxDistance,SampleIndices=sampleIndices);

Find one of the colors in the detected sphere, to use for the synthetic point cloud.

inlierPtCloud = select(ptCloud,inlierIdx);
color = median(inlierPtCloud.Color);

Create a synthetic point cloud that is evenly distributed and covers the region of interest.

gridStep = 0.005;
[x,y,z] = meshgrid(roi(1,1):gridStep:roi(1,2),roi(2,1):gridStep:roi(2,2), ...
roi(3,1):gridStep:roi(3,2));
syntheticPtCloud = pointCloud([x(:) y(:) z(:)],Color=color);

Find the points in the synthetic point cloud that are in the sphere.

idx = findPointsInModel(model,syntheticPtCloud);
spherePtCloud = select(syntheticPtCloud,idx);

Visualize the resulting point cloud, with the synthetic points in the sphere modeling the object on the table.

figure
pcshow(spherePtCloud)
hold on
pcshow(ptCloud)

Input Arguments

model — Parametric model

cylinderModel object | sphereModel object

Parametric model, specified as a cylinderModel or sphereModel object.

ptCloud — Point cloud

pointCloud object

Point cloud in the sensor coordinate system, specified as a pointCloud object.

Output Arguments

indices — Linear indices of point cloud points

column vector

Linear indices of the point cloud points that are located inside or on the surface of the model, returned as a column vector.

Version History

Introduced in R2024a