plot

R2026b

Visualize 3-D point cloud and camera trajectory from structure-from-motion (SfM) reconstruction

Since R2026b

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Syntax

plot(sfmObj)
plot(sfmObj,Name=Value)

Description

plot(sfmObj) plots the reconstructed 3-D points and estimated camera trajectory stored in the sfm object sfmObj. Visualize intermediate or final results of reconstruction using the plot function at any stage after calling the triangulateInitialViews object function.

example

plot(sfmObj,Name=Value) specifies visualization options using one or more name-value arguments. For example, plot(sfmObj,CameraSize=0.3) increases the displayed camera size.

Examples

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Open Live Script

Use the sfm object to recover camera poses and a sparse 3-D point cloud from images of an indoor scene.

Create Image Datastore and Define Camera Intrinsics

Create an ImageDatastore from the image sequence. Specify the camera intrinsic parameters.

unzip("sfm_images.zip")
imageFolder = fullfile(pwd,"images");
imds = imageDatastore(imageFolder);
intrinsics = cameraIntrinsics([535.1307 532.1860],[323.3722 239.7986],[480 640]);

Visualize the indoor scene.

imshow(preview(imds))

Create SfM Object and Run Pipeline

Create an sfm object and execute each stage of the incremental SfM pipeline sequentially.

sfmObj = sfm(imds,intrinsics);

Connect image pairs based on visual similarity.

sfmObj = connectImagePairs(sfmObj);

Visualize the similarity matrix for the connected image pairs using the imagesc function.

imagesc(sfmObj.SimilarityMatrix)
title("Similarity Matrix for Connected Image Pairs")

Verify that the view graph was created successfully before proceeding to geometric verification.

if isConnected(sfmObj)
    sfmObj = verifyImagePairs(sfmObj);
end

Visualize the similarity matrix for the refined image pair connections using the imagesc function.

imagesc(sfmObj.SimilarityMatrix)
title("Similarity Matrix after Refining Connected Image Pairs")

Confirm that geometric verification completed successfully before initializing the reconstruction. Specify a minimum median angle of 5 degrees and a maximum triangulation error of 4 pixels. Display the initialization metrics.

if isVerified(sfmObj)
    [sfmObj,info] = triangulateInitialViews(sfmObj,MinMedianAngle=5,MaxTriangulationError=4);
    disp(info)
end
                     ViewId1: 9
                     ViewId2: 10
                RelativePose: [1×1 rigidtform3d]
                     Matches: [380×2 uint32]
    MedianTriangulationAngle: 8.6016
       MeanReprojectionError: 0.2799

Confirm that initialization succeeded before running incremental reconstruction.

if isInitialized(sfmObj)
    sfmObj = reconstruct(sfmObj);
end

Retrieve Results

Retrieve the estimated camera poses and the sparse 3-D point cloud.

camPoses = poses(sfmObj);
sparsePoints = pointCloud(sfmObj);

Visualize Reconstruction

Display the reconstructed scene showing the camera trajectory and sparse point cloud. Adjust the view orientation and zoom for better visualization.

plot(sfmObj,CameraSize=0.5,MarkerSize=25)
view(82.69,-15.53)
camroll(-90)
camva(4.52)

Input Arguments

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Structure from motion object, specified as an sfm object. The object must contain estimated camera poses and triangulated 3-D points generated by running triangulateInitialViews or reconstruct object functions.

Name-Value Arguments

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Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: plot(sfmObj,CameraSize=0.3,CameraColor=[0 0 1])

Camera base width, specified as a positive scalar.

Camera color, specified as an RGB triplet. An RGB triplet is a three-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

Marker size of the plotted 3-D points, specified as a positive scalar.

Control whether to display camera view IDs as labels, a logical 0 (false) or 1 (true).

Target axes for the plot visualization, specified as an Axes, UIAxes, or pcviewer (Point Cloud Toolbox) object. By default, the function plots into the current axes (gca). Use this name-value argument to visualize the plot in a UI for which you have specified Figure and Axes properties.

Version History

Introduced in R2026b

See Also

Objects

Functions