isConnected

R2026b

Determine if image views are connected to form view graph for structure-from-motion (SfM)

Since R2026b

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Syntax

tf = isConnected(sfmObj)

Description

tf = isConnected(sfmObj) returns a logical value indicating whether a visual similarity-based view graph connecting the images associated with the sfm object sfmObj exists. To create a view graph which connects the unordered image collection associated with an sfm object, use the connectImagePairs object function. Use the isConnected function to verify whether the view graph is ready for refinement before calling the verifyImagePairs function.

example

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.

Output Arguments

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View graph existence status for the sfm object, returned as a logical 0 (false) or 1 (true). A value of true indicates that the view graph created by the connectImagePairs function is stored in the ViewGraph property of the sfm object.

Data Types: logical

Version History

Introduced in R2026b

See Also

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