isInitialized

R2026b

Determine if 3-D reconstruction has been initialized for structure-from-motion (SfM)

Since R2026b

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Syntax

tf = isInitialized(sfmObj)

Description

tf = isInitialized(sfmObj) returns a logical value indicating whether the initialization of 3-D reconstruction for has been successful for the sfm object sfmObj. To initialize 3-D reconstruction for an sfm object, use the triangulateInitialViews object function. Use the isInitialized function to verify whether the sfm object is ready for incremental 3-D reconstruction before calling the reconstruct 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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Initialization status of structure from motion sfm object, returned as a logical 0 (false) or 1 (true). A value of true indicates that the 3-D reconstruction for the sfm object has been initialized using the triangulateInitialViews object function, which triangulates the first 3-D scene points using the best initial view pair.

Data Types: logical

Version History

Introduced in R2026b

See Also

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