Get Camera Translation from ARCamera

Question

I am experimenting with Apple's ARKit and have a question regarding camera transformations. Which of the values in the transform matrix represent how far the user has travelled from the point of origin? Calling

self.sceneView.session.currentFrame!.camera.transform.columns.0.x

does not seem to yield the correct X translation.

Additionally, what would be the correct location for Y and Z?

score 6 · Accepted Answer · answered Jun 30 '17 at 05:39

6

The last column of a 4x4 transform matrix -- matrix.columns.3 in this case -- is the translation vector. See this old answer for some background on 4x4 transform matrices and how they work.

answered Jun 30 '17 at 05:39

rickster

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1

Your SO answers have been extremely helpful during my ARKit work, thank you. – Hunter Monk Dec 21 '17 at 00:55

score 1 · Answer 2 · answered Sep 01 '18 at 10:35

The simplest way to get ARCamera's translation is the following:

func getCameraTransform(for sceneView: ARSCNView) -> MDLTransform {
    guard let transform = sceneView.session.currentFrame?.camera.transform else { return }
    return MDLTransform(matrix: transform)
}

let position = SCNVector3(cameraTransform.translation.x, 
                          cameraTransform.translation.y, 
                          cameraTransform.translation.z)

gaurav_mobile · Answer 3 · 2021-05-08T05:22:48.053

1

func session(_ session: ARSession, didUpdate frame: ARFrame)
 {
     // Do something with the new transform
     let currentTransform = frame.camera.transform
     let x = currentTransform.columns.3.x
     let y = currentTransform.columns.3.y
     let z= currentTransform.columns.3.z
 }

The last column of vector is translation values. you can get translated values from column 3

edited May 08 '21 at 05:22

answered Feb 18 '19 at 09:20

gaurav_mobile

31
8

add some explanation referring to this block – Ivan Aracki Feb 18 '19 at 09:48

Get Camera Translation from ARCamera

3 Answers3