The rotation value on the Scene Root inspector is incorrect

[inkyaman]

I am making a system using this project in my graduation training.I want to shift the display on the wall plane vertically in the direction of the camera.Since I found that the plane object was placed relative to the SceneRoot, I thought that if I could get the value of the SceneRoot in world coordinates, I could convert the camera position to local coordinates relative to the SceneRoot.

However, when I unchecked run on device, inserted
・Debug.Log (SceneRoot.transform.Rotation)
into the script, and ran the demo on the Unity editor, the SceneRoot rotation value displayed on the console and in the inspector the SceneRoot rotation values displayed on the inspector were different.

In the console, the value of transform.EulerAngle was (0.0, 0.0, 0.0)

Since I have run on device turned off, I think the sceneToUnityTransform matrix, which sets the SceneRoot to world coordinates, is still initialized with 0, but what exactly is this happening?

[SzymonSPS]

I'm not 100% sure I understand your question so allow me to re-state it.

You're trying to understand the relative transform of the camera (head) and a plane. The scene root should be static, so on PC the origin of the scene is 0,0,0, on a device it's 0,0,0 but also attached to an anchor. The transform of your head should be the camera transform, so you should be able to compute the transform between the camera matrix and the wall transform matrix.

Do I understand your question? Does this help?

[SzymonSPS]

Also, please move to the latest sample, https://github.com/microsoft/MixedReality-SceneUnderstanding-Samples which should help as it's the one we're actively supporting/maintaining.

[inkyaman]

Thanks for the reply.
I'm not currently running on HoloLens 2, and I'd like to ask you about a problem with the demo on your PC.
Perhaps the SceneRoot defined in SceneUnderstandingDisplayManager.cs is located in Unity space with the function on line 262 below.

TransformUtils.SetUnityTransformFromMatrix4x4 (sceneToUnityTransform.Value, SceneRoot.transform);

At this time, on the PC demo, I think that the SceneRoot is placed at the 0,0,0 position and the 0,0,0 EulerAngle in the SetUnityTransformFromMatrix4 × 4 function of TransformUtils.cs. However, when I looked at the inspector of the Root object of the hierarchy, the position was certainly 0,0,0, but the Rotation was like -51,40, -75, so I wondered why.

Also, regarding the latest sample, there are not many review articles in Japanese, and I could not understand the specifications by myself, so I decided not to use it. I'm sorry. (I couldn't even run the demo on my PC.) The version I'm currently using is sufficient for the function, and I can understand the script to some extent, so I'd like to use this while solving the above problem.

[SzymonSPS]

This makes sense. If you need help getting the new sample running on PC I can get you in touch with someone to help. I understand language may be a problem, but we're happy to try and want to understand.

I don't know why the rotation is -51.4,-75 as it has been a while, potentially we align the floor to be facing up? Since the data was captured on a HL2, we may need to correct for gravity, this is only a guess.

Regardless, the transform between camera and plane should be the correct way to get what you want, since it's rendering in unity correctly and at this point you are essentially just working in a normal unity scene. Scene Understanding was used to generate the initial scene, but now you are in standard unity to some extent.