Setting world scale without affecting physics

Hi,
I want to be able to scale up / down the scale of AR scene. How can I setup the scale for a whole AR scene without affecting physics? When I set scale of root GameObject it breaks physics (wheel colliders).

Thanks

 

Great question! I just gave a talk about this last week at Unite Austin. The talk and sample code will be posted next week, but the short answer is: do not scale your content (because physics will be affected, for example); instead scale all positional information coming from the device. This includes the position of the camera, the plane positions, boundaries, and extents. The easiest way to do this is to put the camera and all GameObjects generated by the device (e.g. TrackedPlanes) under the same parent GameObject, and apply scale to that. So your hierarchy might be

AR Root

Camera [Components: TrackedPoseDriver, SessionComponent]
AR Controller [Components: HelloARController]
​

If you then scale the "AR Root" GameObject, then it should scale the camera and visual representation of the planes. Note, however, that it hit tests within ARCore won't be aware of the scale, so you'll need to remove the scale from your raycast input and then rescale the result.

Hope that makes sense! Let me know if you have any questions.

Cheers,
Tim

 

Quick follow-up question. Does the local positions / rotations of the Camera and ARController matter before trying this scaling method? Do they need to be at [0,0,0] and identity?

 

For the camera, that depends on whether you check the "Use relative transform" checkbox on the TrackedPoseDriver. If it is checked, then it remembers the initial position+rotation ("pose") and makes the final pose relative to that initial pose.

For the ARController, the HelloARController spawns in plane prefabs using itself as the parent, so its position+rotation would also matter.

 

Let me just clarify: the initial position+rotation matters because it affects things in the way I mentioned above, but scale should still work (fingers crossed; I haven't tried this specific setup).

 

Hi @timmunity

You said 'The talk and sample code will be posted next week' have you a link to this please, thanks.

 

There's a blogpost here explaining how it works and includes a link to the Unite talk.
https://blogs.unity3d.com/2017/11/16/dealing-with-scale-in-ar/

All sample code can be found here:
https://github.com/Unity-Technologies/experimental-ARInterface

 

Thank you, very helpful ..

 

Ha, thanks for this. Got myself in a right pickle scaling content and (attempting to) correct for physics with our first play with ARCore a few months back.

 

Here is a forum post that describes how to achieve this with AR core preview 2 : https://forum.unity.com/threads/ar-scale-in-arcore-preview-2-tutorial.512009/

 

Just a note - https://github.com/Unity-Technologies/experimental-ARInterface has been updated for ARCore preview 2 and the latest ARKit plugin as well. Scale still works.

 

Hello, I was searching for this ARController and it turned out it is in this repo: https://github.com/Unity-Technologies/experimental-ARInterface but it is saying that there is no support for this anymore - deprecated. Do you have any other suggestions about scaling down in AR? Thank you in advance!

 

The equivalent is ARSessionOrigin in ARFoundation. You might also want to check out this forum post on scale.