Spatial Frame of Reference for Unity

This page describes the frame of references and coordinate systems (CS) used by Vuforia Engine. Use this information to orient your targets and content with respect to your device and the world coordinate system as the starting origin

There are three major frames of reference defined in the Vuforia Engine:

  • World: Defined as the start position of the device. This is your reference origin for the AR interaction.
  • Camera/Device: Origin on the physical device (or more precisely the camera position on the device). Camera/Device pose are reported in the World CS.
  • Target: Used for tracking physical objects or environment locations. Target poses are reported in the World CS, but the Up convention varies on the type of target.

Frame of Reference

In Unity, the coordinate system follows the DirectX convention (left-handed Y-up), and the poses are automatically applied to the scene objects.

  • World is left-handed, Y-Up, and gravity aligned.
  • Camera/Device is left-handed and Y-up.
  • Target varies:
    • Model Targets depend on the original model. The X axis is flipped in direction to conform to the left-handed coordinate system convention.
    • Other targets are left-handed and Y up.

Set the World Center Mode

The world origin (0,0,0) can be set to a specific target, to the first target detected, or to the device/camera. The setting is part of the AR Camera GameObject under World Center Mode.

FIRST_TARGET sets the world origin to the first detected Vuforia target. The target is from this moment maintaining its relative position and the AR Camera updates its transform position relative to the target. Other Vuforia targets and digital content are then relative to this first detected target.

SPECIFIC_TARGET sets the world origin to a specified target’s Observer Behaviour present in the Unity scene. Once the Vuforia target is detected, the world origin is set to it and the AR Camera and other content will update their position relative to the specified target.

DEVICE sets the world origin to the AR Camera GameObject. The AR Camera will then maintain a fixed position and the Vuforia targets and content will update their relative position with respect to it. This is for example necessary on eyewear devices.

When you have Track Device Pose enabled and the World Center Mode set to a FIRST or SPECIFIC target, disabling Track Device Pose will make the origin valid only for as long as the target is tracked.

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