XRInputSource: gripSpace property

An XRSpace object representing the position and orientation of the input device in virtual space, suitable for rendering an image of the device into the scene. gripSpace is null if the input source is not inherently trackable. For example, only inputs whose targetRayMode is tracked-pointer provide a gripSpace.

Imagine that the controller is shaped like a straight rod, held in the user's fist. The native origin of the grip space is located at the centroid—the center of mass—of the user's fist, tracking the position of the user's hand.

The coordinate system for the left hand's grip space.

The coordinate system for the right hand's grip space.

As shown in the diagram above, the coordinate system is oriented as follows:

• The x-axis is perpendicular to the palm of the user's hand, with the direction extending outward from the back of the hand being +X if the controller is in the user's right hand or -X if the controller is in the left hand.
• The z-axis along the length of the rod, parallel to the user's palm and along the length of their grip. -Z is in the direction of the user's thumb, and +Z is in the opposite direction.
• The y-axis is implied by the relationship between the other two axes; as is always the case, it's the cross product of the other two axes (lying 90° away from both the X and Z axes).

In tis example, taken from the frame rendering callback, the gripSpace is used to render a mesh that represents the position and orientation of the controller in the virtual environment.

for (const source in xrSession.inputSources) {
  if (source.gripSpace) {
    const gripPose = frame.getPose(source.gripSpace, xrRefSpace);

    if (gripPose) {
      myDrawMeshUsingTransform(controllerMesh, gripPose.transform.matrix);
    }
  }
}

For each input source which has a value for gripSpace, this loop obtains the XRPose representing the position and orientation that are described by gripSpace. If a valid pose is returned, a method myDrawMeshUsingTransform() is called to draw the controller's mesh transformed using the grip pose's transform matrix.