Is it possible to get the orientation relative to the north?

Hi,

after reading sensor data and adapting them to your local coordinate system you have a transformation matrix. You then apply this transformation to any vector you want. Just use a vector to whatever north means to you.

E.g. I define north to be looking straight at the negative z-axis (I use a left-handed coordinate system), so my 'north' vector is (0, 0, -1)

You may want to look at the relvant method of my camera class. Some details concerning other classes of my framework are missing, but I think you can get the idea. Look at the calculation of 'finalForward' in the code.

void Camera::recalcOVR(XApp &xapp) {
	// now do it the oculus way:
	// Get both eye poses simultaneously, with IPD offset already included. 
	ovrVector3f useHmdToEyeViewOffset[2] = { xapp.EyeRenderDesc[0].HmdToEyeViewOffset, xapp.EyeRenderDesc[1].HmdToEyeViewOffset };
	ovrPosef temp_EyeRenderPose[2];
	ovrHmd_GetEyePoses(xapp.hmd, 0, useHmdToEyeViewOffset, temp_EyeRenderPose, NULL);

	for (int eye = 0; eye < 2; eye++)
		{
		ovrPosef    * useEyePose = &xapp.EyeRenderPose[eye];
		float       * useYaw = &xapp.YawAtRender[eye];
		float Yaw = XM_PI;
		*useEyePose = temp_EyeRenderPose[eye];
		*useYaw = Yaw;

		// Get view and projection matrices (note near Z to reduce eye strain)
		Matrix4f rollPitchYaw = Matrix4f::RotationY(Yaw);
		Matrix4f finalRollPitchYaw = rollPitchYaw * Matrix4f(useEyePose->Orientation);
		// fix finalRollPitchYaw for LH coordinate system:
		Matrix4f s = Matrix4f::Scaling(1.0f, -1.0f, -1.0f);
		finalRollPitchYaw = s * finalRollPitchYaw * s;

		Vector3f finalUp = finalRollPitchYaw.Transform(Vector3f(0, 1, 0));
		Vector3f finalForward = finalRollPitchYaw.Transform(Vector3f(0, 0, -1));
		Vector3f Posf;
		Posf.x = pos.x;
		Posf.y = pos.y;
		Posf.z = pos.z;
		Vector3f diff = rollPitchYaw.Transform(useEyePose->Position);
		Vector3f shiftedEyePos;
		shiftedEyePos.x = Posf.x - diff.x;
		shiftedEyePos.y = Posf.y + diff.y;
		shiftedEyePos.z = Posf.z + diff.z;
		look.x = finalForward.x;
		look.y = finalForward.y;
		look.z = finalForward.z;

		Matrix4f view = Matrix4f::LookAtLH(shiftedEyePos, shiftedEyePos + finalForward, finalUp);
		Matrix4f projO = ovrMatrix4f_Projection(xapp.EyeRenderDesc[eye].Fov, 0.2f, 2000.0f, false);
		Matrix4fToXM(this->viewOVR[eye], view.Transposed());
		Matrix4fToXM(this->projOVR[eye], projO.Transposed());
	}
}

If you are referring to compass directions as in "Earth magnetic north" then no, the SDK doesn't supply that type of sensor fusion.