According to the spec document in 18.104.22.168, the directional lightpoint must be oriented by client based on A01 vector attribute.
ok, so the normal is "north" based (y axis) and no component in z axis. Just surprise that there is no way to model a light point with the Z axis (for example if you would want to model a directional light at the bottom of a skyscraper just pointing up to illuminate the wall of the skyscraper).
I am trying to figure out what should be the direction vector for a "Directional" light point in CDB? if it (0.0f, 0.0f, 1.0f) or (0.0f, 1.0f, 0.0f), or (1.0f, 0.0f, 0.0f) ???