The tracer source is perpendicular to the direction it's travelling and the direction of the camera.
The tracer source is aligned with the local Z-axis, which is detenmined by the rotation of the node that emits the tracer.
The tracer source is aligned with the global vertical axis.
The tracer source is aligned with the global X-axis.
The tracer source is parallel to the global diagonal (1, 1, 1).
Values representing different orientation modes for Tracer and LegacyTracer particles.