This allows specifying how many times per second an effect should be
triggered for a particle source instead of triggering the effect every
frame. This will allow modders to achieve more consistent particle
effects regardless of FPS.
Previously, the source orientation was always aligned to the world so it
couldn't adapt to a weapon that changes direction. This fixes that by
introducing a "relative" mode for source orientations that is enabled by
default and disabled if the direction is set explicitly.
asarium