How It Works - SlimeDog/pHD Wiki
Vanilla HolographicDisplays shows holograms whenever a player is within the standard Minecraft view distance.
pHD replaces HolographicDisplays:LineTrackerManager with a modified version, in order to manage individual hologram visibility.
pHD does not modify the content of the holograms themselves.
pHD supports four hologram types, with different capabilities and uses.
Display is always subject to the optional restrictions, listed below. For example: a hologram cannot be viewed if the player does not have the required permission.
In most cases, the default values for distance and duration are used if specific values are not set. See Configuration. Type ALWAYS is a special case -- see the table below.
phd manage hologram_A ALWAYS distance 5.5
Display hologram_A whenever the player moves within 5.5 blocks of it. Use case: Create a secret hologram that is viewable only when very near to it. This is similar to a standard hologram, but with the view distance reduced to 5.5 blocks.
phd manage hologram_B NTIMES 3 distance 20
Display hologram_B whenever the player moves within 20 blocks of it, but only 3 times. After that, the player cannot see it. Use case: Create an instructional hologram at a spawn point, that the player sees the first 3 times it is encountered, and never again. Note that the player count can be reset by command. Restricting the acquisition distance helps ensure that the player actually sees the hologram.
phd manage hologram_C ALWAYS permission multiverse.portal.access.lobby_world
Display hologram_C whenever the player moves within the default view distance, if the player has the required permission. Use case: Create a portal hologram that is visible only if the player has the associated permission to use the portal.
Type ALWAYS options combinations
ALWAYS is a special case, depending on whether distance and duration options are specified or unspecified. The following table explains the effect of the various combinations on hologram activation and deactivation. In all cases, if a permission is specified, the player must have the required permission.