Resolved Confused about how snapshots work

1- Yes, without an authoring component on the prefab, it is not considered a ghost.
2- The GhostComponent and GhostField are two completely different things and yes, you can have both of them declared. The GhostField MUST be used to mark the component fields that should be serialized. The GhostComponent on the other end, allow you to specify to which Ghost type should be replicated to (Predicted, Interpolated), if Server/Client only and other things.
3 - The GhostField must be added to a component that need be replicated. Without ghosts fields, a component is not considered replicated. It is not mandatory to mark all fields as replicated. You may have a dependent field witch value can be recomputed by using other replicated data for example. Or a field that is only used by the server/client during the simulation and that not need to be replicated (this is more rare)
4 - Yes, if something is used inside the prediction loop you must in general add the GhostField for it. Otherwise, when the entity state is rollback to the server state, some component data are not restored correctly and the simulation prediction can be completely wrong.
5 - The GhostComponentAuthoring is used to configure the prefab ghost. The GhostComponent just provide the default for how a component should be handled by the different ghost type and mode. The GhostComponentAuthoring overrides the GhostComponent (where possible)
6- I didn't understood exactly what you meant for synchronization, but Predicted-Interpolated behaviour are mutually exclusive at the moment. It is possible eventually to configure at spawn time the behavior of ghost if the SupportedGhostMode is set to ALL (but require some user logic).

 

The name are a little confusing probably. We need to clarify better that section.

There are two type of ghosts: Interpolated and Predicted. When you configure a prefab you specify what mode is using.
A component may be added to different type of ghost prefab in general. And based on the modality, it may be enabled/disabled as necessary or not to sent to the client.
For example: there may be components that are necessary only if the ghost is a predicted one (because the client also run the server logic) but that on a interpolated ghost may be completely useless (because no simulation is running).
The InterpolatedClient, PredictedClient allow you to specify for witch ghost mode the component should be serialized to the client and/or present on the entity. Based on the configuration, the component can be stripped from the prefab and or removed after a ghost is spawned.

If the ghost is predicted, it present a PredictedGhostComponent. The prediction logic is usually the same the server already does, and must be inside the PredictedGhostSystemGroup.
Note also that on the server there is no distinction in between predicted or interpolated. All ghosts are "predicted", meaning that they have a PredictedGhostSystemGroup are all simulated inside the PredictedGhostSystemGroup.

 

NetCode does not support adding / removing component at runtime (they will not be synced). And yes, if you add / re-add a component it will not be stripped.

 

We are planning to use that feature in the future for disabling components and simplify other bits. In particular also, we are planning to use enable bits for replicating tags. We don't have any reasonable timeline/roadmap for that yet (since the enable bit feature is still in development).