EGroundChangeWhat

What a journal entry may have changed (FGroundChange::What), as bits: a may-have-changed set, so a reader that caches one kind of data skips the entries without its bit.

Declaration

enum class EGroundChangeWhat : uint16_t

Header: #include "Native/GroundJournal.h"
Module: PublicDependencyModuleNames.Add("OrreryTerrainCore"); in your module’s Build.cs.
Stability: Stable: changes within a major version only add.
Thread: Every reader pulls the same entries with its own cursor: any thread through FGroundQuery::ChangesSince, the far field through FTerrainWorld::FarChanges. (the header’s rule)

Description

The publish that makes an entry sets the bits by its cause: Commit and Undo set Heights, Holes and GroundClass; HostImport sets Heights, Paint and GroundClass; Extension sets Heights, Paint, GroundClass and Cover; Stream sets Residency. A sculpt publish (a brush run, a stroke's end, a stroke's undo or redo, a patch or a repair) sets only what its changes moved: Heights when a post moved; Paint for a paint or paint-layer channel; GroundClass for the ground-class channel, with Holes when a hole cell was painted or cleared; and Holes and GroundClass when its re-bake changed a feature's hole cells (a tunnel face over sculpted ground). A publish that changed the feature stack adds an entry of its own with Features alone, and a far entry (FGroundChange::Levels != 0) sets Heights (FGroundChange).

Append-only: a later version may add bits above Residency, and a reader ignores the bits it does not know.

Values

Value	Meaning
`None` = 0	—
`Heights` = 1u << 0	Heights of the ground (Modified, and Natural for a sculpt).
`Paint` = 1u << 1	Paint: the paint slot planes (`Channels::PaintSlotLayerFirst`.., PaintSlots.h).
`GroundClass` = 1u << 2	Ground class, and so the physical material.
`Holes` = 1u << 3	Hole cells: a tunnel's opening.
`Features` = 1u << 4	The feature stack: features added, replaced or removed, and what derives from them (walls), over their tiles.
`Cover` = 1u << 5	An extension's cover layer (`ESurface::Top`).
`Water` = 1u << 6	The water surface (`ESurface::Water`). Reserved: nothing sets it yet.
`Residency` = 1u << 7	Tiles became resident or left: the answers of residency-dependent reads changed, not the truth.