Flight volumes

Agents that fly or swim are not bound to the ground, so a navmesh does not describe where they may go. A flight volume (maul-nav/flight.h) does: each tile is a sparse voxel octree of the space a flier's center may occupy. It is baked from the same input as the navmesh, and streamed and committed the same way.

The def

mnavDefaultFlightDef gives 1 m voxels, tiles of 32 voxels, a volume from 0 to 64 m and a flier 0.5 m in radius. Then set:

• The voxel size and tile side. A tile's side is 4 times a power of 2, from 16 to 512 voxels. Smaller voxels thread narrower gaps and cost more memory.
• The floor and ceiling, in meters from the origin. Fliers never leave this range: a point below or above it given to mnavFlightVolume_IsOpen or a flight path search is mnav_errorOutside.
• The radius. The flier is a sphere: every voxel within its radius of something solid is closed to its center. A long, flat flier takes the sphere that holds it.
• enableGroundFill. On, the space under each column's lowest solid voxel is solid too, so the space beneath a terrain is not open. Turn it off for open space, such as a field of floating debris, where it would fill below every floating piece.

mnavValidateFlightDef checks a def without making anything and names the first bad setting.

Baking and loading

• mnavCreateFlightBaker, then mnavFlightBaker_BakeTile with the same mnavBakeInput a navmesh bake takes, then mnavFlightBaker_CopyTile. A voxel any triangle touches is solid. Triangles are surfaces: the inside of a closed mesh stays open space, which no path from outside reaches. A search for an end in such a space gives mnav_pathNone with the start alone at once when the space holds at most 512 blocks and no more than the query's node limit (mnavQueryLimits.nodes); a larger one is searched until the node budget runs out, so keep path ends out of closed meshes. Tiles are independent calls, give the same bytes on every platform, and carry a fingerprint as navmesh tiles do.
• mnavCreateFlightVolume from a flight volume def (mnavDefaultFlightVolumeDef): its allocator, its limits on tiles and memory, and in flight the def its tiles are baked with. Then mnavFlightVolume_StageTile and mnavFlightVolume_StageTileRemoval, then mnavFlightVolume_Commit. Every byte is checked as hostile input, and a tile baked with other settings is refused. mnavFlightVolume_GetTile reads a committed tile's fingerprint.
• A world with fliers bakes each tile twice: once at the navmesh's cells, once at the flight volume's voxels.

Queries

• mnavFlightVolume_IsOpen tells whether a point is open to the flier.
• mnavFlightVolume_FindNearestPoint finds the nearest open point within a radius. Snap a path's ends with it first.
• mnavQuery_FindFlightPath finds a path in an mnavQuery context, under its node budget and path length limit. Its points are each in sight of the next, so the flier flies straight between them.
• mnavQuery_BeginFlightPath, mnavQuery_ContinueFlightPath and mnavQuery_FinishFlightPath run the same search a number of nodes at a time, to spread a long search over frames; the path is the one mnavQuery_FindFlightPath gives. A commit between slices makes the search stale: begin again.
• mnavFlightVolume_Raycast stops at the first blocked voxel, the floor or ceiling, or a place with no tile.
• mnavFlightVolume_CheckPath casts a path's steps in order and names the first one blocked or with no tile. After a commit, check what is left of each path being followed, from where the flier is, and search again when a step fails.

Fliers avoid each other with mnavAvoidance_Avoid3D; see crowds.