ludic/packages/ludic.nav

ludic.nav

A walkable mesh of the world and the ways across it, over Recast & Detour (zlib) built here from a pinned tag (phase 17). Uses ludic.base and nothing else.

import "ludic.nav"

The rules it keeps

• One mesh per kind of walker. NAV_PERSON (0.35 m wide, the hiker's 0.55 m step), NAV_LARGE (an elk, a bear, a horse) and NAV_SMALL (a hare, a marmot) each have their own, because what a hare slips between a bear walks round. A NavConfig says what a mesh is built for: its voxels and its walker's height, radius, step and steepest slope.
• Built from triangles, or loaded from a bake. nav_build rasterizes triangles - each with an area byte, 0 not walkable and 1..62 a kind of ground - and marks every cylinder given (a trunk, a post) as somewhere nothing stands; ground steeper than the slope is cleared whatever its area. A game bakes its maps once and loads the bytes (nav_save_file / nav_load_file): a map is never built at start-up.
• A path is corners. nav_path answers the way from one point to another as the corners where it turns, the first the start and the last the end. When the end cannot be reached the path stops as near it as the mesh allows and nav_partial says so - a walker goes there and gives up, never through a river. Either end off the mesh is -1.
• A kind of ground has a cost (nav_area_cost): a trail cheaper than a meadow, scree dearer.
• The same question gets the same answer. Detour is deterministic for the same mesh and the same points, so co-op's order of dice is untouched by asking it.

API

NAV_PERSON, NAV_LARGE, NAV_SMALL, NAV_CORNERS	the kinds of walker, and a path's most corners (256)
NavConfig { cell, cell_h, height, radius, climb, slope }	what a mesh is built for (a person by default)
nav_build(kind, v, nv, t, nt, area, cyl, nc, config) -> bool, nav_polygons(kind)	a mesh from triangles and cylinders (x, y, z, r, h each)
nav_save_file(kind, path), nav_load_file(kind, path), nav_reset()	a baked mesh written and read; every mesh let go
nav_nearest(kind, x, y, z) -> bool, nav_near_x/y/z()	the nearest walkable point within a couple of metres
nav_path(kind, sx, sy, sz, ex, ey, ez) -> int, nav_corners(), nav_corner_x/y/z(i), nav_partial(kind)	a way as corners
nav_straight(kind, sx, sy, sz, ex, ez) -> bool	does the straight line stay walkable
nav_area_cost(kind, area, cost)	how dear a kind of ground is to cross

Tests

ludic test packages/ludic.nav

A 40 m meadow built by hand: a path round a post, over a river's ford, stopping at the bank of a river with none, the nearest point, and a saved mesh answering as the built one did.

The native library

native/build.sh fetches Recast & Detour v1.6.0, checks its SHA-256, and builds Recast, Detour and the shim (native/shim/nav_shim.cpp) into lib/<target>/ - the same script on the Mac and on the PC (Git Bash, the LLVM installer's clang). native/LICENSE-recastnavigation ships with it.