tools/fetch_dem.py pulls the open AWS terrarium elevation tiles for each
level's bbox (derived from the OSM geometry itself -- the fetch bboxes were
never recorded) and writes an f32 heightmap. The builder bilinear-samples it:
roads/footpaths/crossings drape (subdivided to ~8 m so long OSM segments stop
chording across curved ground), buildings lift rigidly to the lowest terrain
under their footprint with a 2 m foundation skirt, trees/props/planters ride
their own base heights, and the flat ground slab becomes a real terrain mesh.
Bridges get an explicit deck profile (lerp between end heights plus a hump)
instead of draping down into the river, the truss follows the deck, and the
Bradfield Highway now genuinely flies over Kemp Place -- the game has an
underpass. Kangaroo Point's cliffs are an actual 20 m drop, Edward Street
climbs to 55 m at Spring Hill.
Junction events bake spawn/convoy heights (osm_junction.py grew a pure-python
DEM sampler); the game respects marker heights everywhere it used to hardcode
ground=0.
Bugs the terrain surfaced, all found by measurement:
- Long road segments chorded across curved ground: the car visually sank to
its windows mid-block. Fixed by subdividing draped ribbons.
- The 9 m terrain grid aliases cliff edges and bulged metres ABOVE the finely
draped roads: a car spawning there was inside the terrain sheet and got
depenetrated through the floor into the void (y = -710). Fixed by giving
roads real collision and carving the terrain grid down wherever a draped
road sample lands (11k+ carve samples on Kangaroo Point alone).
- The junction validator and tuner drove throttle-only, which cross-slope
drift turned into 40-86 m misses; they now hold aim like a player would.
- Edward x Elizabeth launched down a 17% grade, went airborne at the crest
and wedged off-street: unwinnable geometry, not a bug. Swapped for
Elizabeth x George on the flat lower CBD. All 9 junctions validate.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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