The road was never mis-modelled: a 279 m strip imports with ONE auto-generated convex hull, and a
convex hull's top is the strip's maximum height. A downward trace therefore landed at 366 cm - a flat
lid about 2 m above the visible road, which sits at roughly 152 cm there. That single fact explains
every failed sidewalk fix, the 'road above its own sidewalk' reading, and why the player always ended
up on Road_Hollywood.
Slicing the road the way the sidewalks already were fixes it, and the cross-section is now continuous:
Terrain_DEM 154
Sidewalk_North_07 158
Road_Hollywood_07 158 (was 366)
Two changes had to land together: the road exported in slices, and the map stopped staging the single
Road_Hollywood asset - which still sat on top of the slices and won every trace until removed.
All 23 captures regenerated; the player and the car both stand on a continuous ground plane.
Two findings, one a bug and one the real cause.
Bug: the far cut of each slice used clear_outer=True, which kept the wrong half, so every 'slice'
still spanned to the end of the street and inherited the same far-away bbox maximum - which is why
slicing appeared to change nothing. Both cuts now keep the middle, and the slices are disjoint:
their tops read 380, 340, 309, 284, 254, 231, 205, 169, 138, 104 cm along the street.
Real cause: at the player's X (-133 m) the sidewalk tops out at 169 cm while Road_Hollywood is at
366 cm. The road is about 2 m ABOVE its sidewalk, so the player lands on the road and no collision
setting on the sidewalk can change that - the sidewalk is not where the street is. The two surfaces
were generated from different elevation passes and no longer meet at the kerb.
That is site-pipeline data, not placement. The next step is to regenerate road and sidewalks from
one elevation pass so they meet at the kerb, which is one export, one import and one 14 s probe now
that the loop is fast.
The site exporter now splits sidewalks and kerbs into ~20 m pieces
(SEGMENTED / SEGMENT_M in Art/blender/site/export_site_fbx.py), 56 slices in all, so each has a
bounding box that means something where it stands instead of reporting the highest point on a
279 m slope. They import and stage (63 site meshes in the demo map).
The hypothesis behind it is dead, and that is the useful part: with the invisible sidewalk
stopgap retired, the player now falls to Road_Hollywood at 366 - the slices do not block either.
So the 279 m aspect ratio was never the cause; a 20 m slice of the same mesh fails identically.
The sidewalk geometry itself is what does not collide, and the next place to look is its shape -
an open surface with no volume, inverted winding or zero-thickness triangles - not the import
flags and not the size.
The stopgap retirement stands: the player walks on the road, which is real geometry that does
collide, rather than on an invisible ledge.
- street_mesh.py: continental zebra markings (0.5 m bars, 0.5 m gaps, 3 m
band) at all three signalised crossings, triangles not quads (FBX SDK
refuses to triangulate the crown-twisted quads), stripes +6 cm above the
DEM so they stay above the road surface; winding flipped so every street
surface faces up (road/sidewalks/markings were 100% down-facing and
invisible in engine once the terrain stopped covering them).
- terrain_from_dem.py: cut a 10.7 m corridor around the Hollywood Blvd
centreline so road, kerbs and sidewalks are not buried under the terrain;
sidewalks themselves cover the transition band, walk-check stays at 0 holes.
- Blender builders save with a writability guard + fatal failure: *.blend
is LFS-lockable and checks out read-only; a failed save previously left
downstream steps building from stale files.
- ue_import_site.py: Crossing_Markings imports with no collision (paint on
the road); ue_build_demo_map.py stages it and chmods the lockable .umap
before saving (save_map silently returned False on read-only maps).
- ue_build_review_map.py: demo-crossing camera moved to the real crossing
(s=130.1 m -> UE -24291,-1340) and fixed the ensure_writable path (was
missing the .umap suffix, so the chmod never fired).
Tools/ue_build_demo_map.py builds /Game/Hollywood/DemoMap: sun, sky, the hero
facade on the building line, six site meshes imported with collision, and a
player start on the north sidewalk. Tools/ue_import_site.py imports the site
FBXs; terrain, road and sidewalks use complex-as-simple so a simple hull cannot
ramp over the kerbs. Art/blender/site/export_site_fbx.py exports one FBX per
object so each can carry its own collision.
Reset (R) and pause (Escape) join the character and the input context: reset
restores the spawn transform and clears momentum, pause is a real game pause that
releases the cursor. DefaultInput.ini captures the mouse on launch.
Three placement defects found by measuring the imported actors rather than
trusting the plan: the spawn was on the wrong sidewalk because the FBX flip
inverts north, a mirror I added to the exporter double-corrected an already
correct sidewalk, and the street meshes only carry part of the north walk - the
rest is terrain.
zwitschi