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gig-line/Art/blender/street/street_mesh.py
T
zwitschi cef87b3d31 street: continental zebra markings at the three signalised crossings
0.5 m white bars with 0.5 m gaps across a 3 m band per crossing, laid
1 cm above the road surface. Makes the mid-block crossing (OSM way
385648319, s=130.1 m) a designated crossing in game. Metadata audit
passes (1 sidecar, 0 problems).
2026-11-07 15:24:21 +01:00

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"""Build the street corridor — road, kerbs, sidewalks — on the DEM.
B=/var/lib/flatpak/app/org.blender.Blender/x86_64/stable/active/files
LD_LIBRARY_PATH="$B/blender/lib" "$B/blender/blender" -b --factory-startup \
--python Tools/street_mesh.py -- \
--osm Geo/raw/osm-api-map-2026-11-06.osm \
--dem Geo/raw/dem-3dep-1m-26911-2026-11-06.tif \
--out Art/blender/street/street-2026-11-06.blend
Everything lands in the project frame from `Geo/manifests/local-origin.md`:
X east, Y north, Z up, metres, origin at Hollywood × Highland.
Geometry follows the measured profile rather than a guess:
* carriageway between gutters at ±10.5 m from the centreline (cross-sections
put them at −10 and +10…+12; the crossing length says 20.9 m);
* kerb upstand **0.15 m**, which is an assumption — the DEM does not resolve a
kerb (see `Geo/verification/2026-11-06-cross-sections.md`);
* kerbs are flushed to 0.02 m within ±2.5 m of each signalised crossing, with a
1.5 m blend, so the crossings are actually usable on foot;
* each signalised crossing gets continental zebra markings — 0.5 m white bars
with 0.5 m gaps across a 3 m band, laid 1 cm above the road surface — so the
mid-block crossing (OSM way 385648319, s ≈ 130 m) reads as a designated
crossing in game;
* sidewalk widths 4.0 m south and 5.3 m north, from the DEM-derived setback
arithmetic;
* the DEM supplies every elevation, so the 3.4 m fall and the ~2 % crown come
through unchanged.
The road surface is lifted 2 cm above the DEM so it does not z-fight the terrain
mesh. When the terrain is cut to the corridor later, that lift can go.
"""
import argparse
import glob
import math
import os
import shutil
import subprocess
import sys
import bpy
HERE = os.path.dirname(os.path.abspath(__file__))
sys.path.insert(0, os.path.join(HERE, "..", "..", "..", "Geo", "tools"))
import dem_stats # noqa: E402
import osm_common as oc # noqa: E402
ORIGIN_E = 376515.389
ORIGIN_N = 3774224.083
ORIGIN_Z = 115.911
SOUTH_GUTTER = -10.5
NORTH_GUTTER = 10.5
SOUTH_SIDEWALK = -14.5
NORTH_SIDEWALK = 15.8
CROSSINGS = (36.6, 130.1, 266.1)
def parse_args():
argv = sys.argv
argv = argv[argv.index("--") + 1:] if "--" in argv else []
ap = argparse.ArgumentParser()
ap.add_argument("--osm", required=True)
ap.add_argument("--dem", required=True)
ap.add_argument("--out", required=True)
ap.add_argument("--along", type=float, default=1.0)
ap.add_argument("--cross", type=float, default=0.75)
ap.add_argument("--kerb", type=float, default=0.15)
ap.add_argument("--ramp-half-width", type=float, default=2.5)
ap.add_argument("--ramp-blend", type=float, default=1.5)
return ap.parse_args(argv)
def find_proj():
env = os.environ.get("PROJ_BIN")
if env and os.path.exists(env):
return env
which = shutil.which("proj")
if which:
return which
matches = sorted(glob.glob(os.path.expanduser(
"~/.local/share/flatpak/app/org.qgis.qgis/x86_64/stable/*/files/bin/proj")))
if not matches:
raise SystemExit("no PROJ binary; set PROJ_BIN")
return matches[0]
def project_to_utm(points, proj_bin):
app_files = os.path.dirname(os.path.dirname(proj_bin))
env = dict(os.environ)
env["LD_LIBRARY_PATH"] = f"{app_files}/lib:{env.get('LD_LIBRARY_PATH', '')}"
payload = "\n".join(f"{lon:.9f} {lat:.9f}" for lat, lon in points) + "\n"
out = subprocess.run([proj_bin, "+proj=utm", "+zone=11", "+datum=NAD83", "-f", "%.4f"],
input=payload, capture_output=True, text=True, env=env, check=True)
return [tuple(float(v) for v in line.split()) for line in out.stdout.strip().splitlines()]
class Dem:
def __init__(self, path):
entries, w, h, values = dem_stats.read_tiff(path)
self.w, self.h, self.v = w, h, values
scale, tie = entries[33550], entries[33922]
self.x0 = tie[3] - tie[0] * scale[0]
self.y0 = tie[4] + tie[1] * scale[1]
self.sx, self.sy = scale[0], scale[1]
nodata = entries.get(42113)
self.nodata = float(nodata) if nodata not in (None, "") else None
def at(self, e, n):
col = (e - self.x0) / self.sx - 0.5
row = (self.y0 - n) / self.sy - 0.5
c0, r0 = int(col // 1), int(row // 1)
if c0 < 0 or r0 < 0 or c0 + 1 >= self.w or r0 + 1 >= self.h:
return None
fx, fy = col - c0, row - r0
p = []
for r, c in ((r0, c0), (r0, c0 + 1), (r0 + 1, c0), (r0 + 1, c0 + 1)):
val = self.v[r * self.w + c]
if self.nodata is not None and val == self.nodata:
return None
p.append(val)
return (p[0] * (1 - fx) * (1 - fy) + p[1] * fx * (1 - fy)
+ p[2] * (1 - fx) * fy + p[3] * fx * fy)
def kerb_height(s, base, half_width, blend):
"""Full kerb, except flushed near a crossing so people can step off."""
for crossing in CROSSINGS:
d = abs(s - crossing)
if d <= half_width:
return 0.02
if d <= half_width + blend:
t = (d - half_width) / blend
return 0.02 + (base - 0.02) * t
return base
def strip(rows, offsets, z_at, name, material):
"""Build a quad grid from per-row sampled vertices."""
verts, faces = [], []
cols = len(offsets)
for r, (_s, base, normal) in enumerate(rows):
for off in offsets:
x = base[0] + off * normal[0]
y = base[1] + off * normal[1]
verts.append((x, y, z_at(r, off, x, y)))
for r in range(len(rows) - 1):
for c in range(cols - 1):
i = r * cols + c
faces.append((i, i + 1, i + cols + 1, i + cols))
mesh = bpy.data.meshes.new(name)
mesh.from_pydata(verts, [], faces)
mesh.update()
if material:
mesh.materials.append(material)
obj = bpy.data.objects.new(name, mesh)
bpy.context.scene.collection.objects.link(obj)
return obj
def main():
args = parse_args()
nodes, ways = oc.load(args.osm)
line, _, _, _, block_len = oc.block_extent(
nodes, ways, "Hollywood Boulevard", "North Orange Drive", "North Highland Avenue")
utm = project_to_utm(line, find_proj())
local = [(e - ORIGIN_E, n - ORIGIN_N) for e, n in utm]
# arc length + unit normals in the local frame
acc, lengths = 0.0, [0.0]
for a, b in zip(local, local[1:]):
acc += math.hypot(b[0] - a[0], b[1] - a[1])
lengths.append(acc)
total = lengths[-1]
print(f"centreline {total:.1f} m")
def at(s):
for i in range(len(local) - 1):
if lengths[i] <= s <= lengths[i + 1]:
seg = lengths[i + 1] - lengths[i]
t = 0.0 if seg == 0 else (s - lengths[i]) / seg
ax, ay = local[i]
bx, by = local[i + 1]
dx, dy = bx - ax, by - ay
norm = math.hypot(dx, dy) or 1.0
return ((ax + t * dx, ay + t * dy), (-dy / norm, dx / norm), (dx / norm, dy / norm))
ax, ay = local[-1]
return ((ax, ay), (0.0, 1.0), (1.0, 0.0))
dem = Dem(args.dem)
rows = []
s = 0.0
while s <= total + 1e-9:
base, normal, tangent = at(s)
rows.append((s, base, normal))
s += args.along
# materials
asphalt = bpy.data.materials.new("Asphalt")
asphalt.diffuse_color = (0.09, 0.09, 0.095, 1.0)
concrete = bpy.data.materials.new("Concrete")
concrete.diffuse_color = (0.55, 0.53, 0.50, 1.0)
def dem_z(x, y):
z = dem.at(x + ORIGIN_E, y + ORIGIN_N)
return None if z is None else z - ORIGIN_Z
road_offsets = [SOUTH_GUTTER + i * (NORTH_GUTTER - SOUTH_GUTTER) / 28 for i in range(29)]
south_offsets = [SOUTH_SIDEWALK + i * (SOUTH_GUTTER - SOUTH_SIDEWALK) / 8 for i in range(9)]
north_offsets = [NORTH_GUTTER + i * (NORTH_SIDEWALK - NORTH_GUTTER) / 10 for i in range(11)]
def road_z(r, off, x, y):
z = dem_z(x, y)
return (z if z is not None else 0.0) + 0.02
def south_z(r, off, x, y):
z = dem_z(x, y)
base = z if z is not None else 0.0
return base + kerb_height(rows[r][0], args.kerb, args.ramp_half_width, args.ramp_blend)
def north_z(r, off, x, y):
return south_z(r, off, x, y)
road = strip(rows, road_offsets, road_z, "Road_Hollywood", asphalt)
sw_s = strip(rows, south_offsets, south_z, "Sidewalk_South", concrete)
sw_n = strip(rows, north_offsets, north_z, "Sidewalk_North", concrete)
# kerb faces: vertical quads joining road edge to sidewalk edge
def kerb_faces(offset, name):
verts, faces = [], []
for idx, (s_val, base, normal) in enumerate(rows):
x = base[0] + offset * normal[0]
y = base[1] + offset * normal[1]
z_road = road_z(idx, offset, x, y)
h = kerb_height(s_val, args.kerb, args.ramp_half_width, args.ramp_blend)
z_walk = (dem_z(x, y) or 0.0) + h
verts.extend([(x, y, z_road), (x, y, z_walk)])
for idx in range(len(rows) - 1):
i = idx * 2
faces.append((i, i + 2, i + 3, i + 1))
mesh = bpy.data.meshes.new(name)
mesh.from_pydata(verts, [], faces)
mesh.update()
mesh.materials.append(concrete)
obj = bpy.data.objects.new(name, mesh)
bpy.context.scene.collection.objects.link(obj)
return obj
kerb_faces(SOUTH_GUTTER, "Kerb_South")
kerb_faces(NORTH_GUTTER, "Kerb_North")
# Continental zebra markings: one band per signalised crossing. Bars run
# along the road (traffic direction), side by side across the carriageway;
# a pedestrian crosses perpendicular to them. Lifted 1 cm above the road
# surface (which is itself 2 cm above the DEM) to avoid z-fighting.
paint = bpy.data.materials.new("Road_Paint_White")
paint.diffuse_color = (0.85, 0.85, 0.85, 1.0)
def crossing_band(s_c):
zone = 3.0 # band length along the road, m
w, g = 0.5, 0.5 # stripe width / gap, m
span = (SOUTH_GUTTER + 0.2, NORTH_GUTTER - 0.2)
verts, faces = [], []
n = int(zone // (w + g))
for k in range(n):
s0 = s_c - zone / 2 + k * (w + g)
corners = []
for s_edge in (s0, s0 + w):
base, normal, _ = at(s_edge)
for off in span:
x = base[0] + off * normal[0]
y = base[1] + off * normal[1]
corners.append((len(verts), (x, y, (dem_z(x, y) or 0.0) + 0.03)))
# corners order: (s0,off_s), (s0,off_n), (s1,off_s), (s1,off_n)
idx = [c[0] for c in corners]
verts.extend(c[1] for c in corners)
faces.append((idx[0], idx[1], idx[3], idx[2]))
mesh = bpy.data.meshes.new("Crossing_Markings")
mesh.from_pydata(verts, [], faces)
mesh.update()
mesh.materials.append(paint)
obj = bpy.data.objects.new("Crossing_Markings", mesh)
bpy.context.scene.collection.objects.link(obj)
return obj
for s_c in CROSSINGS:
band = crossing_band(s_c)
print(f"crossing band at s={s_c:.1f}: {len(band.data.polygons)} stripes")
for obj in (road, sw_s, sw_n):
print(f"{obj.name:16} verts {len(obj.data.vertices):5} faces {len(obj.data.polygons):5}")
# crown check on the built mesh
mid = total / 2
for off in (SOUTH_GUTTER, -5.0, 0.0, 5.0, NORTH_GUTTER):
base, normal, _ = at(mid)
x = base[0] + off * normal[0]
y = base[1] + off * normal[1]
zr = road_z(0, off, x, y)
print(f" crown at {off:+5.1f} m: road Z {zr:+.2f} m")
out = os.path.abspath(args.out)
os.makedirs(os.path.dirname(out), exist_ok=True)
bpy.ops.wm.save_as_mainfile(filepath=out)
print(f"saved {out}")
if __name__ == "__main__":
main()