for i, j in ti.ndrange(8, 8): scene.set_voxel(ivec3(i, -8, j), 0, vec3(0))

start, end = 1+int(vec2(ti.random(),ti.random())*(ngrid-2)), 1+int(vec2(ti.random(),ti.random())*(ngrid-2))

turn = start + 1

while any((abs(turn-start)==1)|(abs(turn-end)==1)): turn = 1+int(vec2(ti.random(),ti.random())*(ngrid-2))

for k in ti.static([0, 1]):

d = vec2(k, 1-k); p = start[k]*vec2(1-k, k)-d

while p[1-k] < ngrid - 1:

p += d; scene.set_voxel(ivec3(p.x, -8, p.y), 1, vec3(0.5))

if p[1-k] == turn[1-k]: d = (1 if start[k] < end[k] else -1) * vec2(1-k, k)

if d.sum() <= 2:

if ((d.x | d.z) ^ (d.y | d.w)) & 1: uv = vec2(uv.y, uv.x) if (d.y | d.w) & 1 else uv

else: # curve

while d.z == 0 or d.w == 0: d = d.yzwx; uv=vec2(14-uv.y, uv.x)

uv = vec2(uv.norm(), ti.atan2(uv.x, uv.y)*2/pi*lgrid)

elif d.sum() >= 3: # junction

while d.sum() == 3 and d.y != 0: d = d.yzwx; uv=vec2(14-uv.y, uv.x) # rotate T-junction

if d.sum() > 3 or uv.x <= 7:

uv = vec2(mix(14-uv.x, uv.x, uv.x <= 7), mix(14-uv.y, uv.y, uv.y <= 7))

uv = vec2(uv.norm(), ti.atan2(uv.x, uv.y)*2/pi*lgrid)

scene.set_voxel(vec3(X.x, 0, X.y), 10, vec3(1 if uv.x==7 and 4<uv.y<12 else 0.5)) # pavement

if uv.x <= 1 or uv.x >= 13: scene.set_voxel(ivec3(X.x, 1, X.y), 11, vec3(0.7, 0.65, 0.6)) # sidewalk

if uv.y == 7 and (uv.x == 1 or uv.x == 13): # lights

for i in range(2, 9): scene.set_voxel(vec3(X.x, i, X.y), 50, vec3(0.6, 0.6, 0.6))

if uv.y == 7 and (1<=uv.x<=2 or 12<=uv.x<=13): scene.set_voxel(vec3(X.x, 8, X.y), 50, vec3(0.6, 0.6, 0.6))

while d.sum() > 0 and d.z == 0: d = d.yzwx; uv=vec2(14-uv.y, uv.x) # rotate

fl = int(3 + 10 * r); style = rand(r, 5)

wall = vec3(rand(r, 1),rand(r, 2),rand(r, 2)) * 0.2+0.4

wall2 = mix(vec3(rand(r, 9)*0.2+0.2), wall, style > 0.5 and rand(r, 4) < 0.4)

maxdist = ti.max(abs(uv.x - 7), abs(uv.y - 7))

for i in range(2, fl * 4):

light = mix(vec3(0.25,0.35,0.38), vec3(0.7,0.7,0.6), rand(rand(X.x, X.y), i//2)>0.6)

if maxdist < 6:

scene.set_voxel(vec3(X.x, i, X.y), mix(10, 0, i%4<2), mix(wall2, light, i%4<2))

if (uv.x == 2 or uv.x == 12) and (uv.y == 2 or uv.y == 12) or style>0.5 and (uv.x%3==1 or uv.y%3==1):

scene.set_voxel(vec3(X.x, i, X.y), 10, wall)

if maxdist < 5: scene.set_voxel(vec3(X.x, i, X.y), mix(10, 2, i%4<2), mix(wall, light, i%4<2))

if maxdist == 5:

for i in range(fl*4, fl*4+2): scene.set_voxel(vec3(X.x, i, X.y), 11, wall) # roof

if maxdist < 5: scene.set_voxel(vec3(X.x, fl*4, X.y), 11, vec3(rand(r, 7)*0.2+0.4))

for i in range(2): scene.set_voxel(vec3(X.x, i, X.y), 10, vec3(0.7, 0.65, 0.6)) # sidewalk

if fl > 10 and uv.x == 6 and uv.y == 6: # antenna

for i in range(fl+1):

scene.set_voxel(vec3(X.x, fl*5-i, X.y), mix(50, 2, i==0), mix(vec3(0.6), vec3(0.8,0,0), i==0))

if d.sum() > 0 and uv.y == 2 and 4 < uv.x < 10: # billboard

for i in range(5, 7):

scene.set_voxel(vec3(X.x,i,X.y), 2, vec3(int(r*3)==0,int(r*3)==1,int(r*3)==2)*(0.2+ti.random()*0.3))

for i in range(2, 5): scene.set_voxel(vec3(X.x,i,X.y), 0, vec3(0))

if d.sum() > 0 and uv.y == 3 and 4 < uv.x < 10:

for i in range(2, 5): scene.set_voxel(vec3(X.x,i,X.y), 1, vec3(0.7,0.7,0.6))

if ti.max(abs(uv.x - rand(r, 8)*7-4), abs(uv.y - rand(r, 10)*7-4)) < 1.5: # HVAC

center, height = int(vec2(rand(r, 1) * 7 + 4, rand(r, 2) * 7 + 4)), 9 + int(rand(r, 3)) * 5

for i in range(height + 3): # tree

if (uv - center).norm() < 1:

scene.set_voxel(vec3(X.x, i, X.y), 30, vec3(0.36, 0.18, 0.06))

if i > ti.min(height-4, (height+5)//2) and (uv - center).norm() < (height+3-i) * (rand(r, 4)*0.6 + 0.4):

scene.set_voxel(vec3(X.x, i, X.y), 80 if ti.random()<0.8 else 0, vec3(0.1, 0.3 + ti.random()*0.2, 0.1))

h = 2 * ti.sin((uv.x**2+uv.y**2+rand(r, 0)**2*256)/1024 * 2*pi) + 2 + (ti.random() > 0.95)

for i in range(int(h)): # grass

scene.set_voxel(vec3(X.x, i, X.y), 80, vec3(0.2, 0.5 + ti.random() * 0.2, 0.05))

if ti.max(abs(uv.x - rand(r, 4)*7-4), abs(uv.y - rand(r, 5)*7-4)) < 0.5: # light

for i in range(3):

for X in ti.grouped(ti.ndrange((-60, 60), (-60, 60))):

I, uv = (X+60) // lgrid, float((X + 60) % lgrid)

d = int(vec4(is_road(I.x,I.y+1),is_road(I.x+1,I.y),is_road(I.x,I.y-1),is_road(I.x-1,I.y)))

r = mix(rand(I.x, I.y), any(d>0), 0.4)

if is_road(I.x, I.y): build_road(X, uv, d)

elif r > 0.5: build_building(X, uv, d, 2*r-1)