# City Drive

A city in a landscape. A seeded city of Kenney's kits stands on ground
flattened for it, with traffic, street lights, and lit windows at night. Round
it are hills, woods and a sea under the whole sky: sun and moon, a cloud deck,
the stars. Drive out of town and keep going.

## Demo

```js
import {
  b3d, b3dSun, b3dSkybox, b3dLight, b3dFog, b3dTerrain, b3dCloudDeck, b3dDecorator, b3dWater,
  b3dCity, b3dCar, b3dLibrary, inputFocus, cityGround, cityStart, slider3d, assetUrl,
  effectiveTier, headsetDevice,
} from 'tosijs-3d'
import { tosi } from 'tosijs'

const { cityDrive } = tosi({ cityDrive: { time: 17.5, speed: 60, coverage: 0.45 } })

// A LIGHTER WORLD on a headset or a low-powered device: a smaller town, less
// traffic, a shorter view, fewer trees, no cloud deck. A headset draws
// everything twice, and its browser pays dearly for every draw.
const light = headsetDevice() || effectiveTier() === 'low'

// The city's plan, and where it stands: its ground is flattened at `level`
// under the whole grid and eased back into the hills round it.
const plan = light ? { width: 24, depth: 24, seed: 3 } : { width: 48, depth: 48, seed: 3 }
const level = 12
const ground = cityGround({ ...plan, level })
const start = cityStart(plan)

const terrain = b3dTerrain({
  seed: 7,
  biome: 'on',
  surfaceType: 'cylinder',
  radius: 1000,
  cylinderHeight: 1000,
  tileSize: 128,
  lodLevels: light ? 2 : 3,
  splitFactor: 2,
  reach: light ? 1500 : 4000,
  grossScale: 0.015,
  detailScale: 0.09,
  horizScale: 8,
  grossAmplitude: 160,
  detailAmplitude: 10,
  // Down, so the low ground is under the sea at 0.
  baseHeight: -70,
  // Green country: moist, and cooling slowly enough with height that the
  // hills are not snow-capped.
  biomeMoisture: 0.9,
  biomeLapseRate: 0.0015,
})
terrain.landform = ground.landform
terrain.regenerate()

const woods = b3dDecorator(light ? { budget: 1200, radius: 400 } : { budget: 5000, radius: 900 })
woods.clear = ground.clear

preview.append(
  b3d(
    {
      style: 'width: 100%; height: 100%',
      gamepad: 'left_stick,right_stick,left_trigger,right_trigger,right_bumper,A,X',
      panelTitle: 'City Drive',
      scenePanel: () => [
        slider3d({ label: 'time of day', value: cityDrive.time, min: 0, max: 24, step: 0.1 }),
        slider3d({ label: 'time speed', value: cityDrive.speed, min: 0, max: 600, step: 10 }),
        ...(light ? [] : [slider3d({ label: 'cloud cover', value: cityDrive.coverage, min: 0, max: 1.5, step: 0.05 })]),
      ],
    },
    b3dSun({ shadowTextureSize: 2048 }),
    b3dSkybox({
      timeOfDay: cityDrive.time,
      realtimeScale: cityDrive.speed,
      starfieldCube: '/sky/nebula',
      starfieldData: '/sky/stars',
      starfieldTilt: '12,25,58',
    }),
    b3dLight({ intensity: 0.5, nightIntensity: 0.06, groundColor: '#4b4d52' }),
    b3dFog({ syncSkybox: true, start: light ? 400 : 800, end: light ? 1400 : 3500 }),
    terrain,
    woods,
    ...(light ? [] : [b3dCloudDeck({ altitude: 600, coverage: cityDrive.coverage, orographic: 0.6, wind: 8 })]),
    b3dWater({ y: 0, waterSize: 8000, follow: true, twoSided: true }),
    b3dLibrary({ url: assetUrl('kenney/libraries/car-kit.glb'), type: 'cars' }),
    b3dCity({ ...plan, y: level, traffic: light ? 12 : 32 }),
    inputFocus(
      b3dCar({ library: 'cars', meshName: 'sedan-sports', scale: 1.7, player: true, ...start, y: level + 0.5 })
    )
  )
)
```
```css
.preview { height: 100%; }
```

On a headset or a low-powered device the world is lighter: a town a quarter
the size, a dozen cars, a shorter view, fewer trees and no cloud deck.

You start in the middle of town. The right trigger or **W** drives, the left
trigger, the right bumper or **S** brakes and reverses, and the left stick or
**A** and **D** steer. The right stick or the arrow keys swing the camera round
the car (it springs back behind) and up an arc toward overhead (it stays
there). Time runs
at 60×, so the sun goes down soon after you arrive. The owl's panel sets the
hour, the speed and the cloud.

## How it is put together

- [b3d-city](/b3d-city/) builds the town. `cityGround` gives the terrain a
  [landform](/landform/) pad, flat under the grid, and gives the woods a
  `clear` that keeps trees off the streets. `cityStart` is a clear spot in
  the middle to start the car.
- [b3d-terrain](/b3d-terrain/) and [b3d-decorator](/b3d-decorator/) make the
  country, [b3d-cloud-deck](/b3d-cloud-deck/) the weather, and
  [b3d-skybox](/b3d-skybox/) the day and night.
- The traffic ([city-traffic](/city-traffic/)) stays on the town's roads.
  Your car goes anywhere there is ground.