程序画布城市景观

下载代码

html

css

分享到微信朋友圈

html

css

JavaScript

console.clear()

// OVERENGINEERED UNOPTIMIZED CANVAS BULLSH*T
// BUT IT'S OKAY SINCE IT'S BLADE RUNNER INNIT

// Some stuff left unoptimized / verbose to show the work.

// TODO:
// - optimize render loop, avoid overdraws, etc
// - smoothly fade rows in on the horizon

// Constants.  Change at own risk
const CANVAS_WIDTH = 900
const CANVAS_HEIGHT = 300
const FRAME_TIME = 1000 / 16
const LIGHT_ROWS = 20
const LIGHT_ROW_DEPTH = 2
const LIGHT_SPACING = 0.6
const LIGHT_SIZE = 0.1
const LIGHT_SCATTER = 0.4
const BUILDING_ROWS = 38
const BUILDING_ROW_DEPTH = 1
const BUILDING_ROW_WIDTH = 60
const BUILDING_MIN_HEIGHT = 1.5
const BUILDING_MAX_HEIGHT = 3
const STACK_HEIGHT = 9
const STACK_THRESHOLD = 0.87
const STACK_LIGHT_CHANCE = 0.95
const STACK_LIGHT_SIZE = 0.13
const FADE_GRAY_VALUE = 25
const FADE_OFFSET = 0.35

// Virtual camera. Used in perspective calculations
const CAMERA = {
   x: 0,
   y: 10,
   z: 0,
   fov: 170,
   dist: 30,
   zSpeed: 0.005,
}

// Virtual vanishing point XY. Used in perspective calculations
const VP_OFS = {
   x: 0.5,
   y: 0.27,
}

// Global hoisted vars for rendering contexts and timers
let c, ctx, output_c, output_ctx
let _t, _dt, _ft

// Seedable random number generator.
// Not particularly well-distributed, but fine for this case.
// Allows us to emit the same set of random numbers on every frame
// so we can consistently re-render the scene.
const RNG = {
   seed: 1,
   random() {
      const x = Math.sin(RNG.seed++) * 10000
      return x - (x << 0)
   },
   randomInRange(min, max) {
      return ((RNG.random() * (max - min + 1)) << 0) + min
   }
}

// Module to get a random colour from a predefined list.
// Uses the seedable RNG
const Palette = (() => {
   const PAL = ['black', '#111', '#113', 'white', 'sliver', '#f88', 'orange', 'oldlace', '#569']
   const lastIndex = PAL.length - 1

function getRandomFromPalette() {
      return PAL[RNG.randomInRange(0, lastIndex)]
   }

return {
      getRandom: getRandomFromPalette
   }
})()

function ceil(n) {
   var f = (n << 0), f = f == n ? f : f + 1
   return f
}

// Update method of main loop
function update() {
   // Update our global timestamp (used in rendering)
   _t = Date.now() * 0.001
      // Move the camera slowly 'forward'
   CAMERA.z += CAMERA.zSpeed
}

// Draw a frame of the scene.
// Uses the current timestamp and the seeded RNG to render a
// pseudorandom cityscape with lights and buildings.
// We always generate and draw a set amount of city in front of
// the camera, so it appears to be endless as we 'fly over' it.
//
// 1. Clear the whole scene
// 2. Render random rows of lights
// 3. Render random rows of buildings
// 4. Blit scene to onscreen canvas
let _$ = {
   vPointX: 0,
   vPointY: 0,
   rowScreenX: 0,
   MAX_LIGHTS: 0,
   closestLightRow: 0,
   rowZ: 0,
   rowRelativeZ: 0,
   scalingFactor: 0,
   rowScreenWidth: 0,
   rowScreenHeight: 0,
   rowScreenY: 0,
   rowScreenLightSpacing: 0,
   rowLightCount: 0,
   lightSize: 0,
   lightHalfSize: 0,
   lightScreenX: 0,
   lightScreenY: 0,
   closestBuildingRow: 0,
   rowBuildingCount: 0,
   rowBuildingScreenWidth: 0,
   rowShade: 0,
   rowStyleString: '',
   lightData: [],
   isStack: false,
   buildingHeight: 0,
   buildingScreenHeight: 0,
   buildingScreenX: 0,
   buildingScreenY: 0,
   lightSize: 0,
   lightHalfSize: 0,
   lightColor: 0,
}
function render() {

// Calculate the pixel XY of the vanishing point
   // (could be done on init, but useful if we ever want to
   // dynamically move the camera)
   _$.vPointX = c.width * VP_OFS.x >> 0
   _$.vPointY = c.height * VP_OFS.y >> 0

// If we wanted to, we could give each row an X offset
   // and include it in perspective calculations,
   // but we just use the centre alignment for each one here.
   _$.rowScreenX = CAMERA.x + _$.vPointX

// 1. Clear the whole scene...
   // (canvases are transparent so that the CSS 'sky' gradient can be seen)
   ctx.clearRect(0, 0, c.width, c.height)
   output_ctx.clearRect(0, 0, output_c.width, output_c.height)

// 2. Render random rows of lights...

// Calculate the closest row to the camera so we
   // can render the required number of rows into the distance
   _$.closestLightRow = Math.floor(CAMERA.z / LIGHT_ROW_DEPTH)

// Draw each row of lights
   for (let i = 0; i < LIGHT_ROWS; i++) {

// Calculate this row's base Z position
      // and Z relative to camera
      _$.rowZ = (_$.closestLightRow * LIGHT_ROW_DEPTH) + (LIGHT_ROW_DEPTH * i)
      _$.rowRelativeZ = _$.rowZ - CAMERA.z

// Don't draw the row if it's behind the camera,
      // or beyond the camera's draw distance
      if (_$.rowRelativeZ <= 0 || _$.rowRelativeZ > CAMERA.dist) {
         continue
      }

// Get the perspective scaling factor and pixel Y position for this row
      _$.scalingFactor = CAMERA.fov / _$.rowRelativeZ
      _$.rowScreenY = CAMERA.y * _$.scalingFactor + _$.vPointY

// Don't draw the row if it's off-canvas
      if (_$.rowScreenY > c.height) {
         continue
      }

// Calculate the spacing and number of lights we need to render for this row
      _$.rowScreenLightSpacing = LIGHT_SPACING * _$.scalingFactor
      _$.rowLightCount = c.width / _$.rowScreenLightSpacing

// Seed the RNG in a way that gets us decent distribution 
      // for the random lights
      RNG.seed = _$.rowZ * 0.573

// Render the random lights for this row
      for (let j = 0; j < _$.rowLightCount; j++) {

// Randomize light size, with perspective
         _$.lightSize = RNG.random() * (LIGHT_SIZE * _$.scalingFactor)
         _$.lightHalfSize = _$.lightSize * 0.5

// Randomly offset the XY of the light, with perspective
         _$.lightScreenX = (j * _$.rowScreenLightSpacing) +
            (RNG.random() * LIGHT_SCATTER * _$.scalingFactor) - _$.lightHalfSize
         _$.lightScreenY = (_$.rowScreenY + (RNG.random() * LIGHT_SCATTER) * _$.scalingFactor) - _$.lightHalfSize

// Don't render if the light is offscreen
         if (_$.lightScreenX < 0 || _$.lightScreenX > c.width ||
            _$.lightScreenY > c.height) {
            // HACK: we still need to call the RNG the same number of times 
            // for every row to ensure consistency between frames. If we didn't
            // do this, the lights would jump all over the place near the edges
            // of the screen.
            Palette.getRandom()
            continue
         }

// Pick a random colour for this light
         ctx.fillStyle = Palette.getRandom()

// Render the light twice, mirrored either side of the centre vanishing point.
         // Saves us having to do perspective offset calculation for every light,
         // and won't be noitceable when we overlay the city buildings.
         ctx.fillRect((_$.rowScreenX + _$.lightScreenX), 
                      _$.lightScreenY, _$.lightSize, _$.lightSize)
         ctx.fillRect((_$.rowScreenX - _$.lightScreenX), 
                      _$.lightScreenY, _$.lightSize, _$.lightSize)
      }
   }

// 3. Render random rows of buildings...

// Calculate the closest row to the camera so we
   // can render the required number of rows into the distance
   _$.closestBuildingRow = Math.floor(CAMERA.z / BUILDING_ROW_DEPTH)

// Draw each row of buildings
   for (let i = BUILDING_ROWS; i > 0; i--) {

// Calculate this row's base Z position
      // and Z relative to camera
      _$.rowZ = (_$.closestBuildingRow * BUILDING_ROW_DEPTH) + (BUILDING_ROW_DEPTH * i)
      _$.rowRelativeZ = _$.rowZ - CAMERA.z

// Don't draw the row if it's behind the camera,
      // or beyond the camera's draw distance
      if (_$.rowRelativeZ <= 0 || _$.rowRelativeZ > CAMERA.dist) {
         continue
      }

// Get the perspective scaling factor and pixel Y position for this row
      _$.scalingFactor = CAMERA.fov / _$.rowRelativeZ

// Calculate the perspective-scaled position and base size of our row.
      // Offset the XY so that the row's 'origin' is at centre bottom (i.e. ground-up)
      _$.rowScreenWidth = BUILDING_ROW_WIDTH * _$.scalingFactor;
      _$.rowScreenHeight = BUILDING_MAX_HEIGHT * _$.scalingFactor;
      _$.rowScreenX = CAMERA.x * _$.scalingFactor + _$.vPointX - (_$.rowScreenWidth * 0.5)
      _$.rowScreenY = CAMERA.y * _$.scalingFactor + _$.vPointY - _$.rowScreenHeight

// Seed the RNG to keep rendering consistent for this row
      RNG.seed = _$.rowZ

// Calculate a random number of buildings for this row
      // and get their screen width
      _$.rowBuildingCount = RNG.randomInRange(20, 70)
      _$.rowBuildingScreenWidth = _$.rowScreenWidth / _$.rowBuildingCount
      
      // Calculate the shade we want the buildings in this row to be.
      // The tint is darker nearer the camera, giving a sort of crude distance fog
      // near the horizon.
      _$.rowShade = Math.round(FADE_GRAY_VALUE * (_$.rowRelativeZ / (CAMERA.dist) - FADE_OFFSET))
      _$.rowStyleString = 'rgb(' + _$.rowShade + ',' + _$.rowShade + ',' + _$.rowShade + ')'

// Calclate and render each building
      _$.lightData.length = 0
      ctx.fillStyle = _$.rowStyleString
      for (let j = 0; j < _$.rowBuildingCount; j++) {

// Buildings have a certain chance to become a 'stack' i.e. way taller than 
         // everything else. We calculate a random ranged height for the building, 
         // and if it exceeds a threshold, it gets turned into a stack.
         _$.isStack = false
         _$.buildingHeight = Math.max(BUILDING_MIN_HEIGHT, RNG.random() * BUILDING_MAX_HEIGHT)

if (_$.buildingHeight > (BUILDING_MAX_HEIGHT * STACK_THRESHOLD)) {
            _$.isStack = true
            // Stacks have 40% height variance
            _$.buildingHeight = (STACK_HEIGHT * 0.6 + (RNG.random() * 0.4))
         }

// Calculate the pixel size and position of this building, adjusted for perspective
         _$.buildingScreenHeight = _$.buildingHeight * _$.scalingFactor
         _$.buildingScreenX = _$.rowScreenX + (j * _$.rowBuildingScreenWidth)
         _$.buildingScreenY = _$.rowScreenY + _$.rowScreenHeight - _$.buildingScreenHeight

// Draw the building on screen
         ctx.fillRect(_$.buildingScreenX, _$.buildingScreenY, Math.ceil(_$.rowBuildingScreenWidth), _$.buildingScreenHeight)

// Seed the RNG for consistency when calculating stack lights (if needed)
         RNG.seed = _$.buildingHeight + j

// Stacks have a chance to get lights on their top corners.
         // Generate and store light data so we can render it on top of the buildings
         if (_$.isStack && RNG.random() < STACK_LIGHT_CHANCE) {
            // Get random light size and color.
            // Slightly higher chance of red vs white lights
            _$.lightSize = RNG.random() * (STACK_LIGHT_SIZE * _$.scalingFactor)
            _$.lightColor = (RNG.random() > 0.6) ? 'white' : 'red'
            // Save light info for rendering after we do all the buildings
            // (helps minimixe changes to ctx.fillStyle)
            _$.lightData.push(_$.buildingScreenX)
            _$.lightData.push(_$.buildingScreenY)
            _$.lightData.push(_$.lightSize)
            _$.lightData.push(_$.lightColor)
         }
      }
      
      // Draw any lights on stacks that need them in this row
      for (let j = 0; j < _$.lightData.length; j += 4) {
         _$.buildingScreenX = _$.lightData[j]
         _$.buildingScreenY = _$.lightData[j+1]
         _$.lightSize = _$.lightData[j+2]
         _$.lightHalfSize = _$.lightSize * 0.5
         _$.lightColor = _$.lightData[j+3]
         
         // Draw lights centred at the top left and right corners of the stack
         ctx.fillStyle = _$.lightColor
         ctx.fillRect(_$.buildingScreenX - _$.lightHalfSize,
               _$.buildingScreenY - _$.lightHalfSize, _$.lightSize, _$.lightSize)
         ctx.fillRect(_$.buildingScreenX + _$.rowBuildingScreenWidth - _$.lightHalfSize,
               _$.buildingScreenY - _$.lightHalfSize, _$.lightSize, _$.lightSize)
      }
   }

// 4. Blit scene to onscreen canvas.
   // Now that we've built up the scene in-memory, we just render the image to
   // our canvas in the DOM.
   output_ctx.drawImage(c, 0, 0)
}

// Main loop.
// Maintains a consistent update rate, but draws the screen as often 
// as the browser will allow.
function frame() {
   requestAnimationFrame(frame)
   _ft = Date.now()
   update()
   if (_ft - _dt > FRAME_TIME) {
      render()
      _dt = _ft
   }
  
}

// Let's go!
function start() {
   // Init frame timers (see frame())
   _dt = _ft = Date.now()

// Create two canvases - one for in-memory compositing,
   // and another to go in the DOM for our final render.
   // Make them the same size as each other.
   c = document.createElement('canvas')
   ctx = c.getContext('2d')

output_c = document.createElement('canvas')
   output_ctx = output_c.getContext('2d')

output_c.width = c.width = CANVAS_WIDTH
   output_c.height = c.height = CANVAS_HEIGHT
   document.body.appendChild(output_c)

// Start the main loop.
   frame()
}

start()

粒子时间文字 hover canvas 3d 游戏音乐火焰水波轮播图鼠标跟随动画 css 加载动画导航菜单按钮滑块 tab 弹出层统计图 svg