Mineflayer physics refactor (#2492)

* add tests that fail

* fixed a test

* fix: set velocity to 0 only if it is absolute

* refactor: precise physics timer & limiter

* refactor: position update logic

* fix: minor issues

* add: death ticking

chunk check was not working properly

* change packet object

* unhardcode deltaSeconds limiter

* add deprecated notice for physicTick

* add physics chunk check

* Karang changes

added back lastSent optimization
moved depercated event to bot.on('newListener'
removed tick limiter for now

* Karang changes part 2

* Karang changes part 3

* remove speedy setInterval

* remove 50ms test

* cache supportFeature check (thanks Ic3Tank)

* remove tests that rely on precise timing

* lint

* change console.log to warn
remove debug comment

* add configurable "maxCatchupTicks"
rename isDead to sendPositionPacketInDeath

Author: U5B

.gitignore

@@ -8,4 +8,5 @@ versions/
 server_jars/
 test/server_*
 .vscode
-.DS_Store
+.DS_Store
+launcher_accounts.json

lib/plugins/physics.js

@@ -12,9 +12,10 @@ module.exports = inject
 const PI = Math.PI
 const PI_2 = Math.PI * 2
 const PHYSICS_INTERVAL_MS = 50
-const PHYSICS_TIMESTEP = PHYSICS_INTERVAL_MS / 1000
+const PHYSICS_TIMESTEP = PHYSICS_INTERVAL_MS / 1000 // 0.05
 
-function inject (bot, { physicsEnabled }) {
+function inject (bot, { physicsEnabled, maxCatchupTicks }) {
+  const PHYSICS_CATCHUP_TICKS = maxCatchupTicks ?? 4
   const world = { getBlock: (pos) => { return bot.blockAt(pos, false) } }
   const physics = Physics(bot.registry, world)
 
@@ -38,6 +39,7 @@ function inject (bot, { physicsEnabled }) {
   let lastPhysicsFrameTime = null
   let shouldUsePhysics = false
   bot.physicsEnabled = physicsEnabled ?? true
+  let deadTicks = 21
 
   const lastSent = {
     x: 0,
@@ -51,25 +53,44 @@ function inject (bot, { physicsEnabled }) {
 
   // This function should be executed each tick (every 0.05 seconds)
   // How it works: https://gafferongames.com/post/fix_your_timestep/
+
+  // WARNING: THIS IS NOT ACCURATE ON WINDOWS (15.6 Timer Resolution)
+  // use WSL or switch to Linux
+  // see: https://discord.com/channels/413438066984747026/519952494768685086/901948718255833158
   let timeAccumulator = 0
+  let catchupTicks = 0
   function doPhysics () {
     const now = performance.now()
     const deltaSeconds = (now - lastPhysicsFrameTime) / 1000
     lastPhysicsFrameTime = now
 
     timeAccumulator += deltaSeconds
-
+    catchupTicks = 0
     while (timeAccumulator >= PHYSICS_TIMESTEP) {
-      if (bot.physicsEnabled && shouldUsePhysics) {
-        physics.simulatePlayer(new PlayerState(bot, controlState), world).apply(bot)
-        bot.emit('physicsTick')
-        bot.emit('physicTick') // Deprecated, only exists to support old plugins. May be removed in the future
-      }
-      updatePosition(PHYSICS_TIMESTEP)
+      tickPhysics(now)
       timeAccumulator -= PHYSICS_TIMESTEP
+      catchupTicks++
+      if (catchupTicks >= PHYSICS_CATCHUP_TICKS) break
+    }
+  }
+
+  function tickPhysics (now) {
+    if (bot.blockAt(bot.entity.position) == null) return // check if chunk is unloaded
+    if (bot.physicsEnabled && shouldUsePhysics) {
+      physics.simulatePlayer(new PlayerState(bot, controlState), world).apply(bot)
+      bot.emit('physicsTick')
+      bot.emit('physicTick') // Deprecated, only exists to support old plugins. May be removed in the future
+    }
+    if (shouldUsePhysics) {
+      updatePosition(now)
     }
   }
 
+  // remove this when 'physicTick' is removed
+  bot.on('newListener', (name) => {
+    if (name === 'physicTick') console.warn('Mineflayer detected that you are using a deprecated event (physicTick)! Please use this event (physicsTick) instead.')
+  })
+
   function cleanup () {
     clearInterval(doPhysicsTimer)
     doPhysicsTimer = null
@@ -117,17 +138,25 @@ function inject (bot, { physicsEnabled }) {
     return dYaw
   }
 
-  function updatePosition (dt) {
-    // If you're dead, you're probably on the ground though ...
-    if (!bot.isAlive) bot.entity.onGround = true
+  // returns false if packet should be sent, true if not
+  function sendPositionPacketInDeath () {
+    if (bot.isAlive === true) deadTicks = 0
+    if (bot.isAlive === false && deadTicks <= 20) deadTicks++
+    if (deadTicks >= 20) return true
+    return false
+  }
+
+  function updatePosition (now) {
+    // Only send updates for 20 ticks after death
+    if (sendPositionPacketInDeath()) return
 
     // Increment the yaw in baby steps so that notchian clients (not the server) can keep up.
     const dYaw = deltaYaw(bot.entity.yaw, lastSentYaw)
     const dPitch = bot.entity.pitch - (lastSentPitch || 0)
 
     // Vanilla doesn't clamp yaw, so we don't want to do it either
-    const maxDeltaYaw = dt * physics.yawSpeed
-    const maxDeltaPitch = dt * physics.pitchSpeed
+    const maxDeltaYaw = PHYSICS_TIMESTEP * physics.yawSpeed
+    const maxDeltaPitch = PHYSICS_TIMESTEP * physics.pitchSpeed
     lastSentYaw += math.clamp(-maxDeltaYaw, dYaw, maxDeltaYaw)
     lastSentPitch += math.clamp(-maxDeltaPitch, dPitch, maxDeltaPitch)
 
@@ -137,24 +166,28 @@ function inject (bot, { physicsEnabled }) {
     const onGround = bot.entity.onGround
 
     // Only send a position update if necessary, select the appropriate packet
-    const positionUpdated = lastSent.x !== position.x || lastSent.y !== position.y || lastSent.z !== position.z
+    const positionUpdated = lastSent.x !== position.x || lastSent.y !== position.y || lastSent.z !== position.z ||
+    // Send a position update every second, even if no other update was made
+    // This function rounds to the nearest 50ms (or PHYSICS_INTERVAL_MS) and checks if a second has passed.
+    (Math.round((now - lastSent.time) / PHYSICS_INTERVAL_MS) * PHYSICS_INTERVAL_MS) >= 1000
     const lookUpdated = lastSent.yaw !== yaw || lastSent.pitch !== pitch
 
-    if (positionUpdated && lookUpdated && bot.isAlive) {
+    if (positionUpdated && lookUpdated) {
       sendPacketPositionAndLook(position, yaw, pitch, onGround)
-    } else if (positionUpdated && bot.isAlive) {
+      lastSent.time = now // only reset if positionUpdated is true
+    } else if (positionUpdated) {
       sendPacketPosition(position, onGround)
-    } else if (lookUpdated && bot.isAlive) {
+      lastSent.time = now // only reset if positionUpdated is true
+    } else if (lookUpdated) {
       sendPacketLook(yaw, pitch, onGround)
-    } else if (performance.now() - lastSent.time >= 1000) {
-      // Send a position packet every second, even if no update was made
-      sendPacketPosition(position, onGround)
-      lastSent.time = performance.now()
-    } else if (positionUpdateSentEveryTick && bot.isAlive) {
+    } else if (positionUpdateSentEveryTick || onGround !== lastSent.onGround) {
       // For versions < 1.12, one player packet should be sent every tick
       // for the server to update health correctly
+      // For versions >= 1.12, onGround !== lastSent.onGround should be used, but it doesn't ever trigger outside of login
       bot._client.write('flying', { onGround: bot.entity.onGround })
     }
+
+    lastSent.onGround = bot.entity.onGround // onGround is always set
   }
 
   bot.physics = physics
@@ -262,7 +295,14 @@ function inject (bot, { physicsEnabled }) {
   // player position and look (clientbound)
   bot._client.on('position', (packet) => {
     bot.entity.height = 1.62
-    bot.entity.velocity.set(0, 0, 0)
+
+    // Velocity is only set to 0 if the flag is not set, otherwise keep current velocity
+    const vel = bot.entity.velocity
+    vel.set(
+      packet.flags & 1 ? vel.x : 0,
+      packet.flags & 2 ? vel.y : 0,
+      packet.flags & 4 ? vel.z : 0
+    )
 
     // If flag is set, then the corresponding value is relative, else it is absolute
     const pos = bot.entity.position
@@ -280,19 +320,14 @@ function inject (bot, { physicsEnabled }) {
 
     if (bot.supportFeature('teleportUsesOwnPacket')) {
       bot._client.write('teleport_confirm', { teleportId: packet.teleportId })
-      // Force send an extra packet to be like vanilla client
-      sendPacketPositionAndLook(pos, newYaw, newPitch, bot.entity.onGround)
     }
     sendPacketPositionAndLook(pos, newYaw, newPitch, bot.entity.onGround)
 
     shouldUsePhysics = true
-    bot.entity.timeSinceOnGround = 0
+    bot.jumpTicks = 0
     lastSentYaw = bot.entity.yaw
+    lastSentPitch = bot.entity.pitch
 
-    if (doPhysicsTimer === null) {
-      lastPhysicsFrameTime = performance.now()
-      doPhysicsTimer = setInterval(doPhysics, PHYSICS_INTERVAL_MS)
-    }
     bot.emit('forcedMove')
   })
 
@@ -313,5 +348,12 @@ function inject (bot, { physicsEnabled }) {
 
   bot.on('mount', () => { shouldUsePhysics = false })
   bot.on('respawn', () => { shouldUsePhysics = false })
+  bot.on('login', () => {
+    shouldUsePhysics = false
+    if (doPhysicsTimer === null) {
+      lastPhysicsFrameTime = performance.now()
+      doPhysicsTimer = setInterval(doPhysics, PHYSICS_INTERVAL_MS)
+    }
+  })
   bot.on('end', cleanup)
 }

test/internalTest.js

@@ -4,6 +4,7 @@ const mineflayer = require('../')
 const vec3 = require('vec3')
 const mc = require('minecraft-protocol')
 const assert = require('assert')
+const { sleep } = require('../lib/promise_utils')
 
 for (const supportedVersion of mineflayer.testedVersions) {
   const registry = require('prismarine-registry')(supportedVersion)
@@ -224,7 +225,147 @@ for (const supportedVersion of mineflayer.testedVersions) {
 
     describe('physics', () => {
       const pos = vec3(1, 65, 1)
+      const pos2 = vec3(2, 65, 1)
       const goldId = 41
+      it('no physics if there is no chunk', (done) => {
+        let fail = 0
+        const basePosition = {
+          x: 1.5,
+          y: 66,
+          z: 1.5,
+          pitch: 0,
+          yaw: 0,
+          flags: 0,
+          teleportId: 0
+        }
+        server.on('login', async (client) => {
+          await client.write('login', bot.test.generateLoginPacket())
+          await client.write('position', basePosition)
+          client.on('packet', (data, meta) => {
+            const packetName = meta.name
+            switch (packetName) {
+              case 'position':
+                fail++
+                break
+              case 'position_look':
+                fail++
+                break
+              case 'look':
+                fail++
+                break
+            }
+            if (fail > 1) assert.fail('position packet sent')
+          })
+          await sleep(2000)
+          done()
+        })
+      })
+      it('absolute position & relative position (velocity)', (done) => {
+        server.on('login', async (client) => {
+          await client.write('login', bot.test.generateLoginPacket())
+          const chunk = await bot.test.buildChunk()
+
+          await chunk.setBlockType(pos, goldId)
+          await chunk.setBlockType(pos2, goldId)
+          await client.write('map_chunk', generateChunkPacket(chunk))
+          let check = true
+          let absolute = true
+          const basePosition = {
+            x: 1.5,
+            y: 66,
+            z: 1.5,
+            pitch: 0,
+            yaw: 0,
+            flags: 0,
+            teleportId: 0
+          }
+          client.on('packet', (data, meta) => {
+            const packetName = meta.name
+            switch (packetName) {
+              case 'teleport_confirm': {
+                assert.ok(basePosition.teleportId === data.teleportId)
+                break
+              }
+              case 'position_look': {
+                if (!check) return
+                if (absolute) {
+                  assert.ok(bot.entity.velocity.y === 0)
+                } else {
+                  assert.ok(bot.entity.velocity.y !== 0)
+                }
+                assert.ok(basePosition.x === data.x)
+                assert.ok(basePosition.y === data.y)
+                assert.ok(basePosition.z === data.z)
+                assert.ok(basePosition.yaw === data.yaw)
+                assert.ok(basePosition.pitch === data.pitch)
+                check = false
+                break
+              }
+              default:
+                break
+            }
+          })
+          // Absolute Position Tests
+          // absolute position test
+          check = true
+          await client.write('position', basePosition)
+          await bot.waitForTicks(5)
+          // absolute position test 2
+          basePosition.x = 2.5
+          basePosition.teleportId = 1
+          await bot.waitForTicks(1)
+          check = true
+          await client.write('position', basePosition)
+          await bot.waitForTicks(2)
+          // absolute position test 3
+          basePosition.x = 1.5
+          basePosition.teleportId = 2
+          await bot.waitForTicks(1)
+          check = true
+          await client.write('position', basePosition)
+          await bot.waitForTicks(2)
+
+          // Relative Position Tests
+          const relativePosition = {
+            x: 1,
+            y: 0,
+            z: 0,
+            pitch: 0,
+            yaw: 0,
+            flags: 31,
+            teleportId: 3
+          }
+          absolute = false
+          // relative position test 1
+          basePosition.x = 2.5
+          basePosition.teleportId = 3
+          relativePosition.x = 1
+          relativePosition.teleportId = 3
+          await bot.waitForTicks(1)
+          check = true
+          await client.write('position', relativePosition)
+          await bot.waitForTicks(2)
+          // relative position test 2
+          basePosition.x = 1.5
+          basePosition.teleportId = 4
+          relativePosition.x = -1
+          relativePosition.teleportId = 4
+          await bot.waitForTicks(1)
+          check = true
+          await client.write('position', relativePosition)
+          await bot.waitForTicks(2)
+          // relative position test 3
+          basePosition.x = 2.5
+          basePosition.teleportId = 5
+          relativePosition.x = 1
+          relativePosition.teleportId = 5
+          await bot.waitForTicks(1)
+          check = true
+          await client.write('position', relativePosition)
+          await bot.waitForTicks(2)
+          done()
+        })
+      })
       it('gravity + land on solid block + jump', (done) => {
         let y = 80
         let landed = false