From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Thu, 2 Jul 2020 12:02:43 -0700
Subject: [PATCH] Optimise collision checking in player move packet handling

Move collision logic to just the hasNewCollision call instead of getCubes + hasNewCollision

CHECK ME

diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 4a1fe620ab2a6efadf734c1d7b09784e3865291c..5a99ca1121ef2163b194372c48bf03e95a96b8ea 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -572,7 +572,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                     return;
                 }
 
-                boolean flag = worldserver.noCollision(entity, entity.getBoundingBox().deflate(0.0625D));
+                AABB oldBox = entity.getBoundingBox(); // Paper - copy from player movement packet
 
                 d6 = d3 - this.vehicleLastGoodX; // Paper - diff on change, used for checking large move vectors above
                 d7 = d4 - this.vehicleLastGoodY - 1.0E-6D; // Paper - diff on change, used for checking large move vectors above
@@ -588,6 +588,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 }
 
                 entity.move(MoverType.PLAYER, new Vec3(d6, d7, d8));
+                boolean didCollide = toX != entity.getX() || toY != entity.getY() || toZ != entity.getZ(); // Paper - needed here as the difference in Y can be reset - also note: this is only a guess at whether collisions took place, floating point errors can make this true when it shouldn't be...
                 double d11 = d7;
 
                 d6 = d3 - entity.getX();
@@ -601,15 +602,23 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 boolean flag2 = false;
 
                 if (d10 > org.spigotmc.SpigotConfig.movedWronglyThreshold) { // Spigot
-                    flag2 = true;
+                    flag2 = true; // Paper - diff on change, this should be moved wrongly
                     ServerGamePacketListenerImpl.LOGGER.warn("{} (vehicle of {}) moved wrongly! {}", new Object[]{entity.getName().getString(), this.player.getName().getString(), Math.sqrt(d10)});
                 }
 
                 entity.absMoveTo(d3, d4, d5, f, f1);
                 this.player.absMoveTo(d3, d4, d5, this.player.getYRot(), this.player.getXRot()); // CraftBukkit
-                boolean flag3 = worldserver.noCollision(entity, entity.getBoundingBox().deflate(0.0625D));
 
-                if (flag && (flag2 || !flag3)) {
+                // Paper start - optimise out extra getCubes
+                boolean teleportBack = flag2; // violating this is always a fail
+                if (!teleportBack) {
+                    // note: only call after setLocation, or else getBoundingBox is wrong
+                    AABB newBox = entity.getBoundingBox();
+                    if (didCollide || !oldBox.equals(newBox)) {
+                        teleportBack = this.hasNewCollision(worldserver, entity, oldBox, newBox);
+                    } // else: no collision at all detected, why do we care?
+                }
+                if (teleportBack) { // Paper end - optimise out extra getCubes
                     entity.absMoveTo(d0, d1, d2, f, f1);
                     this.player.absMoveTo(d0, d1, d2, this.player.getYRot(), this.player.getXRot()); // CraftBukkit
                     this.send(new ClientboundMoveVehiclePacket(entity));
@@ -688,7 +697,32 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     }
 
     private boolean noBlocksAround(Entity entity) {
-        return entity.level().getBlockStates(entity.getBoundingBox().inflate(0.0625D).expandTowards(0.0D, -0.55D, 0.0D)).allMatch(BlockBehaviour.BlockStateBase::isAir);
+        // Paper start - stop using streams, this is already a known fixed problem in Entity#move
+        AABB box = entity.getBoundingBox().inflate(0.0625D).expandTowards(0.0D, -0.55D, 0.0D);
+        int minX = Mth.floor(box.minX);
+        int minY = Mth.floor(box.minY);
+        int minZ = Mth.floor(box.minZ);
+        int maxX = Mth.floor(box.maxX);
+        int maxY = Mth.floor(box.maxY);
+        int maxZ = Mth.floor(box.maxZ);
+
+        Level world = entity.level();
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+
+        for (int y = minY; y <= maxY; ++y) {
+            for (int z = minZ; z <= maxZ; ++z) {
+                for (int x = minX; x <= maxX; ++x) {
+                    pos.set(x, y, z);
+                    BlockState type = world.getBlockStateIfLoaded(pos);
+                    if (type != null && !type.isAir()) {
+                        return false;
+                    }
+                }
+            }
+        }
+
+        return true;
+        // Paper end - stop using streams, this is already a known fixed problem in Entity#move
     }
 
     @Override
@@ -1283,7 +1317,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 }
 
                 if (this.awaitingPositionFromClient != null) {
-                    if (this.tickCount - this.awaitingTeleportTime > 20) {
+                    if (false && this.tickCount - this.awaitingTeleportTime > 20) { // Paper - this will greatly screw with clients with > 1000ms RTT
                         this.awaitingTeleportTime = this.tickCount;
                         this.teleport(this.awaitingPositionFromClient.x, this.awaitingPositionFromClient.y, this.awaitingPositionFromClient.z, this.player.getYRot(), this.player.getXRot());
                     }
@@ -1392,7 +1426,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                                 }
                             }
 
-                            AABB axisalignedbb = this.player.getBoundingBox();
+                            AABB axisalignedbb = this.player.getBoundingBox(); // Paper - diff on change, should be old AABB
 
                             d6 = d0 - this.lastGoodX; // Paper - diff on change, used for checking large move vectors above
                             d7 = d1 - this.lastGoodY; // Paper - diff on change, used for checking large move vectors above
@@ -1434,6 +1468,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
                             this.player.move(MoverType.PLAYER, new Vec3(d6, d7, d8));
                             this.player.onGround = packet.isOnGround(); // CraftBukkit - SPIGOT-5810, SPIGOT-5835, SPIGOT-6828: reset by this.player.move
+                            boolean didCollide = toX != this.player.getX() || toY != this.player.getY() || toZ != this.player.getZ(); // Paper - needed here as the difference in Y can be reset - also note: this is only a guess at whether collisions took place, floating point errors can make this true when it shouldn't be...
                             // Paper start - prevent position desync
                             if (this.awaitingPositionFromClient != null) {
                                 return; // ... thanks Mojang for letting move calls teleport across dimensions.
@@ -1464,7 +1499,17 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                             }
 
                             // Paper start - Add fail move event
-                            boolean teleportBack = !this.player.noPhysics && !this.player.isSleeping() && (movedWrongly && worldserver.noCollision(this.player, axisalignedbb) || this.isPlayerCollidingWithAnythingNew(worldserver, axisalignedbb, d0, d1, d2));
+                            // Paper start - optimise out extra getCubes
+                            boolean teleportBack = !this.player.noPhysics && !this.player.isSleeping() && movedWrongly;
+                            this.player.absMoveTo(d0, d1, d2, f, f1); // prevent desync by tping to the set position, dropped for unknown reasons by mojang
+                            if (!this.player.noPhysics && !this.player.isSleeping() && !teleportBack) {
+                                AABB newBox = this.player.getBoundingBox();
+                                if (didCollide || !axisalignedbb.equals(newBox)) {
+                                    // note: only call after setLocation, or else getBoundingBox is wrong
+                                    teleportBack = this.hasNewCollision(worldserver, this.player, axisalignedbb, newBox);
+                                } // else: no collision at all detected, why do we care?
+                            }
+                            // Paper end - optimise out extra getCubes
                             if (teleportBack) {
                                 io.papermc.paper.event.player.PlayerFailMoveEvent event = fireFailMove(io.papermc.paper.event.player.PlayerFailMoveEvent.FailReason.CLIPPED_INTO_BLOCK,
                                     toX, toY, toZ, toYaw, toPitch, false);
@@ -1570,6 +1615,33 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         }
     }
 
+    // Paper start - optimise out extra getCubes
+    private boolean hasNewCollision(final ServerLevel world, final Entity entity, final AABB oldBox, final AABB newBox) {
+        final List<AABB> collisionsBB = new java.util.ArrayList<>();
+        final List<VoxelShape> collisionsVoxel = new java.util.ArrayList<>();
+        io.papermc.paper.util.CollisionUtil.getCollisions(
+            world, entity, newBox, collisionsVoxel, collisionsBB,
+            io.papermc.paper.util.CollisionUtil.COLLISION_FLAG_COLLIDE_WITH_UNLOADED_CHUNKS | io.papermc.paper.util.CollisionUtil.COLLISION_FLAG_CHECK_BORDER,
+            null, null
+        );
+
+        for (int i = 0, len = collisionsBB.size(); i < len; ++i) {
+            final AABB box = collisionsBB.get(i);
+            if (!io.papermc.paper.util.CollisionUtil.voxelShapeIntersect(box, oldBox)) {
+                return true;
+            }
+        }
+
+        for (int i = 0, len = collisionsVoxel.size(); i < len; ++i) {
+            final VoxelShape voxel = collisionsVoxel.get(i);
+            if (!io.papermc.paper.util.CollisionUtil.voxelShapeIntersectNoEmpty(voxel, oldBox)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+    // Paper end - optimise out extra getCubes
     private boolean isPlayerCollidingWithAnythingNew(LevelReader world, AABB box, double newX, double newY, double newZ) {
         AABB axisalignedbb1 = this.player.getBoundingBox().move(newX - this.player.getX(), newY - this.player.getY(), newZ - this.player.getZ());
         Iterable<VoxelShape> iterable = world.getCollisions(this.player, axisalignedbb1.deflate(9.999999747378752E-6D));
