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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Brokkonaut <hannos17@gmx.de>
Date: Sat, 18 Dec 2021 19:43:36 +0100
Subject: [PATCH] Workaround for client lag spikes (MC-162253)
When crossing certain chunk boundaries, the client needlessly
calculates light maps for chunk neighbours. In some specific map
configurations, these calculations cause a 500ms+ freeze on the Client.
This patch basically serves as a workaround by sending light maps
to the client, so that it doesn't attempt to calculate them.
This mitigates the frametime impact to a minimum (but it's still there).
Original patch by: MeFisto94 <MeFisto94@users.noreply.github.com>
Co-authored-by: =?UTF-8?q?Dani=C3=ABl=20Goossens?= <daniel@goossens.ch>
Co-authored-by: Nassim Jahnke <nassim@njahnke.dev>
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 77c89376495d90d0e7cbf6cd02c9a1c8d9a4340b..649355158ed435e242a48f4aaa4578bcc2a808dd 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -2171,6 +2171,46 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
}
+ // Paper start - Fix MC-162253
+ /**
+ * Returns the light mask for the given chunk consisting of all non-empty sections that may need sending.
+ */
+ private BitSet lightMask(final LevelChunk chunk) {
+ final net.minecraft.world.level.chunk.LevelChunkSection[] sections = chunk.getSections();
+ final BitSet mask = new BitSet(this.lightEngine.getLightSectionCount());
+
+ // There are 2 more light sections than chunk sections so when iterating over
+ // sections we have to increment the index by 1
+ for (int i = 0; i < sections.length; i++) {
+ if (!sections[i].hasOnlyAir()) {
+ // Whenever a section is not empty, it can change lighting for the section itself (i + 1), the section below, and the section above
+ mask.set(i);
+ mask.set(i + 1);
+ mask.set(i + 2);
+ i++; // We can skip the already set upper section
+ }
+ }
+ return mask;
+ }
+
+ /**
+ * Returns the ceiling light mask of all sections that are equal or lower to the highest non-empty section.
+ */
+ private BitSet ceilingLightMask(final LevelChunk chunk) {
+ final net.minecraft.world.level.chunk.LevelChunkSection[] sections = chunk.getSections();
+ for (int i = sections.length - 1; i >= 0; i--) {
+ if (!sections[i].hasOnlyAir()) {
+ // Add one to get the light section, one because blocks in the section above may change, and another because BitSet's toIndex is exclusive
+ final int highest = i + 3;
+ final BitSet mask = new BitSet(highest);
+ mask.set(0, highest);
+ return mask;
+ }
+ }
+ return new BitSet();
+ }
+ // Paper end - Fix MC-162253
+
// Paper start - Anti-Xray - Bypass
private void playerLoadedChunk(ServerPlayer player, MutableObject<java.util.Map<Object, ClientboundLevelChunkWithLightPacket>> cachedDataPackets, LevelChunk chunk) {
if (cachedDataPackets.getValue() == null) {
@@ -2179,6 +2219,45 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
Boolean shouldModify = chunk.getLevel().chunkPacketBlockController.shouldModify(player, chunk);
player.trackChunk(chunk.getPos(), (Packet) cachedDataPackets.getValue().computeIfAbsent(shouldModify, (s) -> {
+ // Paper start - Fix MC-162253
+ final int viewDistance = getEffectiveViewDistance();
+ final int playerChunkX = player.getBlockX() >> 4;
+ final int playerChunkZ = player.getBlockZ() >> 4;
+
+ // For all loaded neighbours, send sky light for empty sections above highest non-empty section (+1) of the center chunk
+ // otherwise the client will try to calculate lighting there on its own
+ final BitSet lightMask = lightMask(chunk);
+ if (!lightMask.isEmpty()) {
+ for (int x = -1; x <= 1; x++) {
+ for (int z = -1; z <= 1; z++) {
+ if (x == 0 && z == 0) {
+ continue;
+ }
+
+ if (!chunk.isNeighbourLoaded(x, z)) {
+ continue;
+ }
+
+ final int neighborChunkX = chunk.getPos().x + x;
+ final int neighborChunkZ = chunk.getPos().z + z;
+ final int distX = Math.abs(playerChunkX - neighborChunkX);
+ final int distZ = Math.abs(playerChunkZ - neighborChunkZ);
+ if (Math.max(distX, distZ) > viewDistance) {
+ continue;
+ }
+
+ final LevelChunk neighbor = chunk.getRelativeNeighbourIfLoaded(x, z);
+ final BitSet updateLightMask = (BitSet) lightMask.clone();
+ updateLightMask.andNot(ceilingLightMask(neighbor));
+ if (updateLightMask.isEmpty()) {
+ continue;
+ }
+
+ player.connection.send(new net.minecraft.network.protocol.game.ClientboundLightUpdatePacket(new ChunkPos(neighborChunkX, neighborChunkZ), this.lightEngine, updateLightMask, null, true));
+ }
+ }
+ }
+ // Paper end - Fix MC-162253
return new ClientboundLevelChunkWithLightPacket(chunk, this.lightEngine, (BitSet) null, (BitSet) null, true, (Boolean) s);
}));
// Paper end
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