From 63566a507b1b7862d2db89e075914d4c3616d5ea Mon Sep 17 00:00:00 2001
From: minjaesong <alswo9628@gmail.com>
Date: Mon, 19 Jan 2026 17:08:31 +0900
Subject: [PATCH] new: world update ahchoring

---
 src/net/torvald/terrarum/GameCrashHandler.kt  |  73 ++++----
 src/net/torvald/terrarum/IngameInstance.kt    |  16 ++
 .../terrarum/gameactors/WorldUpdateAnchor.kt  |  47 +++++
 .../terrarum/gameactors/WorldUpdater.kt       |  13 ++
 .../terrarum/modulebasegame/TerrarumIngame.kt |  19 +-
 .../terrarum/modulebasegame/WorldSimulator.kt | 177 ++++++++++++++++--
 .../modulebasegame/gameactors/IngamePlayer.kt |   3 +-
 7 files changed, 299 insertions(+), 49 deletions(-)
 create mode 100644 src/net/torvald/terrarum/gameactors/WorldUpdateAnchor.kt
 create mode 100644 src/net/torvald/terrarum/gameactors/WorldUpdater.kt
diff --git a/src/net/torvald/terrarum/GameCrashHandler.kt b/src/net/torvald/terrarum/GameCrashHandler.kt
index a32c6d580..4e6b72b8a 100644
--- a/src/net/torvald/terrarum/GameCrashHandler.kt
+++ b/src/net/torvald/terrarum/GameCrashHandler.kt
@@ -121,6 +121,46 @@ emph {
 
         val uptime = App.getTIME_T() - App.startupTime
 
+
+
+        // print out the error
+        printStream.println("<h3>The Error Info</h3>")
+        System.err.println("== The Error Info ==")
+
+        printStream.println("<pre>")
+        e.printStackTrace(printStream)
+        printStream.println("</pre>")
+        e.printStackTrace(System.err)
+
+
+
+        printStream.println("<h3>Module Info</h3>")
+        printStream.println("<h4>Load Order</h4>")
+        printStream.println("<ol>${ModMgr.loadOrder.joinToString(separator = "") { "<li>" +
+                "$it&ensp;<small>(" +
+                "${moduleMetaToText(ModMgr.moduleInfo[it] ?: ModMgr.moduleInfoErrored[it])}" +
+                ")</small></li>" }
+        }</ol>")
+
+
+
+        // print out loaded modules
+        ModMgr.errorLogs.let {
+            if (it.size > 0) {
+                printStream.println("<h4>Module Errors</h4>")
+                System.err.println("== Module Errors ==")
+                it.forEach {
+                    printStream.println("<p>From Module <strong>${it.moduleName}</strong> (${it.type.toHTML()}):</p>")
+                    printStream.println("<pre>")
+                    it.cause?.printStackTrace(printStream)
+                    printStream.println("</pre>")
+                    it.cause?.printStackTrace(System.err)
+                }
+            }
+        }
+
+
+
         // print out device info
         printStream.println("<h3>System Info</h3>")
         printStream.println("<ul>")
@@ -146,39 +186,6 @@ emph {
             printStream.println("<p><emph>GL not initialised</emph></p>")
         }
 
-        printStream.println("<h3>Module Info</h3>")
-        printStream.println("<h4>Load Order</h4>")
-        printStream.println("<ol>${ModMgr.loadOrder.joinToString(separator = "") { "<li>" +
-                   "$it&ensp;<small>(" +
-                   "${moduleMetaToText(ModMgr.moduleInfo[it] ?: ModMgr.moduleInfoErrored[it])}" +
-                   ")</small></li>" }
-                }</ol>")
-
-
-        ModMgr.errorLogs.let {
-            if (it.size > 0) {
-                printStream.println("<h4>Module Errors</h4>")
-                System.err.println("== Module Errors ==")
-                it.forEach {
-                    printStream.println("<p>From Module <strong>${it.moduleName}</strong> (${it.type.toHTML()}):</p>")
-                    printStream.println("<pre>")
-                    it.cause?.printStackTrace(printStream)
-                    printStream.println("</pre>")
-                    it.cause?.printStackTrace(System.err)
-                }
-            }
-        }
-
-        printStream.println("<h3>The Error Info</h3>")
-        System.err.println("== The Error Info ==")
-
-        printStream.println("<pre>")
-        e.printStackTrace(printStream)
-        printStream.println("</pre>")
-        e.printStackTrace(System.err)
-
-
-
         textArea.text = "<html><style type=\"text/css\">$css</style><body>$htmlSB</body></html>"
     }
 
diff --git a/src/net/torvald/terrarum/IngameInstance.kt b/src/net/torvald/terrarum/IngameInstance.kt
index c40ad3480..b0ea0e1d6 100644
--- a/src/net/torvald/terrarum/IngameInstance.kt
+++ b/src/net/torvald/terrarum/IngameInstance.kt
@@ -8,6 +8,7 @@ import net.torvald.terrarum.gameactors.ActorID
 import net.torvald.terrarum.gameactors.ActorWithBody
 import net.torvald.terrarum.gameactors.ActorWithBody.Companion.PHYS_EPSILON_DIST
 import net.torvald.terrarum.gameactors.BlockMarkerActor
+import net.torvald.terrarum.gameactors.WorldUpdater
 import net.torvald.terrarum.gamecontroller.KeyToggler
 import net.torvald.terrarum.gamecontroller.TerrarumKeyboardEvent
 import net.torvald.terrarum.gameitems.ItemID
@@ -147,6 +148,13 @@ open class IngameInstance(val batch: FlippingSpriteBatch, val isMultiplayer: Boo
     val actorAdditionQueue = ArrayList<Triple<Actor, Throwable, (Actor) -> Unit>>() // actor, stacktrace object, onSpawn
     val actorRemovalQueue = ArrayList<Triple<Actor, Throwable, (Actor) -> Unit>>() // actor, stacktrace object, onDespawn
 
+    /**
+     * Registry of actors that implement [WorldUpdater].
+     * World simulation (fluids, wires, tile updates) is active around these actors.
+     * Automatically maintained when actors are added/removed.
+     */
+    val worldUpdaters: MutableSet<ActorWithBody> = HashSet()
+
     /**
      * ## BIG NOTE: Calculated actor distance is the **Euclidean distance SQUARED**
      *
@@ -378,6 +386,10 @@ open class IngameInstance(val batch: FlippingSpriteBatch, val isMultiplayer: Boo
                 actorContainer.removeAt(indexToDelete)
             }
         }
+        // Unregister from worldUpdaters if applicable
+        if (actor is WorldUpdater && actor is ActorWithBody) {
+            worldUpdaters.remove(actor)
+        }
     }
 
     protected open fun forceAddActor(actor: Actor?, caller: Throwable = StackTraceRecorder()) {
@@ -388,6 +400,10 @@ open class IngameInstance(val batch: FlippingSpriteBatch, val isMultiplayer: Boo
         }
         else {
             actorContainerActive.add(actor)
+            // Register to worldUpdaters if applicable
+            if (actor is WorldUpdater && actor is ActorWithBody) {
+                worldUpdaters.add(actor)
+            }
         }
     }
 
diff --git a/src/net/torvald/terrarum/gameactors/WorldUpdateAnchor.kt b/src/net/torvald/terrarum/gameactors/WorldUpdateAnchor.kt
new file mode 100644
index 000000000..0db3ed48d
--- /dev/null
+++ b/src/net/torvald/terrarum/gameactors/WorldUpdateAnchor.kt
@@ -0,0 +1,47 @@
+package net.torvald.terrarum.gameactors
+
+import com.badlogic.gdx.graphics.g2d.SpriteBatch
+
+/**
+ * Minimal anchor actor for world updates.
+ *
+ * This actor has no visible representation and does not participate in physics.
+ * It serves purely as a point around which world simulation (fluids, wires, tile updates)
+ * remains active.
+ *
+ * Created by minjaesong on 2026-01-19.
+ */
+class WorldUpdateAnchor : ActorWithBody, WorldUpdater, NoSerialise {
+
+    constructor() : super(RenderOrder.MIDDLE, PhysProperties.IMMOBILE()) {
+        isVisible = false
+        chunkAnchoring = true
+        setHitboxDimension(1, 1, 0, 0)
+    }
+
+    constructor(id: ActorID) : super(RenderOrder.MIDDLE, PhysProperties.IMMOBILE(), id) {
+        isVisible = false
+        chunkAnchoring = true
+        setHitboxDimension(1, 1, 0, 0)
+    }
+
+    override fun updateImpl(delta: Float) {
+        // No-op; this actor exists solely as a world update anchor
+    }
+
+    override fun drawBody(frameDelta: Float, batch: SpriteBatch) {
+        // No-op; this actor is invisible
+    }
+
+    override fun drawGlow(frameDelta: Float, batch: SpriteBatch) {
+        // No-op; this actor is invisible
+    }
+
+    override fun drawEmissive(frameDelta: Float, batch: SpriteBatch) {
+        // No-op; this actor is invisible
+    }
+
+    override fun dispose() {
+        // Nothing to dispose
+    }
+}
diff --git a/src/net/torvald/terrarum/gameactors/WorldUpdater.kt b/src/net/torvald/terrarum/gameactors/WorldUpdater.kt
new file mode 100644
index 000000000..e332c72e9
--- /dev/null
+++ b/src/net/torvald/terrarum/gameactors/WorldUpdater.kt
@@ -0,0 +1,13 @@
+package net.torvald.terrarum.gameactors
+
+/**
+ * Marker interface for actors that serve as "world update anchors".
+ *
+ * Actors implementing this interface cause world simulation (fluids, wires, tile updates)
+ * to be active in their vicinity, regardless of camera position.
+ *
+ * All implementations must also extend [ActorWithBody].
+ *
+ * Created by minjaesong on 2026-01-19.
+ */
+interface WorldUpdater
diff --git a/src/net/torvald/terrarum/modulebasegame/TerrarumIngame.kt b/src/net/torvald/terrarum/modulebasegame/TerrarumIngame.kt
index a97bb9667..25cff4004 100644
--- a/src/net/torvald/terrarum/modulebasegame/TerrarumIngame.kt
+++ b/src/net/torvald/terrarum/modulebasegame/TerrarumIngame.kt
@@ -150,8 +150,23 @@ open class TerrarumIngame(batch: FlippingSpriteBatch) : IngameInstance(batch) {
                         (a.hitbox.centeredY - WorldCamera.yCentre).sqr()
                 )
 
-        /** whether the actor is within update range */
-        fun ActorWithBody.inUpdateRange(world: GameWorld) = distToCameraSqr(world, this) <= ACTOR_UPDATE_RANGE.sqr()
+        /**
+         * Returns the minimum squared distance from the actor to any living WorldUpdater.
+         * Falls back to camera distance if no WorldUpdaters exist.
+         */
+        fun distToNearestUpdaterSqr(world: GameWorld, actor: ActorWithBody): Double {
+            val worldUpdaters = Terrarum.ingame?.worldUpdaters
+            if (worldUpdaters.isNullOrEmpty()) {
+                return distToCameraSqr(world, actor)
+            }
+            return worldUpdaters.minOf { updater ->
+                if (updater.flagDespawn || updater.despawned) Double.MAX_VALUE
+                else distToActorSqr(world, actor, updater)
+            }
+        }
+
+        /** whether the actor is within update range of any WorldUpdater */
+        fun ActorWithBody.inUpdateRange(world: GameWorld) = distToNearestUpdaterSqr(world, this) <= ACTOR_UPDATE_RANGE.sqr()
 
         /** whether the actor is within screen */
         fun ActorWithBody.inScreen(world: GameWorld) =
diff --git a/src/net/torvald/terrarum/modulebasegame/WorldSimulator.kt b/src/net/torvald/terrarum/modulebasegame/WorldSimulator.kt
index da18c7250..29d8a34b8 100644
--- a/src/net/torvald/terrarum/modulebasegame/WorldSimulator.kt
+++ b/src/net/torvald/terrarum/modulebasegame/WorldSimulator.kt
@@ -23,6 +23,7 @@ import net.torvald.terrarum.realestate.LandUtil.CHUNK_H
 import net.torvald.terrarum.realestate.LandUtil.CHUNK_W
 import org.dyn4j.geometry.Vector2
 import kotlin.math.cosh
+import kotlin.math.max
 import kotlin.math.min
 import kotlin.math.pow
 import kotlin.math.roundToInt
@@ -50,6 +51,9 @@ object WorldSimulator {
     private val fluidNewMap = Array(DOUBLE_RADIUS) { FloatArray(DOUBLE_RADIUS) }
     private val fluidNewTypeMap = Array(DOUBLE_RADIUS) { Array(DOUBLE_RADIUS) { Fluid.NULL } }
 
+    // Mask to track tiles that have already been fluid-simulated this frame (for overlap deduplication)
+    private val processedFluidTiles = HashSet<Long>()
+
     const val FLUID_MAX_MASS = 1f // The normal, un-pressurized mass of a full water cell
     const val FLUID_MAX_COMP = 0.01f // How much excess water a cell can store, compared to the cell above it. A tile of fluid can contain more than MaxMass water.
 //    const val FLUID_MIN_MASS = net.torvald.terrarum.gameworld.FLUID_MIN_MASS //Ignore cells that are almost dry (smaller than epsilon of float16)
@@ -66,6 +70,97 @@ object WorldSimulator {
     /** Bottom-right point */
     var updateYTo = 0
 
+    /**
+     * Represents a rectangular region for world updates.
+     */
+    data class UpdateRegion(val xFrom: Int, val yFrom: Int, val xTo: Int, val yTo: Int) {
+        fun overlaps(other: UpdateRegion): Boolean {
+            return xFrom <= other.xTo && xTo >= other.xFrom &&
+                   yFrom <= other.yTo && yTo >= other.yFrom
+        }
+
+        fun merge(other: UpdateRegion): UpdateRegion {
+            return UpdateRegion(
+                min(xFrom, other.xFrom),
+                min(yFrom, other.yFrom),
+                max(xTo, other.xTo),
+                max(yTo, other.yTo)
+            )
+        }
+
+        val width get() = xTo - xFrom
+        val height get() = yTo - yFrom
+    }
+
+    /**
+     * Merges overlapping regions into non-overlapping ones.
+     * Uses iterative merging until no more merges are possible.
+     */
+    private fun mergeOverlappingRegions(regions: List<UpdateRegion>): List<UpdateRegion> {
+        if (regions.size <= 1) return regions
+
+        val result = regions.toMutableList()
+        var merged = true
+        while (merged) {
+            merged = false
+            outer@ for (i in result.indices) {
+                for (j in i + 1 until result.size) {
+                    if (result[i].overlaps(result[j])) {
+                        val mergedRegion = result[i].merge(result[j])
+                        result.removeAt(j)
+                        result[i] = mergedRegion
+                        merged = true
+                        break@outer
+                    }
+                }
+            }
+        }
+        return result
+    }
+
+    /**
+     * Computes update regions from all living WorldUpdaters.
+     * Returns a list of non-overlapping merged regions.
+     */
+    private fun computeUpdateRegions(): List<UpdateRegion> {
+        val worldUpdaters = ingame.worldUpdaters.filter { !it.flagDespawn && !it.despawned }
+        if (worldUpdaters.isEmpty()) return emptyList()
+
+        val regions = worldUpdaters.map { updater ->
+            val cx = updater.hitbox.centeredX.div(TILE_SIZE).roundToInt()
+            val cy = updater.hitbox.centeredY.div(TILE_SIZE).roundToInt()
+            UpdateRegion(
+                cx - FLUID_UPDATING_SQUARE_RADIUS,
+                cy - FLUID_UPDATING_SQUARE_RADIUS,
+                cx + FLUID_UPDATING_SQUARE_RADIUS,
+                cy + FLUID_UPDATING_SQUARE_RADIUS
+            )
+        }
+
+        return mergeOverlappingRegions(regions)
+    }
+
+    /**
+     * Computes individual (unmerged) fluid regions for each WorldUpdater.
+     * Each region is exactly DOUBLE_RADIUS × DOUBLE_RADIUS to fit the fixed fluid arrays.
+     * Overlap deduplication is handled by processedFluidTiles mask during fluidmapToWorld().
+     */
+    private fun computeIndividualFluidRegions(): List<UpdateRegion> {
+        val worldUpdaters = ingame.worldUpdaters.filter { !it.flagDespawn && !it.despawned }
+        if (worldUpdaters.isEmpty()) return emptyList()
+
+        return worldUpdaters.map { updater ->
+            val cx = updater.hitbox.centeredX.div(TILE_SIZE).roundToInt()
+            val cy = updater.hitbox.centeredY.div(TILE_SIZE).roundToInt()
+            UpdateRegion(
+                cx - FLUID_UPDATING_SQUARE_RADIUS,
+                cy - FLUID_UPDATING_SQUARE_RADIUS,
+                cx + FLUID_UPDATING_SQUARE_RADIUS,
+                cy + FLUID_UPDATING_SQUARE_RADIUS
+            )
+        }
+    }
+
     private val ingame: TerrarumIngame
             get() = Terrarum.ingame!! as TerrarumIngame
     private val world: GameWorld
@@ -82,21 +177,66 @@ object WorldSimulator {
 
         //printdbg(this, "============================")
 
-        if (player != null) {
-            updateXFrom = player.hitbox.centeredX.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
-            updateYFrom = player.hitbox.centeredY.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
-            updateXTo = updateXFrom + DOUBLE_RADIUS
-            updateYTo = updateYFrom + DOUBLE_RADIUS
+        // Compute non-overlapping merged regions for general simulations
+        val mergedRegions = computeUpdateRegions()
+
+        // Compute individual (unmerged) regions for fluid simulation
+        // Each WorldUpdater gets its own fluid region; overlap is handled by processedFluidTiles mask
+        val fluidRegions = computeIndividualFluidRegions()
+
+        // Fallback to player-based region if no WorldUpdaters exist
+        val regionsToProcess = if (mergedRegions.isNotEmpty()) {
+            mergedRegions
+        } else if (player != null) {
+            val px = player.hitbox.centeredX.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
+            val py = player.hitbox.centeredY.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
+            listOf(UpdateRegion(px, py, px + DOUBLE_RADIUS, py + DOUBLE_RADIUS))
+        } else {
+            emptyList()
         }
 
-        if (ingame.terrainChangeQueue.isNotEmpty()) { App.measureDebugTime("WorldSimulator.degrass") { buryGrassImmediately() } }
-        App.measureDebugTime("WorldSimulator.growGrass") { growOrKillGrass() }
-        App.measureDebugTime("WorldSimulator.fluids") { moveFluids(delta) }
-        App.measureDebugTime("WorldSimulator.fallables") { displaceFallables(delta) }
-        App.measureDebugTime("WorldSimulator.wires") { simulateWires(delta) }
-        App.measureDebugTime("WorldSimulator.collisionDroppedItem") { collideDroppedItems() }
-        App.measureDebugTime("WorldSimulator.dropTreeLeaves") { dropTreeLeaves() }
+        val fluidRegionsToProcess = if (fluidRegions.isNotEmpty()) {
+            fluidRegions
+        } else if (player != null) {
+            val px = player.hitbox.centeredX.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
+            val py = player.hitbox.centeredY.div(TILE_SIZE).minus(FLUID_UPDATING_SQUARE_RADIUS).roundToInt()
+            listOf(UpdateRegion(px, py, px + DOUBLE_RADIUS, py + DOUBLE_RADIUS))
+        } else {
+            emptyList()
+        }
 
+        // buryGrassImmediately doesn't depend on update region
+        if (ingame.terrainChangeQueue.isNotEmpty()) {
+            App.measureDebugTime("WorldSimulator.degrass") { buryGrassImmediately() }
+        }
+
+        // Process fluids for each WorldUpdater individually, using mask for overlap deduplication
+        processedFluidTiles.clear()
+        App.measureDebugTime("WorldSimulator.fluids") {
+            for (region in fluidRegionsToProcess) {
+                updateXFrom = region.xFrom
+                updateYFrom = region.yFrom
+                updateXTo = region.xTo
+                updateYTo = region.yTo
+                moveFluids(delta)
+            }
+        }
+
+        // Process other simulations using merged non-overlapping regions
+        for (region in regionsToProcess) {
+            updateXFrom = region.xFrom
+            updateYFrom = region.yFrom
+            updateXTo = region.xTo
+            updateYTo = region.yTo
+
+            App.measureDebugTime("WorldSimulator.growGrass") { growOrKillGrass() }
+            App.measureDebugTime("WorldSimulator.fallables") { displaceFallables(delta) }
+            App.measureDebugTime("WorldSimulator.wires") { simulateWires(delta) }
+            App.measureDebugTime("WorldSimulator.dropTreeLeaves") { dropTreeLeaves() }
+        }
+
+        // collideDroppedItems doesn't depend on update region (uses actor list)
+        App.measureDebugTime("WorldSimulator.collisionDroppedItem") { collideDroppedItems() }
 
         //printdbg(this, "============================")
     }
@@ -502,10 +642,21 @@ object WorldSimulator {
         }
     }
 
+    /** Packs world coordinates into a single Long for use as a HashSet key */
+    private fun packFluidCoords(worldX: Int, worldY: Int): Long =
+        (worldX.toLong() shl 32) or (worldY.toLong() and 0xFFFFFFFFL)
+
     private fun fluidmapToWorld() {
         for (y in fluidMap.indices) {
             for (x in fluidMap[0].indices) {
-                world.setFluid(x + updateXFrom, y + updateYFrom, fluidNewTypeMap[y][x], fluidNewMap[y][x])
+                val worldX = x + updateXFrom
+                val worldY = y + updateYFrom
+                val key = packFluidCoords(worldX, worldY)
+                // Only write if this tile hasn't been processed yet (deduplication for overlapping regions)
+                if (key !in processedFluidTiles) {
+                    world.setFluid(worldX, worldY, fluidNewTypeMap[y][x], fluidNewMap[y][x])
+                    processedFluidTiles.add(key)
+                }
             }
         }
     }
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/IngamePlayer.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/IngamePlayer.kt
index e5a180d0c..c90ababaa 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/IngamePlayer.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/IngamePlayer.kt
@@ -7,6 +7,7 @@ import net.torvald.terrarum.App
 import net.torvald.terrarum.Terrarum
 import net.torvald.terrarum.gameactors.AVKey
 import net.torvald.terrarum.gameactors.NoSerialise
+import net.torvald.terrarum.gameactors.WorldUpdater
 import net.torvald.terrarum.itemproperties.ItemRemapTable
 import net.torvald.terrarum.itemproperties.ItemTable
 import net.torvald.terrarum.spriteassembler.ADProperties
@@ -20,7 +21,7 @@ import java.util.*
  * Created by minjaesong on 2015-12-31.
  */
 
-class IngamePlayer : ActorHumanoid, HasAssembledSprite, NoSerialise {
+class IngamePlayer : ActorHumanoid, HasAssembledSprite, NoSerialise, WorldUpdater {
 
     val creationTime = App.getTIME_T()
     var lastPlayTime = App.getTIME_T() // cumulative value for the savegame
