wire sim refactor

src/net/torvald/terrarum/gameactors/WireActor.kt

@@ -97,7 +97,8 @@ class WireActor : ActorWithBody, NoSerialise, InternalActor {
 
             // signal wires?
             if (WireCodex.wireProps[wireID]?.accepts == "digital_bit") {
-                val strength = world?.getWireEmitStateOf(worldX, worldY, wireID)?.x ?: 0.0
+                // Use parametric brightness from logical wire graph for efficiency
+                val strength = world?.getWireBrightness(worldX, worldY, wireID) ?: 0.0
 
                 // draw base (unlit) sprite
                 batch.color = Color.WHITE

src/net/torvald/terrarum/gameworld/GameWorld.kt

@@ -122,6 +122,13 @@ open class GameWorld(
     public val wirings = HashedWirings()
     private val wiringGraph = HashedWiringGraph()
 
+    /**
+     * Logical wire graph for efficient signal propagation.
+     * Contains coarse graph with logical nodes (fixtures, junctions) and segments.
+     * Rebuilt when wires are placed/removed; used for signal simulation and brightness lookup.
+     */
+    val logicalWireGraph: LogicalWireGraph by lazy { LogicalWireGraph(this) }
+
     @Transient private val WIRE_POS_MAP = intArrayOf(1,2,4,8)
     @Transient private val WIRE_ANTIPOS_MAP = intArrayOf(4,8,1,2)
 
@@ -540,6 +547,10 @@ open class GameWorld(
 
         // scratch-that-i'll-figure-it-out wire placement
         setWireGraphOfUnsafe(blockAddr, tile, connection)
+
+        // Note: Do NOT rebuild logical wire graph here - connectivity is set up
+        // separately by BlockBase.setConnectivity() AFTER this call.
+        // The graph is rebuilt at the end of wire placement in BlockBase.kt
     }
 
     fun setTileOnLayerUnsafe(layer: Int, x: Int, y: Int, tile: Int) {
@@ -569,6 +580,9 @@ open class GameWorld(
             // remove wire from this tile
             wiringGraph[blockAddr]!!.remove(tile)
             wirings[blockAddr]!!.ws.remove(tile)
+
+            // Rebuild logical wire graph for this wire type
+            logicalWireGraph.rebuild(tile)
         }
     }
 
@@ -586,6 +600,9 @@ open class GameWorld(
             // remove wire from this tile
             wiringGraph[blockAddr]!!.remove(tile)
             wirings[blockAddr]!!.ws.remove(tile)
+
+            // Rebuild logical wire graph for this wire type
+            logicalWireGraph.rebuild(tile)
         }
     }
 
@@ -609,6 +626,27 @@ open class GameWorld(
         return wiringGraph[blockAddr]?.get(itemID)?.emt
     }
 
+    /**
+     * Get wire brightness using parametric evaluation from the logical wire graph.
+     * This is more efficient than per-tile signal storage as it derives brightness
+     * from segment properties rather than storing it per-tile.
+     *
+     * @param x World tile X coordinate
+     * @param y World tile Y coordinate
+     * @param wireType The wire item ID
+     * @return Signal strength at this position (0.0 to 1.0+), or 0.0 if no wire/signal
+     */
+    fun getWireBrightness(x: Int, y: Int, wireType: ItemID): Double {
+        val (cx, cy) = coerceXY(x, y)
+        val blockAddr = LandUtil.getBlockAddr(this, cx, cy)
+
+        val segment = logicalWireGraph.getGraph(wireType)
+            ?.positionToSegment?.get(blockAddr) ?: return 0.0
+
+        val offset = segment.getOffsetForPosition(Point2i(cx, cy)) ?: return 0.0
+        return segment.getBrightnessAtOffset(offset)
+    }
+
     fun getWireReceptionStateOf(x: Int, y: Int, itemID: ItemID): ArrayList<WireReceptionState>? {
         val (x, y) = coerceXY(x, y)
         val blockAddr = LandUtil.getBlockAddr(this, x, y)

src/net/torvald/terrarum/gameworld/LogicalWireGraph.kt

@@ -0,0 +1,491 @@
+package net.torvald.terrarum.gameworld
+
+import net.torvald.terrarum.INGAME
+import net.torvald.terrarum.Point2i
+import net.torvald.terrarum.WireCodex
+import net.torvald.terrarum.gameitems.ItemID
+import net.torvald.terrarum.modulebasegame.TerrarumIngame.Companion.inUpdateRange
+import net.torvald.terrarum.modulebasegame.gameactors.Electric
+import net.torvald.terrarum.modulebasegame.gameactors.WireEmissionType
+import net.torvald.terrarum.realestate.LandUtil
+import org.dyn4j.geometry.Vector2
+import kotlin.math.pow
+
+/**
+ * Two-layer wire simulation model: Logical graph for signal propagation.
+ *
+ * The logical graph separates "what changes per tile" (visual brightness) from
+ * "what doesn't" (connectivity topology, signal evaluation). This reduces
+ * simulation complexity from O(wire_tiles) to O(logical_nodes).
+ *
+ * Logical nodes are:
+ * - Signal sources (fixtures with wireEmitterTypes)
+ * - Signal sinks (fixtures with wireSinkTypes)
+ * - Junctions (wire tiles with 3+ connections)
+ *
+ * Wire segments connect logical nodes. Signal propagates along segments with
+ * decay calculated per-segment, not per-tile.
+ *
+ * Created for Terrarum wire simulation refactoring.
+ *
+ * Created by minjaesong and Claude on 2026-01-08.
+ */
+
+typealias BlockBoxIndex = Int
+
+/**
+ * Represents a node in the logical wire graph.
+ * Nodes are: signal sources, signal sinks, and junctions (3+ connections).
+ */
+sealed class LogicalWireNode {
+    abstract val position: Point2i
+    abstract val wireType: ItemID
+    abstract var signalStrength: Vector2
+
+    /** Connected segments (populated during graph building) */
+    @Transient
+    val connectedSegments: MutableList<WireSegment> = mutableListOf()
+
+    /**
+     * Fixture-backed node (source or sink).
+     * References the Electric fixture that emits or receives signals.
+     */
+    data class FixtureNode(
+        override val position: Point2i,
+        override val wireType: ItemID,
+        val fixtureRef: Electric,
+        val blockBoxIndex: BlockBoxIndex,
+        val isEmitter: Boolean,
+        val emissionType: WireEmissionType
+    ) : LogicalWireNode() {
+        override var signalStrength: Vector2 = Vector2(0.0, 0.0)
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (other !is FixtureNode) return false
+            return position == other.position && wireType == other.wireType &&
+                    blockBoxIndex == other.blockBoxIndex && isEmitter == other.isEmitter
+        }
+
+        override fun hashCode(): Int {
+            var result = position.hashCode()
+            result = 31 * result + wireType.hashCode()
+            result = 31 * result + blockBoxIndex
+            result = 31 * result + isEmitter.hashCode()
+            return result
+        }
+    }
+
+    /**
+     * Junction node where 3+ wire segments meet.
+     * Acts as a signal relay point with potential splitting/merging.
+     */
+    data class JunctionNode(
+        override val position: Point2i,
+        override val wireType: ItemID,
+        val connectionCount: Int  // 3 for T-junction, 4 for cross
+    ) : LogicalWireNode() {
+        override var signalStrength: Vector2 = Vector2(0.0, 0.0)
+
+        override fun equals(other: Any?): Boolean {
+            if (this === other) return true
+            if (other !is JunctionNode) return false
+            return position == other.position && wireType == other.wireType
+        }
+
+        override fun hashCode(): Int {
+            var result = position.hashCode()
+            result = 31 * result + wireType.hashCode()
+            return result
+        }
+    }
+}
+
+/**
+ * Represents a wire segment connecting two logical nodes.
+ * Signal decays along the segment based on length.
+ *
+ * Replaces N tile nodes with a single edge, enabling O(1) signal propagation
+ * across an entire wire run.
+ */
+data class WireSegment(
+    val wireType: ItemID,
+    var startNode: LogicalWireNode,
+    var endNode: LogicalWireNode,
+    val length: Int,
+    val tilePositions: List<Point2i>,
+    var startStrength: Double = 0.0,
+    var endStrength: Double = 0.0,
+    val decayConstant: Double = 1.0
+) {
+    /**
+     * Parametric brightness evaluation - O(1) per tile.
+     * @param offset Distance from start node (0 to length)
+     * @return Signal strength at that offset
+     */
+    fun getBrightnessAtOffset(offset: Int): Double {
+        if (offset < 0 || offset > length) return 0.0
+        // Calculate from whichever end has the stronger signal
+        val fromStart = startStrength * decayConstant.pow(offset.toDouble())
+        val fromEnd = endStrength * decayConstant.pow((length - offset).toDouble())
+        return maxOf(fromStart, fromEnd).coerceAtLeast(0.0)
+    }
+
+    /**
+     * Get the offset of a tile position within this segment.
+     * @return Offset index, or null if position not in segment
+     */
+    fun getOffsetForPosition(pos: Point2i): Int? {
+        val idx = tilePositions.indexOfFirst { it.x == pos.x && it.y == pos.y }
+        return if (idx >= 0) idx else null
+    }
+
+    /**
+     * Get the node at the other end of this segment.
+     */
+    fun getOtherEnd(node: LogicalWireNode): LogicalWireNode {
+        return if (node === startNode || node == startNode) endNode else startNode
+    }
+}
+
+/**
+ * Complete logical wire graph for a world.
+ * Stored per wire-type for efficiency.
+ */
+class LogicalWireGraph(private val world: GameWorld) {
+
+    companion object {
+        private const val RIGHT = 1
+        private const val DOWN = 2
+        private const val LEFT = 4
+        private const val UP = 8
+
+        private val DIRECTIONS = intArrayOf(RIGHT, DOWN, LEFT, UP)
+        private val DIRECTION_OFFSETS = mapOf(
+            RIGHT to Point2i(1, 0),
+            DOWN to Point2i(0, 1),
+            LEFT to Point2i(-1, 0),
+            UP to Point2i(0, -1)
+        )
+
+        private fun Int.wireNodeMirror(): Int = when (this) {
+            RIGHT -> LEFT
+            DOWN -> UP
+            LEFT -> RIGHT
+            UP -> DOWN
+            else -> 0
+        }
+    }
+
+    /**
+     * Graph data for a single wire type.
+     */
+    data class WireTypeGraph(
+        val nodes: MutableList<LogicalWireNode> = mutableListOf(),
+        val segments: MutableList<WireSegment> = mutableListOf(),
+        val positionToSegment: HashMap<BlockAddress, WireSegment> = HashMap(),
+        val positionToNode: HashMap<BlockAddress, LogicalWireNode> = HashMap(),
+        var dirty: Boolean = true,
+        var structureDirty: Boolean = true  // Set when fixtures are added/removed; requires full rebuild
+    ) {
+        fun clear() {
+            nodes.forEach { it.connectedSegments.clear() }
+            nodes.clear()
+            segments.clear()
+            positionToSegment.clear()
+            positionToNode.clear()
+            dirty = true
+            structureDirty = false  // We're about to rebuild, so structure will be fresh
+        }
+    }
+
+    private val graphs = HashMap<ItemID, WireTypeGraph>()
+
+    fun getGraph(wireType: ItemID): WireTypeGraph? = graphs[wireType]
+
+    fun getOrCreateGraph(wireType: ItemID): WireTypeGraph {
+        return graphs.getOrPut(wireType) { WireTypeGraph() }
+    }
+
+    fun markDirty(wireType: ItemID) {
+        graphs[wireType]?.dirty = true
+    }
+
+    fun markAllDirty() {
+        graphs.values.forEach { it.dirty = true }
+    }
+
+    /**
+     * Mark all graphs as needing structural rebuild.
+     * Called when Electric fixtures are spawned or despawned.
+     */
+    fun markAllStructureDirty() {
+        graphs.values.forEach { it.structureDirty = true }
+    }
+
+    /**
+     * Rebuild the logical graph for a specific wire type.
+     * Scans all wire tiles and fixtures to construct nodes and segments.
+     */
+    fun rebuild(wireType: ItemID) {
+        val graph = getOrCreateGraph(wireType)
+        graph.clear()
+
+        val emissionType = WireCodex[wireType].accepts
+        val decayConstant = WireCodex.wireDecays[wireType] ?: 1.0
+
+        // Step 1: Find all logical nodes
+
+        // 1a: Fixture nodes (emitters and sinks)
+        INGAME.actorContainerActive.filterIsInstance<Electric>().forEach { fixture ->
+            if (!fixture.inUpdateRange(world)) return@forEach
+
+            // Emitter ports
+            fixture.wireEmitterTypes.forEach { (bbi, wireEmissionType) ->
+                if (wireEmissionType == emissionType) {
+                    val pos = fixture.worldBlockPos!! + fixture.blockBoxIndexToPoint2i(bbi)
+                    // Only add if there's actually a wire at this position
+                    if (hasWireAt(pos.x, pos.y, wireType)) {
+                        val node = LogicalWireNode.FixtureNode(
+                            position = pos,
+                            wireType = wireType,
+                            fixtureRef = fixture,
+                            blockBoxIndex = bbi,
+                            isEmitter = true,
+                            emissionType = wireEmissionType
+                        )
+                        graph.nodes.add(node)
+                        graph.positionToNode[LandUtil.getBlockAddr(world, pos.x, pos.y)] = node
+                    }
+                }
+            }
+
+            // Sink ports
+            fixture.wireSinkTypes.forEach { (bbi, wireSinkType) ->
+                if (wireSinkType == emissionType) {
+                    val pos = fixture.worldBlockPos!! + fixture.blockBoxIndexToPoint2i(bbi)
+                    if (hasWireAt(pos.x, pos.y, wireType)) {
+                        val blockAddr = LandUtil.getBlockAddr(world, pos.x, pos.y)
+                        // Don't add duplicate node if already an emitter at same position
+                        if (!graph.positionToNode.containsKey(blockAddr)) {
+                            val node = LogicalWireNode.FixtureNode(
+                                position = pos,
+                                wireType = wireType,
+                                fixtureRef = fixture,
+                                blockBoxIndex = bbi,
+                                isEmitter = false,
+                                emissionType = wireSinkType
+                            )
+                            graph.nodes.add(node)
+                            graph.positionToNode[blockAddr] = node
+                        }
+                    }
+                }
+            }
+        }
+
+        // 1b: Junction nodes (tiles with 3+ connections)
+        world.wirings.forEach { (blockAddr, wiringNode) ->
+            if (wiringNode.ws.contains(wireType)) {
+                val cnx = world.getWireGraphUnsafe(blockAddr, wireType) ?: 0
+                val connectionCount = Integer.bitCount(cnx)
+
+                if (connectionCount >= 3) {
+                    val x = (blockAddr % world.width).toInt()
+                    val y = (blockAddr / world.width).toInt()
+
+                    // Don't create junction if there's already a fixture node here
+                    if (!graph.positionToNode.containsKey(blockAddr)) {
+                        val node = LogicalWireNode.JunctionNode(
+                            position = Point2i(x, y),
+                            wireType = wireType,
+                            connectionCount = connectionCount
+                        )
+                        graph.nodes.add(node)
+                        graph.positionToNode[blockAddr] = node
+                    }
+                }
+            }
+        }
+
+        // Step 2: Trace segments between nodes
+        val visitedEdges = HashSet<Pair<BlockAddress, Int>>()  // (position, direction)
+
+        graph.nodes.forEach { startNode ->
+            val startAddr = LandUtil.getBlockAddr(world, startNode.position.x, startNode.position.y)
+            val cnx = world.getWireGraphUnsafe(startAddr, wireType) ?: 0
+
+            for (dir in DIRECTIONS) {
+                if (cnx and dir != 0) {
+                    val edgeKey = startAddr to dir
+                    if (visitedEdges.contains(edgeKey)) continue
+
+                    // Trace path in this direction
+                    val segment = tracePath(startNode, dir, wireType, decayConstant, graph.positionToNode)
+
+                    if (segment != null) {
+                        graph.segments.add(segment)
+                        startNode.connectedSegments.add(segment)
+                        segment.endNode.connectedSegments.add(segment)
+
+                        // Mark all tiles in segment
+                        segment.tilePositions.forEach { pos ->
+                            val addr = LandUtil.getBlockAddr(world, pos.x, pos.y)
+                            graph.positionToSegment[addr] = segment
+                        }
+
+                        // Mark both directions as visited
+                        val endAddr = LandUtil.getBlockAddr(world, segment.endNode.position.x, segment.endNode.position.y)
+                        visitedEdges.add(startAddr to dir)
+                        visitedEdges.add(endAddr to dir.wireNodeMirror())
+                    }
+                }
+            }
+        }
+
+        // Handle orphan wire tiles (connected to nothing) - create single-tile segments
+        world.wirings.forEach { (blockAddr, wiringNode) ->
+            if (wiringNode.ws.contains(wireType) && !graph.positionToSegment.containsKey(blockAddr)) {
+                val x = (blockAddr % world.width).toInt()
+                val y = (blockAddr / world.width).toInt()
+                val pos = Point2i(x, y)
+
+                // Create a degenerate segment for orphan tiles
+                val orphanNode = LogicalWireNode.JunctionNode(pos, wireType, 0)
+                val segment = WireSegment(
+                    wireType = wireType,
+                    startNode = orphanNode,
+                    endNode = orphanNode,
+                    length = 0,
+                    tilePositions = listOf(pos),
+                    decayConstant = decayConstant
+                )
+                graph.segments.add(segment)
+                graph.positionToSegment[blockAddr] = segment
+            }
+        }
+
+        graph.dirty = true
+    }
+
+    /**
+     * Trace a wire path from a node in a given direction until hitting another node.
+     */
+    private fun tracePath(
+        startNode: LogicalWireNode,
+        initialDirection: Int,
+        wireType: ItemID,
+        decayConstant: Double,
+        positionToNode: HashMap<BlockAddress, LogicalWireNode>
+    ): WireSegment? {
+        val path = mutableListOf<Point2i>()
+        path.add(startNode.position)
+
+        var currentPos = startNode.position
+        var direction = initialDirection
+
+        // Move to first tile in the direction
+        val offset = DIRECTION_OFFSETS[direction] ?: return null
+        currentPos = Point2i(currentPos.x + offset.x, currentPos.y + offset.y)
+
+        val maxIterations = 100000  // Safety limit
+        var iterations = 0
+
+        while (iterations++ < maxIterations) {
+            val blockAddr = LandUtil.getBlockAddr(world, currentPos.x, currentPos.y)
+
+            // Check if we've reached another logical node
+            val endNode = positionToNode[blockAddr]
+            if (endNode != null && endNode !== startNode) {
+                path.add(currentPos)
+                return WireSegment(
+                    wireType = wireType,
+                    startNode = startNode,
+                    endNode = endNode,
+                    length = path.size - 1,  // Length is number of edges, not vertices
+                    tilePositions = path.toList(),
+                    decayConstant = decayConstant
+                )
+            }
+
+            // Check if wire exists here
+            val cnx = world.getWireGraphUnsafe(blockAddr, wireType)
+            if (cnx == null || cnx == 0) {
+                // Dead end - create endpoint node
+                val deadEndNode = LogicalWireNode.JunctionNode(
+                    position = Point2i(currentPos.x, currentPos.y),
+                    wireType = wireType,
+                    connectionCount = 1
+                )
+                // Note: we don't add dead end nodes to the main node list
+                return WireSegment(
+                    wireType = wireType,
+                    startNode = startNode,
+                    endNode = deadEndNode,
+                    length = path.size,
+                    tilePositions = path.toList() + listOf(currentPos),
+                    decayConstant = decayConstant
+                )
+            }
+
+            path.add(currentPos)
+
+            // Find the exit direction (not the direction we came from)
+            val entryDir = direction.wireNodeMirror()
+            var exitDir: Int? = null
+
+            for (dir in DIRECTIONS) {
+                if (dir != entryDir && (cnx and dir) != 0) {
+                    // Check if target is connected back
+                    val nextOffset = DIRECTION_OFFSETS[dir] ?: continue
+                    val nextPos = Point2i(currentPos.x + nextOffset.x, currentPos.y + nextOffset.y)
+                    val nextCnx = world.getWireGraphOf(nextPos.x, nextPos.y, wireType) ?: 0
+
+                    if ((nextCnx and dir.wireNodeMirror()) != 0) {
+                        exitDir = dir
+                        break
+                    }
+                }
+            }
+
+            if (exitDir == null) {
+                // Dead end
+                return WireSegment(
+                    wireType = wireType,
+                    startNode = startNode,
+                    endNode = LogicalWireNode.JunctionNode(currentPos, wireType, 1),
+                    length = path.size - 1,
+                    tilePositions = path.toList(),
+                    decayConstant = decayConstant
+                )
+            }
+
+            // Move to next tile
+            val nextOffset = DIRECTION_OFFSETS[exitDir]!!
+            currentPos = Point2i(currentPos.x + nextOffset.x, currentPos.y + nextOffset.y)
+            direction = exitDir
+        }
+
+        return null  // Safety: exceeded max iterations
+    }
+
+    private fun hasWireAt(x: Int, y: Int, wireType: ItemID): Boolean {
+        val blockAddr = LandUtil.getBlockAddr(world, x, y)
+        return world.wirings[blockAddr]?.ws?.contains(wireType) == true
+    }
+
+    /**
+     * Rebuild graphs for all wire types present in the world.
+     */
+    fun rebuildAll() {
+        // Collect all wire types
+        val wireTypes = HashSet<ItemID>()
+        world.wirings.values.forEach { wiringNode ->
+            wireTypes.addAll(wiringNode.ws)
+        }
+
+        wireTypes.forEach { wireType ->
+            rebuild(wireType)
+        }
+    }
+}

src/net/torvald/terrarum/modulebasegame/WorldSimulator.kt

@@ -12,6 +12,8 @@ import net.torvald.terrarum.gameactors.Controllable
 import net.torvald.terrarum.gameitems.ItemID
 import net.torvald.terrarum.gameworld.GameWorld
 import net.torvald.terrarum.gameworld.GameWorld.Companion.FLUID
+import net.torvald.terrarum.gameworld.LogicalWireNode
+import net.torvald.terrarum.gameworld.WireSegment
 import net.torvald.terrarum.modulebasegame.TerrarumIngame.Companion.inUpdateRange
 import net.torvald.terrarum.modulebasegame.gameactors.*
 import net.torvald.terrarum.modulebasegame.gameitems.AxeCore
@@ -525,37 +527,155 @@ object WorldSimulator {
                 it.inUpdateRange(world) && it.wireEmitterTypes.isNotEmpty()
             }
 
+    // Keep for backwards compatibility - used by oldTraversedNodes cleanup
     private val wireSimMarked = HashSet<Long>()
     private val wireSimPoints = Queue<WireGraphCursor>()
     private val oldTraversedNodes = ArrayList<WireGraphCursor>()
     private val fixtureCache = HashMap<Point2i, Pair<Electric, WireEmissionType>>() // also instance of Electric
 
+    /**
+     * Simulates wire signal propagation using the two-layer logical wire graph.
+     *
+     * This implementation operates on logical nodes (fixtures, junctions) and segments
+     * rather than individual tiles, reducing complexity from O(wire_tiles) to O(logical_nodes).
+     *
+     * Signal strength is calculated per-segment and stored for parametric brightness evaluation.
+     * Per-tile emission states are also updated for backwards compatibility with existing code.
+     */
     private fun simulateWires(delta: Float) {
-        // unset old wires before we begin
+        // Clear old per-tile emission states for backwards compatibility
         oldTraversedNodes.forEach { (x, y, _, _, wire) ->
             world.getAllWiringGraph(x, y)?.get(wire)?.emt?.set(0.0, 0.0)
         }
-
         oldTraversedNodes.clear()
         fixtureCache.clear()
 
-        wiresimGetSourceBlocks().let { sources ->
-            // signal-emitting fixtures must set emitState of its own tiles via update()
-            sources.forEach {
-                it.wireEmitterTypes.forEach { (bbi, wireType) ->
-
-                    val startingPoint = it.worldBlockPos!! + it.blockBoxIndexToPoint2i(bbi)
-                    val signal = it.wireEmission[bbi] ?: Vector2(0.0, 0.0)
-
-                    world.getAllWiringGraph(startingPoint.x, startingPoint.y)?.keys?.filter { WireCodex[it].accepts == wireType }?.forEach { wire ->
-                        val simStartingPoint = WireGraphCursor(startingPoint, wire)
-                        wireSimMarked.clear()
-                        wireSimPoints.clear()
-                        traverseWireGraph(world, wire, simStartingPoint, signal, wireType)
+        // Collect all wire types that have active emitters
+        val activeWireTypes = HashSet<ItemID>()
+        wiresimGetSourceBlocks().forEach { fixture ->
+            fixture.wireEmitterTypes.forEach { (bbi, wireEmissionType) ->
+                val pos = fixture.worldBlockPos!! + fixture.blockBoxIndexToPoint2i(bbi)
+                world.getAllWiringGraph(pos.x, pos.y)?.keys?.forEach { wireType ->
+                    if (WireCodex[wireType].accepts == wireEmissionType) {
+                        activeWireTypes.add(wireType)
                     }
                 }
             }
         }
+
+        // Process each wire type
+        activeWireTypes.forEach { wireType ->
+            simulateWireType(wireType)
+        }
+    }
+
+    /**
+     * Simulate signal propagation for a specific wire type using the logical graph.
+     */
+    private fun simulateWireType(wireType: ItemID) {
+        val graph = world.logicalWireGraph.getGraph(wireType)
+
+        // Rebuild graph if it doesn't exist, is empty, or structure is dirty (fixtures added/removed)
+        if (graph == null || graph.nodes.isEmpty() || graph.structureDirty) {
+            world.logicalWireGraph.rebuild(wireType)
+        }
+
+        val currentGraph = world.logicalWireGraph.getGraph(wireType) ?: return
+        if (currentGraph.nodes.isEmpty()) return
+
+        val decayConstant = WireCodex.wireDecays[wireType] ?: 1.0
+        val emissionType = WireCodex[wireType].accepts
+
+        // Step 1: Reset all node signal strengths and segment strengths
+        currentGraph.nodes.forEach { node ->
+            node.signalStrength = Vector2(0.0, 0.0)
+        }
+        currentGraph.segments.forEach { segment ->
+            segment.startStrength = 0.0
+            segment.endStrength = 0.0
+        }
+
+        // Step 2: Get signals from emitter fixture nodes
+        val emitterNodes = currentGraph.nodes.filterIsInstance<LogicalWireNode.FixtureNode>()
+            .filter { it.isEmitter && it.fixtureRef.inUpdateRange(world) }
+
+        emitterNodes.forEach { emitterNode ->
+            val signal = emitterNode.fixtureRef.wireEmission[emitterNode.blockBoxIndex] ?: Vector2(0.0, 0.0)
+            emitterNode.signalStrength = signal.copy()
+        }
+
+        // Step 3: BFS propagation on logical graph
+        val visited = HashSet<LogicalWireNode>()
+        val queue = ArrayDeque<LogicalWireNode>()
+
+        // Start from all emitter nodes
+        emitterNodes.forEach { node ->
+            if (node.signalStrength.x > 0.0 || node.signalStrength.y > 0.0) {
+                queue.add(node)
+            }
+        }
+
+        while (queue.isNotEmpty()) {
+            val node = queue.removeFirst()
+            if (visited.contains(node)) continue
+            visited.add(node)
+
+            // Propagate through connected segments
+            node.connectedSegments.forEach { segment ->
+                val otherNode = segment.getOtherEnd(node)
+
+                // Calculate decayed signal at the other end
+                val decayedSignal = node.signalStrength.copy()
+                decayedSignal.x *= decayConstant.pow(segment.length.toDouble())
+                decayedSignal.y *= decayConstant.pow(segment.length.toDouble())
+
+                // Update segment strengths for brightness calculation
+                if (node === segment.startNode || node == segment.startNode) {
+                    segment.startStrength = maxOf(segment.startStrength, node.signalStrength.x)
+                } else {
+                    segment.endStrength = maxOf(segment.endStrength, node.signalStrength.x)
+                }
+
+                // Update other node with max signal (handles multiple paths)
+                if (decayedSignal.x > otherNode.signalStrength.x) {
+                    otherNode.signalStrength.x = decayedSignal.x
+                }
+                if (decayedSignal.y > otherNode.signalStrength.y) {
+                    otherNode.signalStrength.y = decayedSignal.y
+                }
+
+                // Add to queue for further propagation
+                if (!visited.contains(otherNode)) {
+                    queue.add(otherNode)
+                }
+            }
+        }
+
+        // Step 4: Update per-tile emission states for backwards compatibility
+        // This allows getWireEmitStateOf() to work alongside the new getWireBrightness()
+        currentGraph.segments.forEach { segment ->
+            segment.tilePositions.forEachIndexed { index, pos ->
+                val brightness = segment.getBrightnessAtOffset(index)
+                val emitState = Vector2(brightness, 0.0)
+                world.setWireEmitStateOf(pos.x, pos.y, wireType, emitState)
+
+                // Track for cleanup on next tick
+                oldTraversedNodes.add(WireGraphCursor(pos, wireType))
+            }
+        }
+
+        // Step 5: Notify sink fixtures
+        currentGraph.nodes.filterIsInstance<LogicalWireNode.FixtureNode>()
+            .filter { !it.isEmitter && it.fixtureRef.inUpdateRange(world) }
+            .forEach { sinkNode ->
+                if (sinkNode.signalStrength.x > 0.0 || sinkNode.signalStrength.y > 0.0) {
+                    val offsetX = sinkNode.blockBoxIndex % sinkNode.fixtureRef.blockBox.width
+                    val offsetY = sinkNode.blockBoxIndex / sinkNode.fixtureRef.blockBox.width
+                    sinkNode.fixtureRef.updateOnWireGraphTraversal(offsetX, offsetY, sinkNode.emissionType)
+                }
+            }
+
+        currentGraph.dirty = false
     }
 
     private fun calculateDecay(signal: Vector2, dist: Int, wire: ItemID, signalType: WireEmissionType): Vector2 {
@@ -563,7 +683,9 @@ object WorldSimulator {
         return signal * d.pow(dist.toDouble())
     }
 
-    private fun traverseWireGraph(world: GameWorld, wire: ItemID, startingPoint: WireGraphCursor, signal: Vector2, signalType: WireEmissionType) {
+    // Keep old traversal method for reference/fallback (can be removed later)
+    @Deprecated("Use simulateWireType() with logical graph instead")
+    private fun traverseWireGraphLegacy(world: GameWorld, wire: ItemID, startingPoint: WireGraphCursor, signal: Vector2, signalType: WireEmissionType) {
 
         val emissionType = WireCodex[wire].accepts
 

src/net/torvald/terrarum/modulebasegame/gameactors/Electric.kt

@@ -57,6 +57,30 @@ open class Electric : FixtureBase {
         const val ELECTRIC_EPSILON_GENERIC = 1.0 / 1024.0
     }
 
+    /**
+     * When an Electric fixture is spawned, mark all wire graphs as structurally dirty
+     * so they rebuild to include this fixture's emitter/sink nodes.
+     */
+    override fun onSpawn(tx: Int, ty: Int) {
+        super.onSpawn(tx, ty)
+        // Mark wire graphs as needing structural rebuild to include this fixture
+        if (wireEmitterTypes.isNotEmpty() || wireSinkTypes.isNotEmpty()) {
+            INGAME.world.logicalWireGraph.markAllStructureDirty()
+        }
+    }
+
+    /**
+     * When an Electric fixture is despawned, mark all wire graphs as structurally dirty
+     * so they rebuild without this fixture's nodes.
+     */
+    override fun despawn() {
+        // Mark wire graphs as needing structural rebuild before this fixture is removed
+        if (wireEmitterTypes.isNotEmpty() || wireSinkTypes.isNotEmpty()) {
+            INGAME.world.logicalWireGraph.markAllStructureDirty()
+        }
+        super.despawn()
+    }
+
     fun getWireEmitterAt(blockBoxIndex: BlockBoxIndex) = this.wireEmitterTypes[blockBoxIndex]
     fun getWireEmitterAt(point: Point2i) = this.wireEmitterTypes[pointToBlockBoxIndex(point)]
     fun getWireEmitterAt(x: Int, y: Int) = this.wireEmitterTypes[pointToBlockBoxIndex(x, y)]

src/net/torvald/terrarum/modulebasegame/gameitems/BlockBase.kt

@@ -236,6 +236,11 @@ object BlockBase {
         oldTileX = mtx
         oldTileY = mty
 
+        // Rebuild logical wire graph after connectivity is fully established
+        if (ret >= 0) {
+            ingame.world.logicalWireGraph.rebuild(itemID)
+        }
+
         ret
     }