From e680d7118ea69807d8daed083c84f46162706b48 Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Wed, 13 May 2026 13:21:29 +0200
Subject: [PATCH] Integrate spline corridor junction support for terrain
 patching and scene building

---
 .../apply-spline-road-to-terrain-command.ts   | 60 ++++++++++++++++---
 src/runtime-three/runtime-scene-build.ts      |  5 ++
 2 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/src/commands/apply-spline-road-to-terrain-command.ts b/src/commands/apply-spline-road-to-terrain-command.ts
index 4ecef571..d1a98bd1 100644
--- a/src/commands/apply-spline-road-to-terrain-command.ts
+++ b/src/commands/apply-spline-road-to-terrain-command.ts
@@ -7,7 +7,11 @@ import {
   getTerrains,
   type Terrain
 } from "../document/terrains";
-import { createSplineRoadTerrainPatch } from "../geometry/spline-road-terrain";
+import {
+  createSplineCorridorJunctionTerrainPatch,
+  createSplineRoadTerrainPatch
+} from "../geometry/spline-road-terrain";
+import { getSplineCorridorJunctionsConnectedToPath } from "../spline-corridor/spline-corridor-junctions";
 
 import {
   applyTerrainBrushPatchToDocument,
@@ -71,10 +75,26 @@ function createAppliedTerrainRoads(
     }
 
     const before = cloneTerrain(terrain);
-    const terrainWithMaterialLayer =
+    let terrainWithMaterialLayer =
       path.road.materialId === null
         ? terrain
         : ensureTerrainMaterialLayer(terrain, path.road.materialId).terrain;
+    const connectedJunctions = getSplineCorridorJunctionsConnectedToPath({
+      junctions: document.splineCorridorJunctions,
+      pathId
+    }).filter((junction) => junction.enabled);
+
+    for (const junction of connectedJunctions) {
+      if (junction.materialId === null) {
+        continue;
+      }
+
+      terrainWithMaterialLayer = ensureTerrainMaterialLayer(
+        terrainWithMaterialLayer,
+        junction.materialId
+      ).terrain;
+    }
+
     let tempDocument = {
       ...document,
       terrains: {
@@ -82,20 +102,44 @@ function createAppliedTerrainRoads(
         [terrain.id]: cloneTerrain(terrainWithMaterialLayer)
       }
     };
+    let changed = false;
     const patch = createSplineRoadTerrainPatch({
       path,
       terrain: tempDocument.terrains[terrain.id]!
     });
 
-    if (patch === null || isTerrainBrushPatchEmpty(patch)) {
+    if (patch !== null && !isTerrainBrushPatchEmpty(patch)) {
+      tempDocument = applyTerrainBrushPatchToDocument(
+        tempDocument,
+        patch,
+        "forward"
+      );
+      changed = true;
+    }
+
+    for (const junction of connectedJunctions) {
+      const junctionPatch = createSplineCorridorJunctionTerrainPatch({
+        junction,
+        paths: Object.values(document.paths),
+        terrain: tempDocument.terrains[terrain.id]!
+      });
+
+      if (junctionPatch === null || isTerrainBrushPatchEmpty(junctionPatch)) {
+        continue;
+      }
+
+      tempDocument = applyTerrainBrushPatchToDocument(
+        tempDocument,
+        junctionPatch,
+        "forward"
+      );
+      changed = true;
+    }
+
+    if (!changed) {
       continue;
     }
 
-    tempDocument = applyTerrainBrushPatchToDocument(
-      tempDocument,
-      patch,
-      "forward"
-    );
     appliedTerrains.push({
       terrainId: terrain.id,
       before,
diff --git a/src/runtime-three/runtime-scene-build.ts b/src/runtime-three/runtime-scene-build.ts
index 7bd4063c..705cce9e 100644
--- a/src/runtime-three/runtime-scene-build.ts
+++ b/src/runtime-three/runtime-scene-build.ts
@@ -67,6 +67,10 @@ import {
   type ScenePathRoadSettings,
   type ScenePathPoint
 } from "../document/paths";
+import {
+  getSplineCorridorJunctions,
+  type SplineCorridorJunction
+} from "../document/spline-corridor-junctions";
 import {
   cloneTerrain,
   createEmptyTerrainFoliageBlockerMask,
@@ -86,6 +90,7 @@ import {
   deriveSplineCorridorBoxColliders,
   type SplineCorridorBoxCollider
 } from "../spline-corridor/spline-corridor-colliders";
+import { resolveSplineCorridorJunctionClipIntervals } from "../spline-corridor/spline-corridor-junctions";
 import {
   cloneWorldSettings,
   type WorldSettings