From 2a583509abce99136aad852354a4d20ffa1002bb Mon Sep 17 00:00:00 2001
From: syuilo <4439005+syuilo@users.noreply.github.com>
Date: Sat, 4 Apr 2026 12:42:27 +0900
Subject: [PATCH] Update engine.ts

---
 packages/frontend/src/utility/room/engine.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/packages/frontend/src/utility/room/engine.ts b/packages/frontend/src/utility/room/engine.ts
index 3197d748a7..d1608b2e09 100644
--- a/packages/frontend/src/utility/room/engine.ts
+++ b/packages/frontend/src/utility/room/engine.ts
@@ -246,12 +246,16 @@ class ModelManager {
 			toMerge.push(newMesh);
 		}
 
-		const merged = BABYLON.Mesh.MergeMeshes(toMerge, true, true, undefined, false, true);
-
-		//merged.bakeCurrentTransformIntoVertices();
+		const groupedByMaterial = Object.groupBy(toMerge, m => m.material?.uniqueId ?? -1);
 
+		// 一度に(multiMultiMaterials: trueで)マージするよりも、いったん同じマテリアルを持つもの同士で(multiMultiMaterials: falseで)マージしてから、改めてそれらを(multiMultiMaterials: trueで)マージした方が(なぜか)ドローコールが減ってお得
+		const pre = [];
+		for (const group of Object.values(groupedByMaterial)) {
+			const merged = BABYLON.Mesh.MergeMeshes(group, true, true, undefined, false, false);
+			pre.push(merged);
+		}
+		const merged = BABYLON.Mesh.MergeMeshes(pre, true, true, undefined, false, true);
 		merged.parent = this.root;
-
 		this.bakedMeshes = [merged];
 
 		this.bakedCallback?.([...this.bakedMeshes, ...excludeMeshes]);