From 80ae7f620ac4f3a00dc1411bc93123ec42d53c21 Mon Sep 17 00:00:00 2001
From: G30 <50341825+silentoplayz@users.noreply.github.com>
Date: Mon, 12 Oct 2026 15:32:27 -0400
Subject: [PATCH] fix: VRM 0.x voice avatars rest with their arms down (#32270)

---
 src/lib/utils/voice-avatar-renderer.ts | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/src/lib/utils/voice-avatar-renderer.ts b/src/lib/utils/voice-avatar-renderer.ts
index c91cd811e8..c245e39fb2 100644
--- a/src/lib/utils/voice-avatar-renderer.ts
+++ b/src/lib/utils/voice-avatar-renderer.ts
@@ -57,6 +57,7 @@ export async function createAvatarRenderer(
 	const camera = new THREE.PerspectiveCamera(30, 1, 0.01, 100);
 	const bone = (name: Parameters<typeof vrm.humanoid.getNormalizedBoneNode>[0]) =>
 		vrm.humanoid.getNormalizedBoneNode(name);
+	const mirror = vrm.meta.metaVersion === '0' ? -1 : 1;
 	const head = bone('head');
 	const spine = bone('spine');
 	const chest = bone('chest') ?? bone('upperChest');
@@ -82,7 +83,6 @@ export async function createAvatarRenderer(
 		];
 	});
 	// Start all built-in states from a relaxed, slightly asymmetric stance.
-	// Normalized VRM bones share T-pose axes across VRM 0 and 1.
 	const restingRotations: Partial<Record<Parameters<typeof bone>[0], [number, number, number]>> = {
 		hips: [0, 0, 0.025],
 		spine: [0.025, 0.015, -0.035],
@@ -104,7 +104,11 @@ export async function createAvatarRenderer(
 		rightFoot: [-0.045, -0.035, 0.025]
 	};
 	for (const [name, rotation] of Object.entries(restingRotations))
-		bone(name as Parameters<typeof bone>[0])?.rotation.set(...rotation);
+		bone(name as Parameters<typeof bone>[0])?.rotation.set(
+			rotation[0] * mirror,
+			rotation[1],
+			rotation[2] * mirror
+		);
 	// Resting fingers curl mainly at the first two joints, with a softer index finger.
 	for (const side of ['left', 'right'] as const) {
 		const sign = side === 'left' ? -1 : 1;
@@ -116,7 +120,7 @@ export async function createAvatarRenderer(
 				['Distal', 0.04]
 			] as const) {
 				const node = bone(`${side}${finger}${joint}`);
-				if (node) node.rotation.z = sign * amount;
+				if (node) node.rotation.z = sign * amount * mirror;
 			}
 		}
 	}
@@ -326,25 +330,26 @@ export async function createAvatarRenderer(
 			const breath = Math.sin(elapsed * 1.1) * 0.9 + Math.sin(elapsed * 0.47) * 0.1;
 			const sway = amount * (0.01 * Math.sin(elapsed * 0.43) + 0.003 * Math.sin(elapsed * 0.71));
 			if (spine) {
-				spine.rotation.x += amount * (0.006 * breath + 0.015 * listening);
+				spine.rotation.x += mirror * amount * (0.006 * breath + 0.015 * listening);
 				spine.rotation.y += amount * speaking * 0.008 * Math.sin(elapsed * 0.6);
-				spine.rotation.z += sway;
+				spine.rotation.z += mirror * sway;
 			}
 			if (chest) {
-				chest.rotation.x -= amount * 0.008 * breath;
-				chest.rotation.z -= sway * 0.35;
+				chest.rotation.x -= mirror * amount * 0.008 * breath;
+				chest.rotation.z -= mirror * sway * 0.35;
 			}
 			if (head) {
 				head.rotation.x +=
+					mirror *
 					amount *
 					(0.006 * breath + speaking * 0.012 * Math.sin(elapsed * 0.85) + listening * 0.025);
 				head.rotation.y +=
 					amount * (0.012 * Math.sin(elapsed * 0.32) + speaking * 0.008 * Math.sin(elapsed * 0.6));
 				head.rotation.z +=
-					amount * (0.006 * Math.sin(elapsed * 0.27) + listening * 0.025) - sway * 0.5;
+					mirror * (amount * (0.006 * Math.sin(elapsed * 0.27) + listening * 0.025) - sway * 0.5);
 			}
-			if (leftArm) leftArm.rotation.z += amount * 0.004 * breath;
-			if (rightArm) rightArm.rotation.z -= amount * 0.003 * Math.sin(elapsed * 1.1 - 0.2);
+			if (leftArm) leftArm.rotation.z += mirror * amount * 0.004 * breath;
+			if (rightArm) rightArm.rotation.z -= mirror * amount * 0.003 * Math.sin(elapsed * 1.1 - 0.2);
 			if (leftElbow) leftElbow.rotation.y -= amount * 0.006 * Math.sin(elapsed * 1.1 - 0.3);
 			if (rightElbow) rightElbow.rotation.y += amount * 0.004 * Math.sin(elapsed * 1.1 - 0.5);
 			if (current && (bodyWeight > 0 || authored)) {