bluebey-studio: 横から見たとき口が体を透ける問題を修正

正面判定を内積>0から>0.5に変更し、真横（内積がほぼ0）では深度テストを有効に戻すようにした。

1 files changed, 5 insertions, 2 deletions

diff --git a/public/bluebey-studio/src/main.js b/public/bluebey-studio/src/main.js
index 9178427..6507bf4 100644
--- a/public/bluebey-studio/src/main.js
+++ b/public/bluebey-studio/src/main.js
@@ -1428,8 +1428,11 @@ async function init() {
         && (mouth.tongue ?? 1) > 0.01;
       mouthMesh.getWorldDirection(mouthNormal);
       mouthMesh.getWorldPosition(mouthToCamera);
-      mouthToCamera.subVectors(view.camera.position, mouthToCamera);
-      const facing = mouthNormal.dot(mouthToCamera) > 0;
+      mouthToCamera.subVectors(view.camera.position, mouthToCamera).normalize();
+      // Only let the artwork win the depth test when the camera is actually in
+      // front of the face. At a side view the dot product is near zero, and the
+      // mouth must lose to the body (or it shows through the far side).
+      const facing = mouthNormal.dot(mouthToCamera) > 0.5;
       const wallOn = state.render.wall?.on === true || state.render.wall2?.on === true;
       const depthTest = !tongueOverLip || !facing || wallOn;
       if (mouthMesh.material.depthTest !== depthTest) {