Near perfect match of unarmed head yaw compared to vanilla

src/xrGame/ActorAnimation.cpp

@@ -30,6 +30,7 @@ static const float p_spin0_factor = 0.0f;
 static const float p_spin1_factor = 0.2f;
 static const float p_shoulder_factor = 0.7f;
 static const float p_head_factor = 0.1f;
+static const float p_head_unarmed_factor = 0.1f;
 static const float r_spin0_factor = 0.3f;
 static const float r_spin1_factor = 0.3f;
 static const float r_shoulder_factor = 0.2f;
@@ -80,13 +81,15 @@ void CActor::Spine2Callback(CBoneInstance* B)
     B->mTransform.mulA_43(spin);
     B->mTransform.c = c;
 }
+extern Fvector g_first_person_cam_offset;
 void CActor::HeadCallback(CBoneInstance* B)
 {
     CActor* A = static_cast<CActor*>(B->callback_param());
     VERIFY(A);
     Fmatrix spin;
     float bone_yaw = angle_normalize_signed(A->r_torso.yaw - A->r_model_yaw - A->r_model_yaw_delta) * y_head_factor;
-    float bone_pitch = angle_normalize_signed(A->r_torso.pitch) * p_head_factor;
+    float correctedHeadFactor = A->inventory().GetActiveSlot() == NO_ACTIVE_SLOT ? p_head_unarmed_factor : p_head_factor;
+    float bone_pitch = angle_normalize_signed(A->cam_Active()->GetWorldPitch()) * correctedHeadFactor;
     float bone_roll = angle_normalize_signed(A->r_torso.roll) * r_head_factor;
     Fvector c = B->mTransform.c;
     spin.setXYZ(-bone_pitch, bone_yaw, bone_roll);