Add First Person Attachments (#10360)

Fixes some other third person camera specific attachments.
Implements a single new flag for entities to be forced visible in first person mode.
Old mods do not need to be updated to use the new flag and are fully backwards compatible.

12 files changed, 101 insertions, 35 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index c21da1871..77fb4a654 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -6167,12 +6167,14 @@ object you are working with still exists.
   `frame_loop`.
 * `set_animation_frame_speed(frame_speed)`
     * `frame_speed`: number, default: `15.0`
-* `set_attach(parent, bone, position, rotation)`
+* `set_attach(parent, bone, position, rotation, forced_visible)`
     * `bone`: string
     * `position`: `{x=num, y=num, z=num}` (relative)
     * `rotation`: `{x=num, y=num, z=num}` = Rotation on each axis, in degrees
-* `get_attach()`: returns parent, bone, position, rotation or nil if it isn't
-  attached.
+    * `forced_visible`: Boolean to control whether the attached entity 
+       should appear in first person.
+* `get_attach()`: returns parent, bone, position, rotation, forced_visible, 
+    or nil if it isn't attached.
 * `set_detach()`
 * `set_bone_position(bone, position, rotation)`
     * `bone`: string
diff --git a/src/activeobject.h b/src/activeobject.h
index 85e160d10..0829858ad 100644
--- a/src/activeobject.h
+++ b/src/activeobject.h
@@ -120,9 +120,9 @@ public:
 
 
 	virtual void setAttachment(int parent_id, const std::string &bone, v3f position,
-			v3f rotation) {}
+			v3f rotation, bool force_visible) {}
 	virtual void getAttachment(int *parent_id, std::string *bone, v3f *position,
-			v3f *rotation) const {}
+			v3f *rotation, bool *force_visible) const {}
 	virtual void clearChildAttachments() {}
 	virtual void clearParentAttachment() {}
 	virtual void addAttachmentChild(int child_id) {}
diff --git a/src/client/content_cao.cpp b/src/client/content_cao.cpp
index c1715a289..fae06554a 100644
--- a/src/client/content_cao.cpp
+++ b/src/client/content_cao.cpp
@@ -456,7 +456,8 @@ void GenericCAO::setChildrenVisible(bool toset)
 	for (u16 cao_id : m_attachment_child_ids) {
 		GenericCAO *obj = m_env->getGenericCAO(cao_id);
 		if (obj) {
-			obj->setVisible(toset);
+			// Check if the entity is forced to appear in first person.
+			obj->setVisible(obj->isForcedVisible() ? true : toset);
 		}
 	}
 }
@@ -477,8 +478,6 @@ void GenericCAO::setAttachment(int parent_id, const std::string &bone, v3f posit
 		if (parent)
 			parent->addAttachmentChild(m_id);
 	}
-
-
 	updateAttachments();
 }
 
@@ -498,7 +497,7 @@ void GenericCAO::clearChildAttachments()
 		int child_id = *m_attachment_child_ids.begin();
 
 		if (ClientActiveObject *child = m_env->getActiveObject(child_id))
-			child->setAttachment(0, "", v3f(), v3f());
+			child->setAttachment(0, "", v3f(), v3f(), false);
 
 		removeAttachmentChild(child_id);
 	}
@@ -800,6 +799,7 @@ void GenericCAO::addToScene(ITextureSource *tsrc)
 	updateBonePosition();
 	updateAttachments();
 	setNodeLight(m_last_light);
+	updateMeshCulling();
 }
 
 void GenericCAO::updateLight(u32 day_night_ratio)
@@ -1411,6 +1411,9 @@ void GenericCAO::updateTextures(std::string mod)
 				setMeshColor(mesh, m_prop.colors[0]);
 		}
 	}
+	// Prevent showing the player after changing texture
+	if (m_is_local_player)
+		updateMeshCulling();
 }
 
 void GenericCAO::updateAnimation()
@@ -1739,12 +1742,25 @@ void GenericCAO::processMessage(const std::string &data)
 		std::string bone = deSerializeString16(is);
 		v3f position = readV3F32(is);
 		v3f rotation = readV3F32(is);
+		m_force_visible = readU8(is); // Returns false for EOF
 
 		setAttachment(parent_id, bone, position, rotation);
 
+		// Forcibly show attachments if required by set_attach
+		if (m_force_visible)
+			m_is_visible = true;
 		// localplayer itself can't be attached to localplayer
-		if (!m_is_local_player)
-			m_is_visible = !m_attached_to_local;
+		else if (!m_is_local_player) {
+			// Objects attached to the local player should be hidden in first
+			// person provided the forced boolean isn't set.
+			m_is_visible = !m_attached_to_local ||
+				m_client->getCamera()->getCameraMode() != CAMERA_MODE_FIRST;
+			m_force_visible = false;
+		} else {
+			// Local players need to have this set,
+			// otherwise first person attachments fail.
+			m_is_visible = true;
+		}
 	} else if (cmd == AO_CMD_PUNCHED) {
 		u16 result_hp = readU16(is);
 
@@ -1858,5 +1874,33 @@ std::string GenericCAO::debugInfoText()
 	return os.str();
 }
 
+void GenericCAO::updateMeshCulling()
+{
+	if (!m_is_local_player)
+		return;
+
+	// Grab the active player scene node so we know there's
+	// at least a mesh to occlude from the camera.
+	irr::scene::ISceneNode *node = getSceneNode();
+	if (!node)
+		return;
+
+	if (m_client->getCamera()->getCameraMode() == CAMERA_MODE_FIRST) {
+		// Hide the mesh by culling both front and
+		// back faces. Serious hackyness but it works for our
+		// purposes. This also preserves the skeletal armature.
+		node->setMaterialFlag(video::EMF_BACK_FACE_CULLING,
+			true);
+		node->setMaterialFlag(video::EMF_FRONT_FACE_CULLING,
+			true);
+	} else {
+		// Restore mesh visibility.
+		node->setMaterialFlag(video::EMF_BACK_FACE_CULLING,
+			m_prop.backface_culling);
+		node->setMaterialFlag(video::EMF_FRONT_FACE_CULLING,
+			false);
+	}
+}
+
 // Prototype
 GenericCAO proto_GenericCAO(NULL, NULL);
diff --git a/src/client/content_cao.h b/src/client/content_cao.h
index 974ff9a1e..daf697767 100644
--- a/src/client/content_cao.h
+++ b/src/client/content_cao.h
@@ -124,6 +124,7 @@ private:
 	float m_step_distance_counter = 0.0f;
 	u8 m_last_light = 255;
 	bool m_is_visible = false;
+	bool m_force_visible = false;
 	s8 m_glow = 0;
 	// Material
 	video::E_MATERIAL_TYPE m_material_type;
@@ -215,6 +216,11 @@ public:
 		m_is_visible = toset;
 	}
 
+	inline bool isForcedVisible() const
+	{
+		return m_force_visible;
+	}
+
 	void setChildrenVisible(bool toset);
 	void setAttachment(int parent_id, const std::string &bone, v3f position, v3f rotation);
 	void getAttachment(int *parent_id, std::string *bone, v3f *position,
@@ -275,4 +281,6 @@ public:
 	{
 		return m_prop.infotext;
 	}
+
+	void updateMeshCulling();
 };
diff --git a/src/client/game.cpp b/src/client/game.cpp
index 8f9d51417..366464467 100644
--- a/src/client/game.cpp
+++ b/src/client/game.cpp
@@ -2950,7 +2950,8 @@ void Game::updateCamera(u32 busy_time, f32 dtime)
 
 		camera->toggleCameraMode();
 
-		playercao->setVisible(camera->getCameraMode() > CAMERA_MODE_FIRST);
+		// Make the player visible depending on camera mode.
+		playercao->updateMeshCulling();
 		playercao->setChildrenVisible(camera->getCameraMode() > CAMERA_MODE_FIRST);
 	}
 
diff --git a/src/clientiface.cpp b/src/clientiface.cpp
index 602a44c90..28a0ee770 100644
--- a/src/clientiface.cpp
+++ b/src/clientiface.cpp
@@ -80,10 +80,11 @@ LuaEntitySAO *getAttachedObject(PlayerSAO *sao, ServerEnvironment *env)
 	int id;
 	std::string bone;
 	v3f dummy;
-	sao->getAttachment(&id, &bone, &dummy, &dummy);
+	bool force_visible;
+	sao->getAttachment(&id, &bone, &dummy, &dummy, &force_visible);
 	ServerActiveObject *ao = env->getActiveObject(id);
 	while (id && ao) {
-		ao->getAttachment(&id, &bone, &dummy, &dummy);
+		ao->getAttachment(&id, &bone, &dummy, &dummy, &force_visible);
 		if (id)
 			ao = env->getActiveObject(id);
 	}
diff --git a/src/script/lua_api/l_camera.cpp b/src/script/lua_api/l_camera.cpp
index bfa60be67..40251154c 100644
--- a/src/script/lua_api/l_camera.cpp
+++ b/src/script/lua_api/l_camera.cpp
@@ -63,7 +63,8 @@ int LuaCamera::l_set_camera_mode(lua_State *L)
 		return 0;
 
 	camera->setCameraMode((CameraMode)((int)lua_tonumber(L, 2)));
-	playercao->setVisible(camera->getCameraMode() > CAMERA_MODE_FIRST);
+	// Make the player visible depending on camera mode.
+	playercao->updateMeshCulling();
 	playercao->setChildrenVisible(camera->getCameraMode() > CAMERA_MODE_FIRST);
 	return 0;
 }
diff --git a/src/script/lua_api/l_object.cpp b/src/script/lua_api/l_object.cpp
index 303b1175b..fead4e849 100644
--- a/src/script/lua_api/l_object.cpp
+++ b/src/script/lua_api/l_object.cpp
@@ -664,7 +664,7 @@ int ObjectRef::l_get_bone_position(lua_State *L)
 	return 2;
 }
 
-// set_attach(self, parent, bone, position, rotation)
+// set_attach(self, parent, bone, position, rotation, force_visible)
 int ObjectRef::l_set_attach(lua_State *L)
 {
 	GET_ENV_PTR;
@@ -687,7 +687,8 @@ int ObjectRef::l_set_attach(lua_State *L)
 	std::string bone;
 	v3f position = v3f(0, 0, 0);
 	v3f rotation = v3f(0, 0, 0);
-	co->getAttachment(&parent_id, &bone, &position, &rotation);
+	bool force_visible;
+	co->getAttachment(&parent_id, &bone, &position, &rotation, &force_visible);
 	if (parent_id) {
 		ServerActiveObject *old_parent = env->getActiveObject(parent_id);
 		old_parent->removeAttachmentChild(co->getId());
@@ -702,7 +703,8 @@ int ObjectRef::l_set_attach(lua_State *L)
 	rotation = v3f(0, 0, 0);
 	if (!lua_isnil(L, 5))
 		rotation = read_v3f(L, 5);
-	co->setAttachment(parent->getId(), bone, position, rotation);
+	force_visible = readParam<bool>(L, 6, false);
+	co->setAttachment(parent->getId(), bone, position, rotation, force_visible);
 	parent->addAttachmentChild(co->getId());
 	return 0;
 }
@@ -722,7 +724,8 @@ int ObjectRef::l_get_attach(lua_State *L)
 	std::string bone;
 	v3f position = v3f(0, 0, 0);
 	v3f rotation = v3f(0, 0, 0);
-	co->getAttachment(&parent_id, &bone, &position, &rotation);
+	bool force_visible;
+	co->getAttachment(&parent_id, &bone, &position, &rotation, &force_visible);
 	if (!parent_id)
 		return 0;
 	ServerActiveObject *parent = env->getActiveObject(parent_id);
@@ -731,7 +734,8 @@ int ObjectRef::l_get_attach(lua_State *L)
 	lua_pushlstring(L, bone.c_str(), bone.size());
 	push_v3f(L, position);
 	push_v3f(L, rotation);
-	return 4;
+	lua_pushboolean(L, force_visible);
+	return 5;
 }
 
 // set_detach(self)
diff --git a/src/server/luaentity_sao.cpp b/src/server/luaentity_sao.cpp
index f20914f7f..b39797531 100644
--- a/src/server/luaentity_sao.cpp
+++ b/src/server/luaentity_sao.cpp
@@ -238,9 +238,9 @@ std::string LuaEntitySAO::getClientInitializationData(u16 protocol_version)
 	msg_os << serializeString32(generateUpdateAnimationCommand()); // 3
 	for (const auto &bone_pos : m_bone_position) {
 		msg_os << serializeString32(generateUpdateBonePositionCommand(
-			bone_pos.first, bone_pos.second.X, bone_pos.second.Y)); // m_bone_position.size
+			bone_pos.first, bone_pos.second.X, bone_pos.second.Y)); // 3 + N
 	}
-	msg_os << serializeString32(generateUpdateAttachmentCommand()); // 4
+	msg_os << serializeString32(generateUpdateAttachmentCommand()); // 4 + m_bone_position.size
 
 	int message_count = 4 + m_bone_position.size();
 
diff --git a/src/server/player_sao.cpp b/src/server/player_sao.cpp
index 8d4938c3c..344d18a20 100644
--- a/src/server/player_sao.cpp
+++ b/src/server/player_sao.cpp
@@ -122,10 +122,10 @@ std::string PlayerSAO::getClientInitializationData(u16 protocol_version)
 	msg_os << serializeString32(generateUpdateAnimationCommand()); // 3
 	for (const auto &bone_pos : m_bone_position) {
 		msg_os << serializeString32(generateUpdateBonePositionCommand(
-			bone_pos.first, bone_pos.second.X, bone_pos.second.Y)); // m_bone_position.size
+			bone_pos.first, bone_pos.second.X, bone_pos.second.Y)); // 3 + N
 	}
-	msg_os << serializeString32(generateUpdateAttachmentCommand()); // 4
-	msg_os << serializeString32(generateUpdatePhysicsOverrideCommand()); // 5
+	msg_os << serializeString32(generateUpdateAttachmentCommand()); // 4 + m_bone_position.size
+	msg_os << serializeString32(generateUpdatePhysicsOverrideCommand()); // 5 + m_bone_position.size
 
 	int message_count = 5 + m_bone_position.size();
 
@@ -569,7 +569,8 @@ bool PlayerSAO::checkMovementCheat()
 			int parent_id;
 			std::string bone;
 			v3f attachment_rot;
-			getAttachment(&parent_id, &bone, &attachment_pos, &attachment_rot);
+			bool force_visible;
+			getAttachment(&parent_id, &bone, &attachment_pos, &attachment_rot, &force_visible);
 		}
 
 		v3f parent_pos = parent->getBasePosition();
diff --git a/src/server/unit_sao.cpp b/src/server/unit_sao.cpp
index d906e885e..2371640ca 100644
--- a/src/server/unit_sao.cpp
+++ b/src/server/unit_sao.cpp
@@ -121,8 +121,8 @@ void UnitSAO::sendOutdatedData()
 }
 // clang-format on
 
-void UnitSAO::setAttachment(
-		int parent_id, const std::string &bone, v3f position, v3f rotation)
+void UnitSAO::setAttachment(int parent_id, const std::string &bone, v3f position,
+		v3f rotation, bool force_visible)
 {
 	// Attachments need to be handled on both the server and client.
 	// If we just attach on the server, we can only copy the position of the parent.
@@ -137,6 +137,7 @@ void UnitSAO::setAttachment(
 	m_attachment_bone = bone;
 	m_attachment_position = position;
 	m_attachment_rotation = rotation;
+	m_force_visible = force_visible;
 	m_attachment_sent = false;
 
 	if (parent_id != old_parent) {
@@ -145,13 +146,14 @@ void UnitSAO::setAttachment(
 	}
 }
 
-void UnitSAO::getAttachment(
-		int *parent_id, std::string *bone, v3f *position, v3f *rotation) const
+void UnitSAO::getAttachment(int *parent_id, std::string *bone, v3f *position,
+		v3f *rotation, bool *force_visible) const
 {
 	*parent_id = m_attachment_parent_id;
 	*bone = m_attachment_bone;
 	*position = m_attachment_position;
 	*rotation = m_attachment_rotation;
+	*force_visible = m_force_visible;
 }
 
 void UnitSAO::clearChildAttachments()
@@ -159,7 +161,7 @@ void UnitSAO::clearChildAttachments()
 	for (int child_id : m_attachment_child_ids) {
 		// Child can be NULL if it was deleted earlier
 		if (ServerActiveObject *child = m_env->getActiveObject(child_id))
-			child->setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
+			child->setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0), false);
 	}
 	m_attachment_child_ids.clear();
 }
@@ -169,9 +171,9 @@ void UnitSAO::clearParentAttachment()
 	ServerActiveObject *parent = nullptr;
 	if (m_attachment_parent_id) {
 		parent = m_env->getActiveObject(m_attachment_parent_id);
-		setAttachment(0, "", m_attachment_position, m_attachment_rotation);
+		setAttachment(0, "", m_attachment_position, m_attachment_rotation, false);
 	} else {
-		setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
+		setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0), false);
 	}
 	// Do it
 	if (parent)
@@ -245,6 +247,7 @@ std::string UnitSAO::generateUpdateAttachmentCommand() const
 	os << serializeString16(m_attachment_bone);
 	writeV3F32(os, m_attachment_position);
 	writeV3F32(os, m_attachment_rotation);
+	writeU8(os, m_force_visible);
 	return os.str();
 }
 
diff --git a/src/server/unit_sao.h b/src/server/unit_sao.h
index 3cb7f0ad5..a21e055c5 100644
--- a/src/server/unit_sao.h
+++ b/src/server/unit_sao.h
@@ -64,9 +64,9 @@ public:
 	ServerActiveObject *getParent() const;
 	inline bool isAttached() const { return getParent(); }
 	void setAttachment(int parent_id, const std::string &bone, v3f position,
-			v3f rotation);
+			v3f rotation, bool force_visible);
 	void getAttachment(int *parent_id, std::string *bone, v3f *position,
-			v3f *rotation) const;
+			v3f *rotation, bool *force_visible) const;
 	void clearChildAttachments();
 	void clearParentAttachment();
 	void addAttachmentChild(int child_id);
@@ -133,4 +133,5 @@ private:
 	v3f m_attachment_position;
 	v3f m_attachment_rotation;
 	bool m_attachment_sent = false;
+	bool m_force_visible = false;
 };