Move camera offset to consistent point in game loop

fixes #10027

src/client/camera.cpp

@@ -26,7 +26,8 @@
 #include <IGUIFont.h>
 #include <IVideoDriver.h>
 
-#define CAMERA_OFFSET_STEP 200
+static constexpr f32 CAMERA_OFFSET_STEP = 200;
+
 #define WIELDMESH_OFFSET_X 55.0f
 #define WIELDMESH_OFFSET_Y -35.0f
 #define WIELDMESH_AMPLITUDE_X 7.0f
@@ -281,6 +282,20 @@ void Camera::addArmInertia(f32 player_yaw)
 	}
 }
 
+void Camera::updateOffset()
+{
+	v3f cp = m_camera_position / BS;
+
+	// Update offset if too far away from the center of the map
+	m_camera_offset = v3s16(
+		floorf(cp.X / CAMERA_OFFSET_STEP) * CAMERA_OFFSET_STEP,
+		floorf(cp.Y / CAMERA_OFFSET_STEP) * CAMERA_OFFSET_STEP,
+		floorf(cp.Z / CAMERA_OFFSET_STEP) * CAMERA_OFFSET_STEP
+	);
+
+	// No need to update m_cameranode as that will be done before the next render.
+}
+
 void Camera::update(LocalPlayer* player, f32 frametime, f32 tool_reload_ratio)
 {
 	// Get player position
@@ -366,6 +381,7 @@ void Camera::update(LocalPlayer* player, f32 frametime, f32 tool_reload_ratio)
 		m_headnode->updateAbsolutePosition();
 	}
 
+
 	// Compute relative camera position and target
 	v3f rel_cam_pos = v3f(0,0,0);
 	v3f rel_cam_target = v3f(0,0,1);
@@ -397,12 +413,11 @@ void Camera::update(LocalPlayer* player, f32 frametime, f32 tool_reload_ratio)
 	v3f abs_cam_up = m_headnode->getAbsoluteTransformation()
 			.rotateAndScaleVect(rel_cam_up);
 
-	// Separate camera position for calculation
-	v3f my_cp = m_camera_position;
-
 	// Reposition the camera for third person view
 	if (m_camera_mode > CAMERA_MODE_FIRST)
 	{
+		v3f my_cp = m_camera_position;
+
 		if (m_camera_mode == CAMERA_MODE_THIRD_FRONT)
 			m_camera_direction *= -1;
 
@@ -434,27 +449,19 @@ void Camera::update(LocalPlayer* player, f32 frametime, f32 tool_reload_ratio)
 		// If node blocks camera position don't move y to heigh
 		if (abort && my_cp.Y > player_position.Y+BS*2)
 			my_cp.Y = player_position.Y+BS*2;
+
+		// update the camera position in third-person mode to render blocks behind player
+		// and correctly apply liquid post FX.
+		m_camera_position = my_cp;
 	}
 
-	// Update offset if too far away from the center of the map
-	m_camera_offset.X += CAMERA_OFFSET_STEP*
-			(((s16)(my_cp.X/BS) - m_camera_offset.X)/CAMERA_OFFSET_STEP);
-	m_camera_offset.Y += CAMERA_OFFSET_STEP*
-			(((s16)(my_cp.Y/BS) - m_camera_offset.Y)/CAMERA_OFFSET_STEP);
-	m_camera_offset.Z += CAMERA_OFFSET_STEP*
-			(((s16)(my_cp.Z/BS) - m_camera_offset.Z)/CAMERA_OFFSET_STEP);
-
 	// Set camera node transformation
-	m_cameranode->setPosition(my_cp-intToFloat(m_camera_offset, BS));
-	m_cameranode->updateAbsolutePosition();
+	m_cameranode->setPosition(m_camera_position - intToFloat(m_camera_offset, BS));
 	m_cameranode->setUpVector(abs_cam_up);
-	// *100.0 helps in large map coordinates
-	m_cameranode->setTarget(my_cp-intToFloat(m_camera_offset, BS) + 100 * m_camera_direction);
-
-	// update the camera position in third-person mode to render blocks behind player
-	// and correctly apply liquid post FX.
-	if (m_camera_mode != CAMERA_MODE_FIRST)
-		m_camera_position = my_cp;
+	m_cameranode->updateAbsolutePosition();
+	// *100 helps in large map coordinates
+	m_cameranode->setTarget(m_camera_position - intToFloat(m_camera_offset, BS)
+		+ 100 * m_camera_direction);
 
 	/*
 	 * Apply server-sent FOV, instantaneous or smooth transition.

src/client/camera.h

@@ -147,6 +147,9 @@ public:
 	// Update the camera from the local player's position.
 	void update(LocalPlayer* player, f32 frametime, f32 tool_reload_ratio);
 
+	// Adjust the camera offset when needed
+	void updateOffset();
+
 	// Update render distance
 	void updateViewingRange();
 

src/client/game.cpp

@@ -564,6 +564,7 @@ protected:
 	void updatePauseState();
 	void step(f32 dtime);
 	void processClientEvents(CameraOrientation *cam);
+	void updateCameraOffset();
 	void updateCamera(f32 dtime);
 	void updateSound(f32 dtime);
 	void processPlayerInteraction(f32 dtime, bool show_hud);
@@ -988,6 +989,12 @@ void Game::run()
 		m_game_ui->clearInfoText();
 
 		updateProfilers(stats, draw_times, dtime);
+
+		// Update camera offset once before doing anything.
+		// In contrast to other updates the latency of this doesn't matter,
+		// since it's invisible to the user. But it needs to be consistent.
+		updateCameraOffset();
+
 		processUserInput(dtime);
 		// Update camera before player movement to avoid camera lag of one frame
 		updateCameraDirection(&cam_view_target, dtime);
@@ -1005,6 +1012,7 @@ void Game::run()
 
 		processClientEvents(&cam_view_target);
 		updateDebugState();
+		// Update camera here so it is in-sync with CAO position
 		updateCamera(dtime);
 		updateSound(dtime);
 		processPlayerInteraction(dtime, m_game_ui->m_flags.show_hud);
@@ -2919,8 +2927,6 @@ void Game::updateCamera(f32 dtime)
 	ToolCapabilities playeritem_toolcap =
 		playeritem.getToolCapabilities(itemdef_manager);
 
-	v3s16 old_camera_offset = camera->getOffset();
-
 	if (wasKeyPressed(KeyType::CAMERA_MODE)) {
 		GenericCAO *playercao = player->getCAO();
 
@@ -2945,26 +2951,36 @@ void Game::updateCamera(f32 dtime)
 	camera->update(player, dtime, tool_reload_ratio);
 	camera->step(dtime);
 
-	f32 camera_fov = camera->getFovMax();
-	v3s16 camera_offset = camera->getOffset();
-
-	m_camera_offset_changed = (camera_offset != old_camera_offset);
-
 	if (!m_flags.disable_camera_update) {
-		v3f camera_position = camera->getPosition();
-		v3f camera_direction = camera->getDirection();
-
-		auto &env = client->getEnv();
-		env.getClientMap().updateCamera(camera_position,
-				camera_direction, camera_fov, camera_offset, player->light_color);
-
-		if (m_camera_offset_changed) {
-			env.updateCameraOffset(camera_offset);
-			clouds->updateCameraOffset(camera_offset);
-		}
+		client->getEnv().getClientMap().updateCamera(camera->getPosition(),
+			camera->getDirection(), camera->getFovMax(), camera->getOffset(),
+			player->light_color);
 	}
 }
 
+void Game::updateCameraOffset()
+{
+	ClientEnvironment &env = client->getEnv();
+
+	v3s16 old_camera_offset = camera->getOffset();
+
+	camera->updateOffset();
+
+	v3s16 camera_offset = camera->getOffset();
+
+	m_camera_offset_changed = camera_offset != old_camera_offset;
+	if (!m_camera_offset_changed)
+		return;
+
+	if (!m_flags.disable_camera_update) {
+		env.getClientMap().updateCamera(camera->getPosition(),
+			camera->getDirection(), camera->getFovMax(), camera_offset,
+			env.getLocalPlayer()->light_color);
+
+		env.updateCameraOffset(camera_offset);
+		clouds->updateCameraOffset(camera_offset);
+	}
+}
 
 void Game::updateSound(f32 dtime)
 {