Fix taxi mount orientation and eliminate tile loading hitches

Fixes two critical taxi flight issues:

1. Mount orientation now correctly faces flight direction:
   - Prevent camera controller from updating facingYaw during taxi (externalFollow_ check)
   - Taxi orientation callback system updates mount rotation from spline tangent
   - Initial orientation set when flight starts
   - Smooth Catmull-Rom spline interpolation for natural curved paths

2. Eliminate frame hitches from tile loading during flight:
   - New taxiFlightStartCallback uploads ALL precached tiles to GPU before flight begins
   - Previously tiles loaded async during 3s mount delay but uploaded 1/frame during flight
   - Now processAllReadyTiles() blocks briefly after mount delay to batch upload everything
   - Combined with 2.0s terrain update interval and aggressive culling for smooth flight

Additional optimizations:
   - Aggressive taxi culling: skip models <15 units, all foliage/trees, underwater objects
   - Max render distance reduced to 150 units during taxi
   - Movement heartbeat packets disabled during taxi (server controls position)
   - Reduced taxi speed from 32 to 18 units/sec to prevent streaming overload

include/game/game_handler.hpp

@@ -501,6 +501,14 @@ public:
     using TaxiPrecacheCallback = std::function<void(const std::vector<glm::vec3>&)>;
     void setTaxiPrecacheCallback(TaxiPrecacheCallback cb) { taxiPrecacheCallback_ = std::move(cb); }
 
+    // Taxi orientation callback (for mount rotation)
+    using TaxiOrientationCallback = std::function<void(float orientationRadians)>;
+    void setTaxiOrientationCallback(TaxiOrientationCallback cb) { taxiOrientationCallback_ = std::move(cb); }
+
+    // Callback for when taxi flight is about to start (after mounting delay, before movement begins)
+    using TaxiFlightStartCallback = std::function<void()>;
+    void setTaxiFlightStartCallback(TaxiFlightStartCallback cb) { taxiFlightStartCallback_ = std::move(cb); }
+
     bool isMounted() const { return currentMountDisplayId_ != 0; }
     bool isHostileAttacker(uint64_t guid) const { return hostileAttackers_.count(guid) > 0; }
     float getServerRunSpeed() const { return serverRunSpeed_; }
@@ -959,7 +967,7 @@ private:
     bool taxiClientActive_ = false;
     size_t taxiClientIndex_ = 0;
     std::vector<glm::vec3> taxiClientPath_;
-    float taxiClientSpeed_ = 32.0f;
+    float taxiClientSpeed_ = 18.0f;  // Reduced from 32 to prevent loading hitches
     float taxiClientSegmentProgress_ = 0.0f;
     bool taxiMountingDelay_ = false;  // Delay before flight starts (terrain precache time)
     float taxiMountingTimer_ = 0.0f;
@@ -1023,6 +1031,8 @@ private:
     NpcSwingCallback npcSwingCallback_;
     MountCallback mountCallback_;
     TaxiPrecacheCallback taxiPrecacheCallback_;
+    TaxiOrientationCallback taxiOrientationCallback_;
+    TaxiFlightStartCallback taxiFlightStartCallback_;
     uint32_t currentMountDisplayId_ = 0;
     float serverRunSpeed_ = 7.0f;
     bool playerDead_ = false;

include/rendering/camera_controller.hpp

@@ -89,6 +89,7 @@ public:
     void setMountHeightOffset(float offset) { mountHeightOffset_ = offset; }
     void setExternalFollow(bool enabled) { externalFollow_ = enabled; }
     void setExternalMoving(bool moving) { externalMoving_ = moving; }
+    void setFacingYaw(float yaw) { facingYaw = yaw; }  // For taxi/scripted movement
     void clearMovementInputs();
 
     // For first-person player hiding

src/core/application.cpp

@@ -420,10 +420,9 @@ void Application::update(float deltaTime) {
             }
             if (renderer && renderer->getTerrainManager()) {
                 renderer->getTerrainManager()->setStreamingEnabled(true);
-                // With 8GB tile cache, keep streaming active during taxi at moderate rate.
-                // Increase load radius to pre-cache tiles ahead of flight path.
+                // With 8GB tile cache and precaching, minimize streaming during taxi
                 if (onTaxi) {
-                    renderer->getTerrainManager()->setUpdateInterval(0.3f);
+                    renderer->getTerrainManager()->setUpdateInterval(2.0f);  // Very infrequent updates - already precached
                     renderer->getTerrainManager()->setLoadRadius(2);  // 5x5 grid for taxi (each tile ~533 yards)
                 } else {
                     // Ramp streaming back in after taxi to avoid end-of-flight hitches.
@@ -466,7 +465,8 @@ void Application::update(float deltaTime) {
             }
 
             // Send movement heartbeat every 500ms (keeps server position in sync)
-            if (gameHandler && renderer) {
+            // Skip during taxi flights - server controls position
+            if (gameHandler && renderer && !onTaxi) {
                 movementHeartbeatTimer += deltaTime;
                 if (movementHeartbeatTimer >= 0.5f) {
                     movementHeartbeatTimer = 0.0f;
@@ -718,6 +718,23 @@ void Application::setupUICallbacks() {
         renderer->getTerrainManager()->precacheTiles(tilesToLoad);
     });
 
+    // Taxi orientation callback - update mount rotation during flight
+    gameHandler->setTaxiOrientationCallback([this](float orientationRadians) {
+        if (renderer && renderer->getCameraController()) {
+            // Convert radians to degrees for camera controller
+            float yawDegrees = glm::degrees(orientationRadians);
+            renderer->getCameraController()->setFacingYaw(yawDegrees);
+        }
+    });
+
+    // Taxi flight start callback - upload all precached tiles to GPU before flight begins
+    gameHandler->setTaxiFlightStartCallback([this]() {
+        if (renderer && renderer->getTerrainManager()) {
+            LOG_INFO("Uploading all precached tiles to GPU before taxi flight...");
+            renderer->getTerrainManager()->processAllReadyTiles();
+        }
+    });
+
     // Creature move callback (online mode) - update creature positions
     gameHandler->setCreatureMoveCallback([this](uint64_t guid, float x, float y, float z, uint32_t durationMs) {
         auto it = creatureInstances_.find(guid);

src/game/game_handler.cpp

@@ -269,6 +269,10 @@ void GameHandler::update(float deltaTime) {
             if (taxiMountingTimer_ >= 3.0f) {
                 taxiMountingDelay_ = false;
                 taxiMountingTimer_ = 0.0f;
+                // Upload all precached tiles to GPU before flight starts
+                if (taxiFlightStartCallback_) {
+                    taxiFlightStartCallback_();
+                }
                 if (!taxiPendingPath_.empty()) {
                     startClientTaxiPath(taxiPendingPath_);
                     taxiPendingPath_.clear();
@@ -5182,6 +5186,24 @@ void GameHandler::startClientTaxiPath(const std::vector<uint32_t>& pathNodes) {
         return;
     }
 
+    // Set initial orientation to face the first flight segment
+    if (!entityManager.hasEntity(playerGuid)) return;
+    auto playerEntity = entityManager.getEntity(playerGuid);
+    if (playerEntity) {
+        glm::vec3 start = taxiClientPath_[0];
+        glm::vec3 end = taxiClientPath_[1];
+        glm::vec3 dir = end - start;
+        float initialOrientation = std::atan2(dir.y, dir.x) - 1.57079632679f;
+
+        playerEntity->setPosition(start.x, start.y, start.z, initialOrientation);
+        movementInfo.orientation = initialOrientation;
+
+        // Update mount rotation immediately
+        if (taxiOrientationCallback_) {
+            taxiOrientationCallback_(initialOrientation);
+        }
+    }
+
     LOG_INFO("Taxi flight started with ", taxiClientPath_.size(), " spline waypoints");
     taxiClientActive_ = true;
 }
@@ -5234,20 +5256,52 @@ void GameHandler::updateClientTaxi(float deltaTime) {
         return;
     }
 
-    glm::vec3 dirNorm = dir / segmentLen;
-    glm::vec3 nextPos = start + dirNorm * (t * segmentLen);
+    // Use Catmull-Rom spline for smooth interpolation between waypoints
+    // Get surrounding points for spline curve
+    glm::vec3 p0 = (taxiClientIndex_ > 0) ? taxiClientPath_[taxiClientIndex_ - 1] : start;
+    glm::vec3 p1 = start;
+    glm::vec3 p2 = end;
+    glm::vec3 p3 = (taxiClientIndex_ + 2 < taxiClientPath_.size()) ?
+                   taxiClientPath_[taxiClientIndex_ + 2] : end;
 
-    // Add a flight arc to avoid terrain collisions.
-    float arcHeight = std::clamp(segmentLen * 0.15f, 20.0f, 120.0f);
-    float arc = 4.0f * t * (1.0f - t);
-    nextPos.z = glm::mix(start.z, end.z, t) + arcHeight * arc;
+    // Catmull-Rom spline formula for smooth curves
+    float t2 = t * t;
+    float t3 = t2 * t;
+    glm::vec3 nextPos = 0.5f * (
+        (2.0f * p1) +
+        (-p0 + p2) * t +
+        (2.0f * p0 - 5.0f * p1 + 4.0f * p2 - p3) * t2 +
+        (-p0 + 3.0f * p1 - 3.0f * p2 + p3) * t3
+    );
 
-    float orientation = std::atan2(dir.y, dir.x) - 1.57079632679f;
-    playerEntity->setPosition(nextPos.x, nextPos.y, nextPos.z, orientation);
+    // Calculate smooth direction for orientation (tangent to spline)
+    glm::vec3 tangent = 0.5f * (
+        (-p0 + p2) +
+        2.0f * (2.0f * p0 - 5.0f * p1 + 4.0f * p2 - p3) * t +
+        3.0f * (-p0 + 3.0f * p1 - 3.0f * p2 + p3) * t2
+    );
+
+    // Smooth orientation based on spline tangent
+    float targetOrientation = std::atan2(tangent.y, tangent.x) - 1.57079632679f;
+
+    // Smooth rotation transition (lerp towards target)
+    float currentOrientation = movementInfo.orientation;
+    float orientDiff = targetOrientation - currentOrientation;
+    // Normalize angle difference to [-PI, PI]
+    while (orientDiff > 3.14159265f) orientDiff -= 6.28318530f;
+    while (orientDiff < -3.14159265f) orientDiff += 6.28318530f;
+    float smoothOrientation = currentOrientation + orientDiff * std::min(1.0f, deltaTime * 3.0f);
+
+    playerEntity->setPosition(nextPos.x, nextPos.y, nextPos.z, smoothOrientation);
     movementInfo.x = nextPos.x;
     movementInfo.y = nextPos.y;
     movementInfo.z = nextPos.z;
-    movementInfo.orientation = orientation;
+    movementInfo.orientation = smoothOrientation;
+
+    // Update mount rotation to face flight direction
+    if (taxiOrientationCallback_) {
+        taxiOrientationCallback_(smoothOrientation);
+    }
 }
 
 void GameHandler::handleActivateTaxiReply(network::Packet& packet) {

src/rendering/camera_controller.cpp

@@ -224,7 +224,8 @@ void CameraController::update(float deltaTime) {
     // Get camera axes — project forward onto XY plane for walking
     glm::vec3 forward3D = camera->getForward();
     bool cameraDrivesFacing = rightMouseDown || mouseAutorun;
-    if (cameraDrivesFacing) {
+    // During taxi flights, orientation is controlled by the flight path, not player input
+    if (cameraDrivesFacing && !externalFollow_) {
         facingYaw = yaw;
     }
     float moveYaw = cameraDrivesFacing ? yaw : facingYaw;

src/rendering/m2_renderer.cpp

@@ -1644,7 +1644,8 @@ void M2Renderer::render(const Camera& camera, const glm::mat4& view, const glm::
     lastDrawCallCount = 0;
 
     // Adaptive render distance: keep longer tree/foliage visibility to reduce pop-in.
-    const float maxRenderDistance = (instances.size() > 600) ? 320.0f : 2800.0f;
+    // During taxi, use very short render distance to prevent loading hitches
+    const float maxRenderDistance = onTaxi_ ? 150.0f : (instances.size() > 600) ? 320.0f : 2800.0f;
     const float maxRenderDistanceSq = maxRenderDistance * maxRenderDistance;
     const float fadeStartFraction = 0.75f;
     const glm::vec3 camPos = camera.getPosition();
@@ -1713,10 +1714,20 @@ void M2Renderer::render(const Camera& camera, const glm::mat4& view, const glm::
 
         const M2ModelGPU& model = *currentModel;
 
-        // Skip small models when on taxi (performance optimization)
-        // Small props/foliage aren't visible from flight altitude anyway
-        if (onTaxi_ && model.boundRadius < 3.0f) {
-            continue;
+        // Aggressive culling during taxi for smooth flight
+        if (onTaxi_) {
+            // Skip all small/medium models (props, foliage, decorations)
+            if (model.boundRadius < 15.0f) {
+                continue;
+            }
+            // Skip all foliage and trees (even large ones cause hitching during load)
+            if (model.collisionNoBlock || model.collisionTreeTrunk) {
+                continue;
+            }
+            // Skip underwater objects (water is opaque from altitude)
+            if (instance.position.z < -5.0f) {
+                continue;
+            }
         }
 
         // Distance-based fade alpha for smooth pop-in (squared-distance, no sqrt)

src/rendering/renderer.cpp

@@ -1119,7 +1119,11 @@ void Renderer::update(float deltaTime) {
         }
 
         // Movement-facing comes from camera controller and is decoupled from LMB orbit.
-        if (cameraController->isMoving() || cameraController->isRightMouseHeld()) {
+        // During taxi flights, orientation is controlled by the flight path (not player input)
+        if (taxiFlight_) {
+            // Taxi flight: use orientation from flight path
+            characterYaw = cameraController->getFacingYaw();
+        } else if (cameraController->isMoving() || cameraController->isRightMouseHeld()) {
             characterYaw = cameraController->getFacingYaw();
         } else if (inCombat_ && targetPosition && !emoteActive && !isMounted()) {
             // Face target when in combat and idle