Smooth battle zone camera transitions

game/src/scene/whitebox_scene.cpp

@@ -6,6 +6,7 @@
 #include <frostbite2D/event/key_event.h>
 #include <frostbite2D/graphics/camera.h>
 #include <frostbite2D/graphics/renderer.h>
+#include <algorithm>
 
 namespace ns_game {
 
@@ -26,6 +27,7 @@ void WhiteboxScene::onEnter() {
 void WhiteboxScene::Update(float deltaTime) {
   frostbite2D::Scene::Update(deltaTime);
   updateBattleZones();
+  updateCameraBoundsBlend(deltaTime);
   updateCamera(deltaTime);
 }
 
@@ -93,6 +95,7 @@ void WhiteboxScene::configureCamera() {
   config.viewportWidth = static_cast<float>(config::kVirtualWidth);
   config.viewportHeight = static_cast<float>(config::kVirtualHeight);
   cameraController_.Configure(config);
+  currentCameraBounds_ = level_.cameraBounds;
 
   if (player_) {
     cameraController_.SnapToTarget(*camera, player_->GetWorldBounds());
@@ -111,6 +114,14 @@ void WhiteboxScene::toggleDebugOverlay() {
   debugFlags_.showSpawnPoints = enabled;
 }
 
+void WhiteboxScene::beginCameraBoundsBlend(
+    const frostbite2D::Rect& targetBounds) {
+  cameraBoundsBlendStart_ = currentCameraBounds_;
+  cameraBoundsBlendTarget_ = targetBounds;
+  cameraBoundsBlendTimer_ = 0.0f;
+  cameraBoundsBlendActive_ = true;
+}
+
 void WhiteboxScene::clearActiveBattleZone() {
   if (activeBattleZoneIndex_ < 0 ||
       activeBattleZoneIndex_ >= static_cast<int>(battleZoneStates_.size())) {
@@ -119,7 +130,34 @@ void WhiteboxScene::clearActiveBattleZone() {
 
   battleZoneStates_[static_cast<size_t>(activeBattleZoneIndex_)].cleared = true;
   activeBattleZoneIndex_ = -1;
-  cameraController_.SetWorldBounds(level_.cameraBounds);
+  beginCameraBoundsBlend(level_.cameraBounds);
+}
+
+void WhiteboxScene::updateCameraBoundsBlend(float deltaTime) {
+  if (!cameraBoundsBlendActive_) {
+    return;
+  }
+
+  cameraBoundsBlendTimer_ += deltaTime;
+  const float t = cameraBoundsBlendDuration_ > 0.0f
+                      ? std::min(cameraBoundsBlendTimer_ /
+                                     cameraBoundsBlendDuration_,
+                                 1.0f)
+                      : 1.0f;
+  const auto lerp = [t](float from, float to) {
+    return from + (to - from) * t;
+  };
+
+  currentCameraBounds_ = frostbite2D::Rect(
+      lerp(cameraBoundsBlendStart_.left(), cameraBoundsBlendTarget_.left()),
+      lerp(cameraBoundsBlendStart_.top(), cameraBoundsBlendTarget_.top()),
+      lerp(cameraBoundsBlendStart_.width(), cameraBoundsBlendTarget_.width()),
+      lerp(cameraBoundsBlendStart_.height(), cameraBoundsBlendTarget_.height()));
+  cameraController_.SetWorldBounds(currentCameraBounds_);
+
+  if (t >= 1.0f) {
+    cameraBoundsBlendActive_ = false;
+  }
 }
 
 void WhiteboxScene::updateBattleZones() {
@@ -146,7 +184,7 @@ void WhiteboxScene::updateBattleZones() {
 
     runtime.triggered = true;
     activeBattleZoneIndex_ = static_cast<int>(i);
-    cameraController_.SetWorldBounds(level_.battleZones[i].cameraBounds);
+    beginCameraBoundsBlend(level_.battleZones[i].cameraBounds);
     break;
   }
 }

game/src/scene/whitebox_scene.h

@@ -31,7 +31,9 @@ private:
   std::vector<BattleZoneDebugInfo> buildBattleZoneDebugInfo() const;
   void configureCamera();
   void toggleDebugOverlay();
+  void beginCameraBoundsBlend(const frostbite2D::Rect& targetBounds);
   void clearActiveBattleZone();
+  void updateCameraBoundsBlend(float deltaTime);
   void updateBattleZones();
   void updateCamera(float deltaTime);
 
@@ -39,6 +41,12 @@ private:
   DebugFlags debugFlags_;
   std::vector<BattleZoneRuntime> battleZoneStates_;
   int activeBattleZoneIndex_ = -1;
+  bool cameraBoundsBlendActive_ = false;
+  float cameraBoundsBlendTimer_ = 0.0f;
+  float cameraBoundsBlendDuration_ = 0.35f;
+  frostbite2D::Rect cameraBoundsBlendStart_;
+  frostbite2D::Rect cameraBoundsBlendTarget_;
+  frostbite2D::Rect currentCameraBounds_;
   CameraController cameraController_;
   StageRenderer stageRenderer_;
   DebugOverlay debugOverlay_;