DynamicAtlasManager: add Reset() for atlas state cleanup

Author: TheMostDiligent

Graphics/GraphicsAccessories/interface/DynamicAtlasManager.hpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2025 Diligent Graphics LLC
+ *  Copyright 2019-2026 Diligent Graphics LLC
  *  Copyright 2015-2019 Egor Yusov
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -86,7 +86,7 @@ class DynamicAtlasManager
         {}
 
         /// Checks if the region is empty (width or height is zero).
-        bool IsEmpty() const
+        constexpr bool IsEmpty() const
         {
             return width == 0 || height == 0;
         }
@@ -105,6 +105,11 @@ class DynamicAtlasManager
             return !(*this == rhs);
         }
 
+        constexpr operator bool() const
+        {
+            return !IsEmpty();
+        }
+
         struct Hasher
         {
             size_t operator()(const Region& R) const
@@ -160,6 +165,9 @@ class DynamicAtlasManager
     /// and thus may be fragmented.
     Uint64 GetTotalFreeArea() const { return m_TotalFreeArea; }
 
+    /// Resets the atlas to the initial state, where the entire atlas is free and there are no allocated regions.
+    void Reset();
+
     /// Checks if the atlas is empty, i.e. if there are no allocated regions.
     bool IsEmpty() const
     {

Graphics/GraphicsAccessories/src/DynamicAtlasManager.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2025 Diligent Graphics LLC
+ *  Copyright 2019-2026 Diligent Graphics LLC
  *  Copyright 2015-2019 Egor Yusov
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -369,6 +369,18 @@ void DynamicAtlasManager::Free(Region&& R)
     R = InvalidRegion;
 }
 
+void DynamicAtlasManager::Reset()
+{
+    m_AllocatedRegions.clear();
+    m_FreeRegionsByWidth.clear();
+    m_FreeRegionsByHeight.clear();
+
+    m_TotalFreeArea = Uint64{m_Width} * Uint64{m_Height};
+
+    m_Root    = std::make_unique<Node>();
+    m_Root->R = Region{0, 0, m_Width, m_Height};
+    RegisterNode(*m_Root);
+}
 
 #if DILIGENT_DEBUG
 

Tests/DiligentCoreTest/src/GraphicsAccessories/DynamicAtlasManagerTest.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2022 Diligent Graphics LLC
+ *  Copyright 2019-2026 Diligent Graphics LLC
  *  Copyright 2015-2019 Egor Yusov
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -465,4 +465,17 @@ TEST(GraphicsAccessories_DynamicAtlasManager, AllocateRandom)
     }
 }
 
+TEST(GraphicsAccessories_DynamicAtlasManager, Reset)
+{
+    DynamicAtlasManager Mgr{256, 256};
+    EXPECT_TRUE(Mgr.Allocate(128, 128));
+    EXPECT_TRUE(Mgr.Allocate(64, 64));
+    EXPECT_TRUE(Mgr.Allocate(32, 32));
+    Mgr.Reset();
+    EXPECT_EQ(Mgr.GetFreeRegionCount(), 1U);
+    EXPECT_EQ(Mgr.GetTotalFreeArea(), 256u * 256u);
+    EXPECT_TRUE(Mgr.Allocate(256, 256));
+    Mgr.Reset();
+}
+
 } // namespace