Fix texture streaming minimum mips to load for block compressed textures

Source/Engine/Graphics/Textures/StreamingTexture.cpp

@@ -110,6 +110,14 @@ bool StreamingTexture::Create(const TextureHeader& header)
     // That's one of the main advantages of the current resources streaming system.
     _header = header;
     _isBlockCompressed = PixelFormatExtensions::IsCompressed(_header.Format);
+    if (_isBlockCompressed)
+    {
+        // Ensure that streaming doesn't go too low because the hardware expects the texture to be min in size of compressed texture block
+        int32 lastMip = header.MipLevels - 1;
+        while (header.Width >> lastMip < 4 && header.Height >> lastMip < 4)
+            lastMip--;
+        _minMipCountBlockCompressed = header.MipLevels - lastMip + 1;
+    }
 
     // Request resource streaming
 #if GPU_ENABLE_TEXTURES_STREAMING

Source/Engine/Graphics/Textures/StreamingTexture.h

@@ -12,6 +12,7 @@
 class FLAXENGINE_API StreamingTexture : public Object, public StreamableResource
 {
     friend class TextureBase;
+    friend class TexturesStreamingHandler;
     friend class StreamTextureMipTask;
     friend class StreamTextureResizeTask;
 protected:
@@ -20,6 +21,7 @@ protected:
     GPUTexture* _texture;
     TextureHeader _header;
     volatile mutable int64 _streamingTasksCount;
+    int32 _minMipCountBlockCompressed;
     bool _isBlockCompressed;
 
 public:
@@ -122,14 +124,6 @@ public:
         return &_header;
     }
 
-    /// <summary>
-    /// Gets a boolean indicating whether this <see cref="StreamingTexture"/> is a using a block compress format (BC1, BC2, BC3, BC4, BC5, BC6H, BC7).
-    /// </summary>
-    FORCE_INLINE bool IsBlockCompressed() const
-    {
-        return _isBlockCompressed;
-    }
-
 public:
 
     /// <summary>

Source/Engine/Streaming/StreamingHandlers.cpp

@@ -57,10 +57,10 @@ int32 TexturesStreamingHandler::CalculateResidency(StreamableResource* resource,
 #endif
     }
 
-    if (mipLevels > 0 && mipLevels < 3 && totalMipLevels > 1 && texture.IsBlockCompressed())
+    if (mipLevels > 0 && mipLevels < texture._minMipCountBlockCompressed && texture._isBlockCompressed)
     {
-        // Block compressed textures require minimum size of 4 (3 mips or more)
-        mipLevels = 3;
+        // Block compressed textures require minimum size of 4
+        mipLevels = texture._minMipCountBlockCompressed;
     }
 
     return Math::Clamp(mipLevels, 0, totalMipLevels);