diff --git a/renderdoc/api/replay/data_types.h b/renderdoc/api/replay/data_types.h
index 8391e617f..955569ef5 100644
--- a/renderdoc/api/replay/data_types.h
+++ b/renderdoc/api/replay/data_types.h
@@ -301,6 +301,30 @@ Invalid values will result in 1 being set.
       flags |= ResourceFormat_3Planes;
   }
 
+  DOCUMENT(R"(:return: ``True`` if the ``ResourceFormat`` is a block-compressed type.
+:rtype: bool
+)");
+  bool BlockFormat() const
+  {
+    switch(type)
+    {
+      default: break;
+      case ResourceFormatType::BC1:
+      case ResourceFormatType::BC4:
+      case ResourceFormatType::BC2:
+      case ResourceFormatType::BC3:
+      case ResourceFormatType::BC5:
+      case ResourceFormatType::BC6:
+      case ResourceFormatType::BC7:
+      case ResourceFormatType::ETC2:
+      case ResourceFormatType::EAC:
+      case ResourceFormatType::ASTC:
+      case ResourceFormatType::PVRTC: return true;
+    }
+
+    return false;
+  }
+
   DOCUMENT(R"(Return the size of a single element in this format, usually a pixel. For regular sized
 formats this is just :data:`compByteWidth` times :data:`compCount`, for special packed formats it's
 the tightly packed size of a single element, with no padding.
diff --git a/renderdoc/common/dds_readwrite.cpp b/renderdoc/common/dds_readwrite.cpp
index 74060634d..4625c5d03 100644
--- a/renderdoc/common/dds_readwrite.cpp
+++ b/renderdoc/common/dds_readwrite.cpp
@@ -677,7 +677,7 @@ DXGI_FORMAT ResourceFormat2DXGIFormat(ResourceFormat format)
   return DXGI_FORMAT_UNKNOWN;
 }
 
-bool write_dds_to_file(FILE *f, const dds_data &data)
+bool write_dds_to_file(FILE *f, const write_dds_data &data)
 {
   if(!f)
     return false;
@@ -914,7 +914,7 @@ bool write_dds_to_file(FILE *f, const dds_data &data)
         uint32_t numdepths = RDCMAX(1U, data.depth >> mip);
         for(uint32_t d = 0; d < numdepths; d++)
         {
-          byte *bytedata = data.subdata[i];
+          byte *bytedata = data.subresources[d];
 
           uint32_t rowlen = RDCMAX(1U, data.width >> mip);
           uint32_t numRows = RDCMAX(1U, data.height >> mip);
@@ -958,10 +958,10 @@ bool is_dds_file(byte *headerBuffer, size_t size)
   return memcmp(headerBuffer, &dds_fourcc, 4) == 0;
 }
 
-dds_data load_dds_from_file(StreamReader *reader)
+read_dds_data load_dds_from_file(StreamReader *reader)
 {
-  dds_data ret = {};
-  dds_data error = {};
+  read_dds_data ret = {};
+  read_dds_data error = {};
 
   uint64_t fileSize = reader->GetSize();
 
@@ -1195,8 +1195,28 @@ dds_data load_dds_from_file(StreamReader *reader)
     return ret;
   }
 
-  ret.subsizes = new uint32_t[ret.slices * ret.mips];
-  ret.subdata = new byte *[ret.slices * ret.mips];
+  // we reserve space for a full mip-chain (twice the size of the top mip) just to be conservative
+  {
+    uint32_t rowlen = AlignUp(ret.width, subsamplePacking);
+    uint32_t numRows = ret.height;
+    uint32_t pitch = RDCMAX(1U, rowlen * bytesPerPixel);
+
+    // pitch/rows are in blocks, not pixels, for block formats.
+    if(blockFormat)
+    {
+      numRows = RDCMAX(1U, (numRows + 3) / 4);
+
+      uint32_t blockSize =
+          (ret.format.type == ResourceFormatType::BC1 || ret.format.type == ResourceFormatType::BC4)
+              ? 8
+              : 16;
+
+      pitch = RDCMAX(blockSize, (((rowlen + 3) / 4)) * blockSize);
+    }
+
+    ret.buffer.reserve(ret.slices * 2 * ret.depth * numRows * pitch);
+  }
+  ret.subresources.reserve(ret.slices * ret.mips);
 
   int i = 0;
   for(uint32_t slice = 0; slice < ret.slices; slice++)
@@ -1222,9 +1242,14 @@ dds_data load_dds_from_file(StreamReader *reader)
         pitch = RDCMAX(blockSize, (((rowlen + 3) / 4)) * blockSize);
       }
 
-      ret.subsizes[i] = numdepths * numRows * pitch;
+      size_t subOffs = ret.buffer.size();
+      size_t subSize = numdepths * numRows * pitch;
 
-      byte *bytedata = ret.subdata[i] = new byte[ret.subsizes[i]];
+      ret.subresources.push_back({subOffs, subSize});
+
+      ret.buffer.resize(ret.buffer.size() + subSize);
+
+      byte *bytedata = ret.buffer.data() + subOffs;
 
       for(uint32_t d = 0; d < numdepths; d++)
       {
diff --git a/renderdoc/common/dds_readwrite.h b/renderdoc/common/dds_readwrite.h
index 9f34a4cba..358735f92 100644
--- a/renderdoc/common/dds_readwrite.h
+++ b/renderdoc/common/dds_readwrite.h
@@ -40,11 +40,21 @@ struct dds_data
   bool cubemap;
 
   ResourceFormat format;
+};
 
-  byte **subdata;
-  uint32_t *subsizes;
+struct read_dds_data : public dds_data
+{
+  bytebuf buffer;
+
+  // pairs of {offset, size} into above data buffer
+  rdcarray<rdcpair<size_t, size_t>> subresources;
+};
+
+struct write_dds_data : public dds_data
+{
+  rdcarray<byte *> subresources;
 };
 
 extern bool is_dds_file(byte *headerBuffer, size_t size);
-extern dds_data load_dds_from_file(StreamReader *reader);
-extern bool write_dds_to_file(FILE *f, const dds_data &data);
+extern read_dds_data load_dds_from_file(StreamReader *reader);
+extern bool write_dds_to_file(FILE *f, const write_dds_data &data);
diff --git a/renderdoc/core/image_viewer.cpp b/renderdoc/core/image_viewer.cpp
index c396bf4b5..caba56ea6 100644
--- a/renderdoc/core/image_viewer.cpp
+++ b/renderdoc/core/image_viewer.cpp
@@ -327,6 +327,7 @@ public:
   void FileChanged() { RefreshFile(); }
 private:
   void RefreshFile();
+  void CreateProxyTexture(TextureDescription &texDetails, read_dds_data &read_data);
 
   APIProperties m_Props;
   FrameRecord m_FrameRecord;
@@ -421,20 +422,14 @@ ReplayStatus IMG_CreateReplayDevice(RDCFile *rdc, IReplayDriver **driver)
   {
     FileIO::fseek64(f, 0, SEEK_SET);
     StreamReader reader(f);
-    dds_data read_data = load_dds_from_file(&reader);
+    read_dds_data read_data = load_dds_from_file(&reader);
     f = NULL;
 
-    if(read_data.subdata == NULL)
+    if(read_data.subresources.empty())
     {
       RDCERR("DDS file recognised, but couldn't load");
       return ReplayStatus::ImageUnsupported;
     }
-
-    for(uint32_t i = 0; i < read_data.slices * read_data.mips; i++)
-      delete[] read_data.subdata[i];
-
-    delete[] read_data.subdata;
-    delete[] read_data.subsizes;
   }
   else
   {
@@ -703,7 +698,7 @@ void ImageViewer::RefreshFile()
   m_FrameRecord.frameInfo.persistentSize = 0;
   m_FrameRecord.frameInfo.uncompressedFileSize = datasize;
 
-  dds_data read_data = {0};
+  read_dds_data read_data;
 
   if(dds)
   {
@@ -712,10 +707,8 @@ void ImageViewer::RefreshFile()
     read_data = load_dds_from_file(&reader);
     f = NULL;
 
-    if(read_data.subdata == NULL)
-    {
+    if(read_data.subresources.empty())
       return;
-    }
 
     texDetails.cubemap = read_data.cubemap;
     texDetails.arraysize = read_data.slices;
@@ -750,17 +743,14 @@ void ImageViewer::RefreshFile()
 
     m_FrameRecord.frameInfo.uncompressedFileSize = 0;
     for(uint32_t i = 0; i < texDetails.arraysize * texDetails.mips; i++)
-      m_FrameRecord.frameInfo.uncompressedFileSize += read_data.subsizes[i];
+      m_FrameRecord.frameInfo.uncompressedFileSize += read_data.subresources[i].second;
   }
 
   m_FrameRecord.frameInfo.compressedFileSize = m_FrameRecord.frameInfo.uncompressedFileSize;
 
   // recreate proxy texture if necessary.
-  // we rewrite the texture IDs so that the
-  // outside world doesn't need to know about this
-  // (we only ever have one texture in the image
-  // viewer so we can just set all texture IDs
-  // used to that).
+  // we rewrite the texture IDs so that the outside world doesn't need to know about this (we only
+  // ever have one texture in the image viewer so we can just set all texture IDs used to that).
   if(m_TextureID != ResourceId())
   {
     if(m_TexDetails.width != texDetails.width || m_TexDetails.height != texDetails.height ||
@@ -773,81 +763,7 @@ void ImageViewer::RefreshFile()
   }
 
   if(m_TextureID == ResourceId())
-  {
-    if(m_Proxy->IsTextureSupported(texDetails))
-    {
-      m_TextureID = m_Proxy->CreateProxyTexture(texDetails);
-    }
-    else
-    {
-      if(dds)
-      {
-        // see if we can convert this format on the CPU for proxying
-        bool convertSupported = false;
-        DecodeFormattedComponents(texDetails.format, NULL, &convertSupported);
-
-        if(convertSupported)
-        {
-          uint32_t srcStride = texDetails.format.ElementSize();
-
-          if(texDetails.format.type == ResourceFormatType::D16S8)
-            srcStride = 4;
-          else if(texDetails.format.type == ResourceFormatType::D32S8)
-            srcStride = 8;
-
-          m_RealTexData.resize(texDetails.arraysize * texDetails.mips);
-
-          for(uint32_t i = 0; i < texDetails.arraysize * texDetails.mips; i++)
-          {
-            const uint32_t mip = i % texDetails.mips;
-
-            const uint32_t mipwidth = RDCMAX(1U, texDetails.width >> mip);
-            const uint32_t mipheight = RDCMAX(1U, texDetails.height >> mip);
-            const uint32_t mipdepth = RDCMAX(1U, texDetails.depth >> mip);
-
-            byte *old = read_data.subdata[i];
-            m_RealTexData[i].assign(old, read_data.subsizes[i]);
-
-            read_data.subsizes[i] = sizeof(FloatVector) * mipwidth * mipheight * mipdepth;
-            byte *converted = new byte[read_data.subsizes[i]];
-
-            byte *src = old;
-            FloatVector *dst = (FloatVector *)converted;
-
-            for(uint32_t z = 0; z < mipdepth; z++)
-            {
-              for(uint32_t y = 0; y < mipheight; y++)
-              {
-                for(uint32_t x = 0; x < mipwidth; x++)
-                {
-                  *dst = DecodeFormattedComponents(texDetails.format, src);
-                  dst++;
-                  src += srcStride;
-                }
-              }
-            }
-
-            read_data.subdata[i] = converted;
-            delete[] old;
-          }
-
-          TextureDescription remapped = texDetails;
-          remapped.format = rgba32_float;
-          m_TextureID = m_Proxy->CreateProxyTexture(remapped);
-        }
-        else
-        {
-          RDCLOG("Format %s not supported for local display and can't be converted manually.",
-                 texDetails.format.Name().c_str());
-        }
-      }
-      else
-      {
-        RDCERR("Standard format %s expected to be supported for local display but can't.",
-               texDetails.format.Name().c_str());
-      }
-    }
-  }
+    CreateProxyTexture(texDetails, read_data);
 
   if(m_TextureID == ResourceId())
     RDCERR("Couldn't create proxy texture for image file");
@@ -866,15 +782,133 @@ void ImageViewer::RefreshFile()
     for(uint32_t i = 0; i < texDetails.arraysize * texDetails.mips; i++)
     {
       m_Proxy->SetProxyTextureData(m_TextureID, {i % texDetails.mips, i / texDetails.mips},
-                                   read_data.subdata[i], (size_t)read_data.subsizes[i]);
-
-      delete[] read_data.subdata[i];
+                                   read_data.buffer.data() + read_data.subresources[i].first,
+                                   read_data.subresources[i].second);
     }
-
-    delete[] read_data.subdata;
-    delete[] read_data.subsizes;
   }
 
   if(f != NULL)
     FileIO::fclose(f);
 }
+
+void ImageViewer::CreateProxyTexture(TextureDescription &texDetails, read_dds_data &read_data)
+{
+  if(m_Proxy->IsTextureSupported(texDetails))
+  {
+    m_TextureID = m_Proxy->CreateProxyTexture(texDetails);
+    return;
+  }
+  else
+  {
+    // for block compressed 3D textures these may not be supported, try to remap to a 2D array
+    if(texDetails.format.BlockFormat() && texDetails.type == TextureType::Texture3D)
+    {
+      TextureDescription arrayDetails = texDetails;
+      arrayDetails.arraysize = arrayDetails.depth;
+      arrayDetails.depth = 1;
+      arrayDetails.type = TextureType::Texture2DArray;
+      arrayDetails.dimension = 2;
+
+      if(m_Proxy->IsTextureSupported(arrayDetails))
+      {
+        texDetails = arrayDetails;
+        m_TextureID = m_Proxy->CreateProxyTexture(arrayDetails);
+
+        rdcarray<rdcpair<size_t, size_t>> oldSubs;
+        oldSubs.swap(read_data.subresources);
+
+        // reformat the subresources. The data doesn't change we just add new offsets/sizes
+        for(uint32_t i = 0; i < texDetails.arraysize * texDetails.mips; i++)
+        {
+          const uint32_t mip = i % texDetails.mips;
+          const uint32_t slice = i / texDetails.mips;
+
+          // size of each subresource is 1/Nth for an N-sized array
+          size_t size = oldSubs[mip].second / texDetails.arraysize;
+
+          // and the offset is slice steps further on
+          size_t offset = oldSubs[mip].first + size * slice;
+
+          read_data.subresources.push_back({offset, size});
+        }
+
+        return;
+      }
+    }
+
+    if(read_data.width != 0)
+    {
+      // see if we can convert this format on the CPU for proxying
+      bool convertSupported = false;
+      DecodeFormattedComponents(texDetails.format, NULL, &convertSupported);
+
+      if(convertSupported)
+      {
+        uint32_t srcStride = texDetails.format.ElementSize();
+
+        if(texDetails.format.type == ResourceFormatType::D16S8)
+          srcStride = 4;
+        else if(texDetails.format.type == ResourceFormatType::D32S8)
+          srcStride = 8;
+
+        m_RealTexData.resize(texDetails.arraysize * texDetails.mips);
+
+        bytebuf convertedData;
+
+        for(uint32_t i = 0; i < texDetails.arraysize * texDetails.mips; i++)
+        {
+          const uint32_t mip = i % texDetails.mips;
+
+          const uint32_t mipwidth = RDCMAX(1U, texDetails.width >> mip);
+          const uint32_t mipheight = RDCMAX(1U, texDetails.height >> mip);
+          const uint32_t mipdepth = RDCMAX(1U, texDetails.depth >> mip);
+
+          byte *old = read_data.buffer.data() + read_data.subresources[i].first;
+          m_RealTexData[i].assign(old, read_data.subresources[i].second);
+
+          read_data.subresources[i].first = convertedData.size();
+          read_data.subresources[i].second = sizeof(FloatVector) * mipwidth * mipheight * mipdepth;
+          convertedData.resize(convertedData.size() + read_data.subresources[i].second);
+          byte *converted = convertedData.data() + read_data.subresources[i].first;
+
+          byte *src = old;
+          FloatVector *dst = (FloatVector *)converted;
+
+          for(uint32_t z = 0; z < mipdepth; z++)
+          {
+            for(uint32_t y = 0; y < mipheight; y++)
+            {
+              for(uint32_t x = 0; x < mipwidth; x++)
+              {
+                *dst = DecodeFormattedComponents(texDetails.format, src);
+                dst++;
+                src += srcStride;
+              }
+            }
+          }
+        }
+
+        read_data.buffer.swap(convertedData);
+
+        ResourceFormat rgba32_float;
+        rgba32_float.type = ResourceFormatType::Regular;
+        rgba32_float.compByteWidth = 4;
+        rgba32_float.compCount = 4;
+        rgba32_float.compType = CompType::Float;
+
+        texDetails.format = rgba32_float;
+        m_TextureID = m_Proxy->CreateProxyTexture(texDetails);
+      }
+      else
+      {
+        RDCLOG("Format %s not supported for local display and can't be converted manually.",
+               texDetails.format.Name().c_str());
+      }
+    }
+    else
+    {
+      RDCERR("Standard format %s expected to be supported for local display but can't.",
+             texDetails.format.Name().c_str());
+    }
+  }
+}
diff --git a/renderdoc/os/win32/win32_shellext.cpp b/renderdoc/os/win32/win32_shellext.cpp
index a5abe7be2..a3961e3de 100644
--- a/renderdoc/os/win32/win32_shellext.cpp
+++ b/renderdoc/os/win32/win32_shellext.cpp
@@ -53,7 +53,7 @@ struct RDCThumbnailProvider : public IThumbnailProvider, IInitializeWithStream
   unsigned int m_iRefcount;
   bool m_Inited;
   RDCThumb m_Thumb;
-  dds_data m_ddsData;
+  read_dds_data m_ddsData;
 
   RDCThumbnailProvider() : m_iRefcount(1), m_Inited(false) { InterlockedIncrement(&numProviders); }
   virtual ~RDCThumbnailProvider() { InterlockedDecrement(&numProviders); }
@@ -140,7 +140,7 @@ struct RDCThumbnailProvider : public IThumbnailProvider, IInitializeWithStream
       StreamReader reader(captureHeader.data(), (ULONG)size);
       m_ddsData = load_dds_from_file(&reader);
 
-      if(m_ddsData.subdata == NULL)
+      if(m_ddsData.subresources.empty())
       {
         return E_INVALIDARG;
       }
@@ -148,18 +148,13 @@ struct RDCThumbnailProvider : public IThumbnailProvider, IInitializeWithStream
       // bitmap.
       m_Thumb.height = (uint16_t)m_ddsData.height;
       m_Thumb.width = (uint16_t)m_ddsData.width;
-      size_t len = m_ddsData.subsizes[0];    // size of slice 0
-      m_Thumb.pixels.resize(len);
-      memcpy(m_Thumb.pixels.data(), m_ddsData.subdata[0], len);    // slice 0
-      m_Thumb.format = FileType::DDS;
 
-      // We don't need any other data
-      for(uint32_t i = 0; i < m_ddsData.slices * m_ddsData.mips; i++)
-      {
-        delete[] m_ddsData.subdata[i];
-      }
-      delete[] m_ddsData.subsizes;
-      delete[] m_ddsData.subdata;
+      // size of slice 0
+      size_t len = m_ddsData.subresources[0].second;
+      m_Thumb.pixels.resize(len);
+      // slice 0 data
+      memcpy(m_Thumb.pixels.data(), m_ddsData.buffer.data() + m_ddsData.subresources[0].first, len);
+      m_Thumb.format = FileType::DDS;
     }
     else
     {
diff --git a/renderdoc/replay/replay_controller.cpp b/renderdoc/replay/replay_controller.cpp
index ad1c2b792..4753d7889 100644
--- a/renderdoc/replay/replay_controller.cpp
+++ b/renderdoc/replay/replay_controller.cpp
@@ -1159,7 +1159,7 @@ bool ReplayController::SaveTexture(const TextureSave &saveData, const rdcstr &pa
   {
     if(sd.destType == FileType::DDS)
     {
-      dds_data ddsData;
+      write_dds_data ddsData;
 
       ResourceFormat saveFmt = td.format;
       // use typeCast to inform typeless saving, otherwise it will get lost
@@ -1172,7 +1172,7 @@ bool ReplayController::SaveTexture(const TextureSave &saveData, const rdcstr &pa
       ddsData.format = saveFmt;
       ddsData.mips = numMips;
       ddsData.slices = numSlices / td.depth;
-      ddsData.subdata = &subdata[0];
+      ddsData.subresources = subdata;
       ddsData.cubemap = td.cubemap && numSlices == 6;
 
       if(singleSlice)