Only ever create one BufferViewData per file.

It is not uncommon for multiple logical textures in an FBX to reference
the same filename. Each such filename should yield one buffer view only,
and all sharing textures should reference it.

src/Raw2Gltf.cpp

@@ -93,6 +93,35 @@ struct GLTFData
         return bufferView;
     }
 
+    std::shared_ptr<BufferViewData> AddBufferViewForFile(BufferData &buffer, const std::string &filename)
+    {
+        // see if we've already created a BufferViewData for this precise file
+        auto iter = filenameToBufferView.find(filename);
+        if (iter != filenameToBufferView.end()) {
+            return iter->second;
+        }
+
+        std::shared_ptr<BufferViewData> result;
+        std::ifstream file(filename, std::ios::binary | std::ios::ate);
+        if (file) {
+            std::streamsize size = file.tellg();
+            file.seekg(0, std::ios::beg);
+
+            std::vector<char> fileBuffer(size);
+            if (file.read(fileBuffer.data(), size)) {
+                result = AddRawBufferView(buffer, fileBuffer.data(), size);
+            } else {
+                fmt::printf("Warning: Couldn't read %lu bytes from %s, skipping\n", size, filename);
+            }
+        } else {
+            fmt::printf("Warning: Couldn't open texture file %s, skipping\n", filename);
+        }
+        // note that we persist here not only success, but also failure, as nullptr
+        filenameToBufferView[filename] = result;
+        return result;
+    }
+
+
     template<class T>
     std::shared_ptr<AccessorData> AddAccessorWithView(
         BufferViewData &bufferView, const GLType &type, const std::vector<T> &source)
@@ -164,8 +193,13 @@ struct GLTFData
     }
 
     const bool isGlb;
+
+    // cache BufferViewData instances that've already been created from a given filename
+    std::map<std::string, std::shared_ptr<BufferViewData>> filenameToBufferView;
+
     std::shared_ptr<std::vector<uint8_t> > binary;
 
+
     Holder<BufferData>     buffers;
     Holder<BufferViewData> bufferViews;
     Holder<AccessorData>   accessors;
@@ -332,23 +366,13 @@ ModelData *Raw2Gltf(
 
             ImageData *source = nullptr;
             if (options.outputBinary) {
-                std::ifstream file(texFilename, std::ios::binary | std::ios::ate);
-                if (file) {
-                    std::streamsize size = file.tellg();
-                    file.seekg(0, std::ios::beg);
-
-                    std::vector<char> fileBuffer(size);
-                    if (file.read(fileBuffer.data(), size)) {
-                        auto bufferView = gltf->AddRawBufferView(buffer, fileBuffer.data(), size);
-                        source = new ImageData(textureName, *bufferView, "image/png");
-                    } else {
-                        fmt::printf("Warning: Couldn't read %lu bytes from %s, skipping\n", size, texFilename.c_str());
-                    }
-                } else {
-                    fmt::printf("Warning: Couldn't open texture file %s, skipping\n", texFilename.c_str());
+                auto bufferView = gltf->AddBufferViewForFile(buffer, texFilename);
+                if (bufferView) {
+                    source = new ImageData(textureName, *bufferView, "image/png");
                 }
+
             } else {
-                // TODO: write to buffer.bin?
+                // TODO: don't add .ktx here; try to work out a reasonable relative path.
                 source = new ImageData(textureName, textureName + ".ktx");
             }
             if (!source) {