diff --git a/CMakeLists.txt b/CMakeLists.txt
index b4e434b..c1cf0be 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@ if ("${CMAKE_CURRENT_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
     "Hint: mkdir -p build; cmake -H. -Bbuild; make -Cbuild\n")
 endif ()
 
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}")
 include(ExternalProject)
@@ -35,6 +35,13 @@ find_package(Iconv QUIET)
 # create a compilation database for e.g. clang-tidy
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
+if (WIN32)
+  add_compile_definitions(
+    _CRT_SECURE_NO_WARNINGS
+    _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+  )
+endif()
+
 if (WIN32)
   # this will suffice for now; don't really care about 32-bit
   set(LIBXML2_INCLUDE_DIRS ${FBXSDK_INCLUDE_DIR})
@@ -190,7 +197,6 @@ set(LIB_SOURCE_FILES
         src/utils/File_Utils.hpp
         src/utils/Image_Utils.cpp
         src/utils/Image_Utils.hpp
-        src/utils/String_Utils.cpp
         src/utils/String_Utils.hpp
         third_party/CLI11/CLI11.hpp
 )
@@ -237,6 +243,12 @@ if (WIN32)
     optimized ${ZLIB_LIBRARIES}
     debug ${ZLIB_LIBRARIES_DEBUG}
   )
+  # quiet warnings related to fopen, sscanf
+  target_compile_definitions(libFBX2glTF PRIVATE
+  _CRT_SECURE_NO_WARNINGS
+  _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+  )
+
 else()
   target_link_libraries(libFBX2glTF
     ${LIBXML2_LIBRARIES}
diff --git a/src/FBX2glTF.cpp b/src/FBX2glTF.cpp
index 270fcd7..a689b93 100644
--- a/src/FBX2glTF.cpp
+++ b/src/FBX2glTF.cpp
@@ -13,13 +13,6 @@
 #include <unordered_map>
 #include <vector>
 
-#if defined(__unix__) || defined(__APPLE__)
-
-#include <sys/stat.h>
-
-#define _stricmp strcasecmp
-#endif
-
 #include <CLI11.hpp>
 
 #include "FBX2glTF.h"
@@ -271,10 +264,7 @@ int main(int argc, char* argv[]) {
 
   if (outputPath.empty()) {
     // if -o is not given, default to the basename of the .fbx
-    outputPath = fmt::format(
-        ".{}{}",
-        (const char)StringUtils::GetPathSeparator(),
-        StringUtils::GetFileBaseString(inputPath));
+    outputPath = "./" + FileUtils::GetFileBaseString(inputPath);
   }
   // the output folder in .gltf mode, not used for .glb
   std::string outputFolder;
@@ -282,14 +272,17 @@ int main(int argc, char* argv[]) {
   // the path of the actual .glb or .gltf file
   std::string modelPath;
   if (gltfOptions.outputBinary) {
-    // in binary mode, we write precisely where we're asked
-    modelPath = outputPath + ".glb";
-
+    const auto& suffix = FileUtils::GetFileSuffix(outputPath);
+	// add .glb to output path, unless it already ends in exactly that
+    if (suffix.has_value() && suffix.value() == "glb") {
+      modelPath = outputPath;
+    } else {
+      modelPath = outputPath + ".glb";
+    }
   } else {
     // in gltf mode, we create a folder and write into that
-    outputFolder =
-        fmt::format("{}_out{}", outputPath.c_str(), (const char)StringUtils::GetPathSeparator());
-    modelPath = outputFolder + StringUtils::GetFileNameString(outputPath) + ".gltf";
+    outputFolder = fmt::format("{}_out/", outputPath.c_str());
+    modelPath = outputFolder + FileUtils::GetFileNameString(outputPath) + ".gltf";
   }
   if (!FileUtils::CreatePath(modelPath.c_str())) {
     fmt::fprintf(stderr, "ERROR: Failed to create folder: %s'\n", outputFolder.c_str());
@@ -302,7 +295,7 @@ int main(int argc, char* argv[]) {
   if (verboseOutput) {
     fmt::printf("Loading FBX File: %s\n", inputPath);
   }
-  if (!LoadFBXFile(raw, inputPath.c_str(), "png;jpg;jpeg")) {
+  if (!LoadFBXFile(raw, inputPath, {"png", "jpg", "jpeg"})) {
     fmt::fprintf(stderr, "ERROR:: Failed to parse FBX: %s\n", inputPath);
     return 1;
   }
diff --git a/src/FBX2glTF.h b/src/FBX2glTF.h
index 5d3f07a..67a3225 100644
--- a/src/FBX2glTF.h
+++ b/src/FBX2glTF.h
@@ -40,6 +40,15 @@ using json = nlohmann::basic_json<workaround_fifo_map>;
 
 extern bool verboseOutput;
 
+/**
+ * Centralises all the laborious downcasting from your OS' 64-bit
+ * index variables down to the uint32s that glTF is built out of.
+ */
+inline uint32_t to_uint32(size_t n) {
+  assert(n < UINT_MAX);
+  return static_cast<uint32_t>(n);
+}
+
 /**
 * The variuos situations in which the user may wish for us to (re-)compute normals for our vertices.
 */
diff --git a/src/fbx/Fbx2Raw.cpp b/src/fbx/Fbx2Raw.cpp
index 9a11bdd..d99f2f7 100644
--- a/src/fbx/Fbx2Raw.cpp
+++ b/src/fbx/Fbx2Raw.cpp
@@ -925,7 +925,7 @@ static std::string GetInferredFileName(
   }
   // Get the file name with file extension.
   const std::string fileName =
-      StringUtils::GetFileNameString(StringUtils::GetCleanPathString(fbxFileName));
+      FileUtils::GetFileNameString(FileUtils::GetCanonicalPath(fbxFileName));
 
   // Try to find a match with extension.
   for (const auto& file : directoryFileList) {
@@ -935,12 +935,12 @@ static std::string GetInferredFileName(
   }
 
   // Get the file name without file extension.
-  const std::string fileBase = StringUtils::GetFileBaseString(fileName);
+  const std::string fileBase = FileUtils::GetFileBaseString(fileName);
 
   // Try to find a match without file extension.
   for (const auto& file : directoryFileList) {
     // If the two extension-less base names match.
-    if (StringUtils::CompareNoCase(fileBase, StringUtils::GetFileBaseString(file)) == 0) {
+    if (StringUtils::CompareNoCase(fileBase, FileUtils::GetFileBaseString(file)) == 0) {
       // Return the name with extension of the file in the directory.
       return std::string(directory) + file;
     }
@@ -960,14 +960,14 @@ static std::string GetInferredFileName(
 */
 static void FindFbxTextures(
     FbxScene* pScene,
-    const char* fbxFileName,
-    const char* extensions,
+    const std::string fbxFileName,
+    const std::set<std::string>& extensions,
     std::map<const FbxTexture*, FbxString>& textureLocations) {
   // Get the folder the FBX file is in.
-  const std::string folder = StringUtils::GetFolderString(fbxFileName);
+  const std::string folder = FileUtils::GetFolderString(fbxFileName);
 
   // Check if there is a filename.fbm folder to which embedded textures were extracted.
-  const std::string fbmFolderName = folder + StringUtils::GetFileBaseString(fbxFileName) + ".fbm/";
+  const std::string fbmFolderName = folder + FileUtils::GetFileBaseString(fbxFileName) + ".fbm/";
 
   // Search either in the folder with embedded textures or in the same folder as the FBX file.
   const std::string searchFolder = FileUtils::FolderExists(fbmFolderName) ? fbmFolderName : folder;
@@ -996,14 +996,17 @@ static void FindFbxTextures(
   }
 }
 
-bool LoadFBXFile(RawModel& raw, const char* fbxFileName, const char* textureExtensions) {
+bool LoadFBXFile(
+    RawModel& raw,
+    const std::string fbxFileName,
+    const std::set<std::string>& textureExtensions) {
   FbxManager* pManager = FbxManager::Create();
   FbxIOSettings* pIoSettings = FbxIOSettings::Create(pManager, IOSROOT);
   pManager->SetIOSettings(pIoSettings);
 
   FbxImporter* pImporter = FbxImporter::Create(pManager, "");
 
-  if (!pImporter->Initialize(fbxFileName, -1, pManager->GetIOSettings())) {
+  if (!pImporter->Initialize(fbxFileName.c_str(), -1, pManager->GetIOSettings())) {
     if (verboseOutput) {
       fmt::printf("%s\n", pImporter->GetStatus().GetErrorString());
     }
diff --git a/src/fbx/Fbx2Raw.hpp b/src/fbx/Fbx2Raw.hpp
index a5fd231..7933af1 100644
--- a/src/fbx/Fbx2Raw.hpp
+++ b/src/fbx/Fbx2Raw.hpp
@@ -11,6 +11,9 @@
 
 #include "raw/RawModel.hpp"
 
-bool LoadFBXFile(RawModel& raw, const char* fbxFileName, const char* textureExtensions);
+bool LoadFBXFile(
+    RawModel& raw,
+    const std::string fbxFileName,
+    const std::set<std::string>& textureExtensions);
 
 json TranscribeProperty(FbxProperty& prop);
\ No newline at end of file
diff --git a/src/fbx/FbxBlendShapesAccess.hpp b/src/fbx/FbxBlendShapesAccess.hpp
index fc99ec9..85fd32d 100644
--- a/src/fbx/FbxBlendShapesAccess.hpp
+++ b/src/fbx/FbxBlendShapesAccess.hpp
@@ -95,7 +95,7 @@ class FbxBlendShapesAccess {
   }
 
   FbxAnimCurve* GetAnimation(size_t channelIx, size_t animIx) const {
-    return channels.at(channelIx).ExtractAnimation(animIx);
+    return channels.at(channelIx).ExtractAnimation(to_uint32(animIx));
   }
 
  private:
diff --git a/src/fbx/FbxSkinningAccess.hpp b/src/fbx/FbxSkinningAccess.hpp
index d2b42d8..d36c04f 100644
--- a/src/fbx/FbxSkinningAccess.hpp
+++ b/src/fbx/FbxSkinningAccess.hpp
@@ -37,7 +37,7 @@ class FbxSkinningAccess {
     return jointNodes[jointIndex];
   }
 
-  const long GetJointId(const int jointIndex) const {
+  const uint64_t GetJointId(const int jointIndex) const {
     return jointIds[jointIndex];
   }
 
@@ -49,7 +49,7 @@ class FbxSkinningAccess {
     return jointInverseGlobalTransforms[jointIndex];
   }
 
-  const long GetRootNode() const {
+  const uint64_t GetRootNode() const {
     assert(rootIndex != -1);
     return jointIds[rootIndex];
   }
@@ -70,7 +70,7 @@ class FbxSkinningAccess {
 
  private:
   int rootIndex;
-  std::vector<long> jointIds;
+  std::vector<uint64_t> jointIds;
   std::vector<FbxNode*> jointNodes;
   std::vector<FbxMatrix> jointSkinningTransforms;
   std::vector<FbxMatrix> jointInverseGlobalTransforms;
diff --git a/src/gltf/GltfModel.cpp b/src/gltf/GltfModel.cpp
index c3c6524..7bf53ba 100644
--- a/src/gltf/GltfModel.cpp
+++ b/src/gltf/GltfModel.cpp
@@ -12,7 +12,7 @@
 std::shared_ptr<BufferViewData> GltfModel::GetAlignedBufferView(
     BufferData& buffer,
     const BufferViewData::GL_ArrayType target) {
-  unsigned long bufferSize = this->binary->size();
+  uint32_t bufferSize = to_uint32(this->binary->size());
   if ((bufferSize % 4) > 0) {
     bufferSize += (4 - (bufferSize % 4));
     this->binary->resize(bufferSize);
@@ -27,7 +27,7 @@ GltfModel::AddRawBufferView(BufferData& buffer, const char* source, uint32_t byt
   bufferView->byteLength = bytes;
 
   // make space for the new bytes (possibly moving the underlying data)
-  unsigned long bufferSize = this->binary->size();
+  uint32_t bufferSize = to_uint32(this->binary->size());
   this->binary->resize(bufferSize + bytes);
 
   // and copy them into place
@@ -52,7 +52,7 @@ std::shared_ptr<BufferViewData> GltfModel::AddBufferViewForFile(
 
     std::vector<char> fileBuffer(size);
     if (file.read(fileBuffer.data(), size)) {
-      result = AddRawBufferView(buffer, fileBuffer.data(), size);
+      result = AddRawBufferView(buffer, fileBuffer.data(), to_uint32(size));
     } else {
       fmt::printf("Warning: Couldn't read %lu bytes from %s, skipping file.\n", size, filename);
     }
diff --git a/src/gltf/GltfModel.hpp b/src/gltf/GltfModel.hpp
index f82b09f..7c7d52c 100644
--- a/src/gltf/GltfModel.hpp
+++ b/src/gltf/GltfModel.hpp
@@ -44,7 +44,7 @@ template <typename T>
 class Holder {
  public:
   std::shared_ptr<T> hold(T* ptr) {
-    ptr->ix = ptrs.size();
+    ptr->ix = to_uint32(ptrs.size());
     ptrs.emplace_back(ptr);
     return ptrs.back();
   }
@@ -114,7 +114,7 @@ class GltfModel {
       primitive.AddDracoAttrib(attrDef, attribArr);
 
       accessor = accessors.hold(new AccessorData(attrDef.glType));
-      accessor->count = attribArr.size();
+      accessor->count = to_uint32(attribArr.size());
     } else {
       auto bufferView = GetAlignedBufferView(buffer, BufferViewData::GL_ARRAY_BUFFER);
       accessor = AddAccessorWithView(*bufferView, attrDef.glType, attribArr, std::string(""));
diff --git a/src/gltf/Raw2Gltf.cpp b/src/gltf/Raw2Gltf.cpp
index 84ec82b..e081311 100644
--- a/src/gltf/Raw2Gltf.cpp
+++ b/src/gltf/Raw2Gltf.cpp
@@ -256,29 +256,28 @@ ModelData* Raw2Gltf(
         if (material.info->shadingModel == RAW_SHADING_MODEL_PBR_MET_ROUGH) {
           /**
            * PBR FBX Material -> PBR Met/Rough glTF.
+           *
+           * METALLIC and ROUGHNESS textures are packed in G and B channels of a rough/met texture.
+           * Other values translate directly.
            */
           RawMetRoughMatProps* props = (RawMetRoughMatProps*)material.info.get();
 
-          // diffuse and emissive are noncontroversial
-          baseColorTex = simpleTex(RAW_TEXTURE_USAGE_ALBEDO);
-          diffuseFactor = props->diffuseFactor;
-          emissiveFactor = props->emissiveFactor;
-          emissiveIntensity = props->emissiveIntensity;
-
-          // we always send the metallic/roughness factors onto the glTF generator
-          metallic = props->metallic;
-          roughness = props->roughness;
-
           // determine if we need to generate a combined map
           bool hasMetallicMap = material.textures[RAW_TEXTURE_USAGE_METALLIC] >= 0;
           bool hasRoughnessMap = material.textures[RAW_TEXTURE_USAGE_ROUGHNESS] >= 0;
           bool hasOcclusionMap = material.textures[RAW_TEXTURE_USAGE_OCCLUSION] >= 0;
           bool atLeastTwoMaps = hasMetallicMap ? (hasRoughnessMap || hasOcclusionMap)
                                                : (hasRoughnessMap && hasMetallicMap);
-          if (atLeastTwoMaps) {
-            // if there's at least two of metallic/roughness/occlusion, it makes sense to
-            // merge them: occlusion into the red channel, metallic into blue channel, and
-            // roughness into the green.
+          if (!atLeastTwoMaps) {
+            // this handles the case of 0 or 1 maps supplied
+            aoMetRoughTex = hasMetallicMap
+                ? simpleTex(RAW_TEXTURE_USAGE_METALLIC)
+                : (hasRoughnessMap
+                       ? simpleTex(RAW_TEXTURE_USAGE_ROUGHNESS)
+                       : (hasOcclusionMap ? simpleTex(RAW_TEXTURE_USAGE_OCCLUSION) : nullptr));
+          } else {
+            // otherwise merge occlusion into the red channel, metallic into blue channel, and
+            // roughness into the green, of a new combinatory texture
             aoMetRoughTex = textureBuilder.combine(
                 {
                     material.textures[RAW_TEXTURE_USAGE_OCCLUSION],
@@ -289,27 +288,24 @@ ModelData* Raw2Gltf(
                 [&](const std::vector<const TextureBuilder::pixel*> pixels)
                     -> TextureBuilder::pixel {
                   const float occlusion = (*pixels[0])[0];
-                  const float metallic = (*pixels[1])[0];
-                  const float roughness = (*pixels[2])[0];
+                  const float metallic = (*pixels[1])[0] * (hasMetallicMap ? 1 : props->metallic);
+                  const float roughness =
+                      (*pixels[2])[0] * (hasRoughnessMap ? 1 : props->roughness);
                   return {{occlusion,
                            props->invertRoughnessMap ? 1.0f - roughness : roughness,
                            metallic,
                            1}};
                 },
                 false);
-            if (hasOcclusionMap) {
-              // will only be true if there were actual non-trivial pixels
-              occlusionTexture = aoMetRoughTex.get();
-            }
-          } else {
-            // this handles the case of 0 or 1 maps supplied
-            if (hasMetallicMap) {
-              aoMetRoughTex = simpleTex(RAW_TEXTURE_USAGE_METALLIC);
-            } else if (hasRoughnessMap) {
-              aoMetRoughTex = simpleTex(RAW_TEXTURE_USAGE_ROUGHNESS);
-            }
-            // else only occlusion map is possible: that check is handled further below
           }
+          baseColorTex = simpleTex(RAW_TEXTURE_USAGE_ALBEDO);
+          diffuseFactor = props->diffuseFactor;
+          metallic = props->metallic;
+          roughness = props->roughness;
+          emissiveFactor = props->emissiveFactor;
+          emissiveIntensity = props->emissiveIntensity;
+          // this will set occlusionTexture to null, if no actual occlusion map exists
+          occlusionTexture = aoMetRoughTex.get();
         } else {
           /**
            * Traditional FBX Material -> PBR Met/Rough glTF.
@@ -393,7 +389,6 @@ ModelData* Raw2Gltf(
 
         khrCmnUnlitMat.reset(new KHRCmnUnlitMaterial());
       }
-      // after all the special cases have had a go, check if we need to look up occlusion map
       if (!occlusionTexture) {
         occlusionTexture = simpleTex(RAW_TEXTURE_USAGE_OCCLUSION).get();
       }
@@ -447,11 +442,11 @@ ModelData* Raw2Gltf(
 
       std::shared_ptr<PrimitiveData> primitive;
       if (options.draco.enabled) {
-        int triangleCount = surfaceModel.GetTriangleCount();
+        size_t triangleCount = surfaceModel.GetTriangleCount();
 
         // initialize Draco mesh with vertex index information
         auto dracoMesh(std::make_shared<draco::Mesh>());
-        dracoMesh->SetNumFaces(static_cast<size_t>(triangleCount));
+        dracoMesh->SetNumFaces(triangleCount);
         dracoMesh->set_num_points(surfaceModel.GetVertexCount());
 
         for (uint32_t ii = 0; ii < triangleCount; ii++) {
@@ -464,7 +459,7 @@ ModelData* Raw2Gltf(
 
         AccessorData& indexes =
             *gltf->accessors.hold(new AccessorData(useLongIndices ? GLT_UINT : GLT_USHORT));
-        indexes.count = 3 * triangleCount;
+        indexes.count = to_uint32(3 * triangleCount);
         primitive.reset(new PrimitiveData(indexes, mData, dracoMesh));
       } else {
         const AccessorData& indexes = *gltf->AddAccessorWithView(
@@ -499,11 +494,13 @@ ModelData* Raw2Gltf(
               GLT_VEC3F,
               draco::GeometryAttribute::NORMAL,
               draco::DT_FLOAT32);
-          gltf->AddAttributeToPrimitive<Vec3f>(buffer, surfaceModel, *primitive, ATTR_NORMAL);
+          const auto _ =
+              gltf->AddAttributeToPrimitive<Vec3f>(buffer, surfaceModel, *primitive, ATTR_NORMAL);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_TANGENT) != 0) {
           const AttributeDefinition<Vec4f> ATTR_TANGENT("TANGENT", &RawVertex::tangent, GLT_VEC4F);
-          gltf->AddAttributeToPrimitive<Vec4f>(buffer, surfaceModel, *primitive, ATTR_TANGENT);
+          const auto _ = gltf->AddAttributeToPrimitive<Vec4f>(
+              buffer, surfaceModel, *primitive, ATTR_TANGENT);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_COLOR) != 0) {
           const AttributeDefinition<Vec4f> ATTR_COLOR(
@@ -512,7 +509,8 @@ ModelData* Raw2Gltf(
               GLT_VEC4F,
               draco::GeometryAttribute::COLOR,
               draco::DT_FLOAT32);
-          gltf->AddAttributeToPrimitive<Vec4f>(buffer, surfaceModel, *primitive, ATTR_COLOR);
+          const auto _ =
+              gltf->AddAttributeToPrimitive<Vec4f>(buffer, surfaceModel, *primitive, ATTR_COLOR);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_UV0) != 0) {
           const AttributeDefinition<Vec2f> ATTR_TEXCOORD_0(
@@ -521,7 +519,8 @@ ModelData* Raw2Gltf(
               GLT_VEC2F,
               draco::GeometryAttribute::TEX_COORD,
               draco::DT_FLOAT32);
-          gltf->AddAttributeToPrimitive<Vec2f>(buffer, surfaceModel, *primitive, ATTR_TEXCOORD_0);
+          const auto _ = gltf->AddAttributeToPrimitive<Vec2f>(
+              buffer, surfaceModel, *primitive, ATTR_TEXCOORD_0);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_UV1) != 0) {
           const AttributeDefinition<Vec2f> ATTR_TEXCOORD_1(
@@ -530,7 +529,8 @@ ModelData* Raw2Gltf(
               GLT_VEC2F,
               draco::GeometryAttribute::TEX_COORD,
               draco::DT_FLOAT32);
-          gltf->AddAttributeToPrimitive<Vec2f>(buffer, surfaceModel, *primitive, ATTR_TEXCOORD_1);
+          const auto _ = gltf->AddAttributeToPrimitive<Vec2f>(
+              buffer, surfaceModel, *primitive, ATTR_TEXCOORD_1);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_JOINT_INDICES) != 0) {
           const AttributeDefinition<Vec4i> ATTR_JOINTS(
@@ -539,7 +539,8 @@ ModelData* Raw2Gltf(
               GLT_VEC4I,
               draco::GeometryAttribute::GENERIC,
               draco::DT_UINT16);
-          gltf->AddAttributeToPrimitive<Vec4i>(buffer, surfaceModel, *primitive, ATTR_JOINTS);
+          const auto _ =
+              gltf->AddAttributeToPrimitive<Vec4i>(buffer, surfaceModel, *primitive, ATTR_JOINTS);
         }
         if ((surfaceModel.GetVertexAttributes() & RAW_VERTEX_ATTRIBUTE_JOINT_WEIGHTS) != 0) {
           const AttributeDefinition<Vec4f> ATTR_WEIGHTS(
@@ -548,7 +549,8 @@ ModelData* Raw2Gltf(
               GLT_VEC4F,
               draco::GeometryAttribute::GENERIC,
               draco::DT_FLOAT32);
-          gltf->AddAttributeToPrimitive<Vec4f>(buffer, surfaceModel, *primitive, ATTR_WEIGHTS);
+          const auto _ =
+              gltf->AddAttributeToPrimitive<Vec4f>(buffer, surfaceModel, *primitive, ATTR_WEIGHTS);
         }
 
         // each channel present in the mesh always ends up a target in the primitive
@@ -633,7 +635,7 @@ ModelData* Raw2Gltf(
         draco::Status status = encoder.EncodeMeshToBuffer(*primitive->dracoMesh, &dracoBuffer);
         assert(status.code() == draco::Status::OK);
 
-        auto view = gltf->AddRawBufferView(buffer, dracoBuffer.data(), dracoBuffer.size());
+        auto view = gltf->AddRawBufferView(buffer, dracoBuffer.data(), to_uint32(dracoBuffer.size()));
         primitive->NoteDracoBuffer(*view);
       }
       mesh->AddPrimitive(primitive);
@@ -735,7 +737,7 @@ ModelData* Raw2Gltf(
             type = LightData::Type::Spot;
             break;
         }
-        gltf->lights.hold(new LightData(
+        const auto _ = gltf->lights.hold(new LightData(
             light.name,
             type,
             light.color,
@@ -842,13 +844,13 @@ ModelData* Raw2Gltf(
     gltfOutStream.write(glb2BinaryHeader, 8);
 
     // append binary buffer directly to .glb file
-    uint32_t binaryLength = gltf->binary->size();
+    size_t binaryLength = gltf->binary->size();
     gltfOutStream.write((const char*)&(*gltf->binary)[0], binaryLength);
     while ((binaryLength % 4) != 0) {
       gltfOutStream.put('\0');
       binaryLength++;
     }
-    uint32_t totalLength = (uint32_t)gltfOutStream.tellp();
+    uint32_t totalLength = to_uint32(gltfOutStream.tellp());
 
     // seek back to sub-header for json chunk
     gltfOutStream.seekp(8);
diff --git a/src/gltf/Raw2Gltf.hpp b/src/gltf/Raw2Gltf.hpp
index 0dbdc6e..cd44b41 100644
--- a/src/gltf/Raw2Gltf.hpp
+++ b/src/gltf/Raw2Gltf.hpp
@@ -120,7 +120,7 @@ const GLType GLT_QUATF = {CT_FLOAT, 4, "VEC4"};
  * The base of any indexed glTF entity.
  */
 struct Holdable {
-  uint32_t ix;
+  uint32_t ix = UINT_MAX;
 
   virtual json serialize() const = 0;
 };
diff --git a/src/gltf/TextureBuilder.cpp b/src/gltf/TextureBuilder.cpp
index 4329c5f..2e8105e 100644
--- a/src/gltf/TextureBuilder.cpp
+++ b/src/gltf/TextureBuilder.cpp
@@ -49,8 +49,7 @@ std::shared_ptr<TextureData> TextureBuilder::combine(
     if (rawTexIx >= 0) {
       const RawTexture& rawTex = raw.GetTexture(rawTexIx);
       const std::string& fileLoc = rawTex.fileLocation;
-      const std::string& name =
-          StringUtils::GetFileBaseString(StringUtils::GetFileNameString(fileLoc));
+      const std::string& name = FileUtils::GetFileBaseString(FileUtils::GetFileNameString(fileLoc));
       if (!fileLoc.empty()) {
         info.pixels = stbi_load(fileLoc.c_str(), &info.width, &info.height, &info.channels, 0);
         if (!info.pixels) {
@@ -142,7 +141,7 @@ std::shared_ptr<TextureData> TextureBuilder::combine(
   ImageData* image;
   if (options.outputBinary) {
     const auto bufferView =
-        gltf.AddRawBufferView(*gltf.defaultBuffer, imgBuffer.data(), imgBuffer.size());
+        gltf.AddRawBufferView(*gltf.defaultBuffer, imgBuffer.data(), to_uint32(imgBuffer.size()));
     image = new ImageData(mergedName, *bufferView, png ? "image/png" : "image/jpeg");
   } else {
     const std::string imageFilename = mergedFilename + (png ? ".png" : ".jpg");
@@ -180,20 +179,30 @@ std::shared_ptr<TextureData> TextureBuilder::simple(int rawTexIndex, const std::
   }
 
   const RawTexture& rawTexture = raw.GetTexture(rawTexIndex);
-  const std::string textureName = StringUtils::GetFileBaseString(rawTexture.name);
-  const std::string relativeFilename = StringUtils::GetFileNameString(rawTexture.fileLocation);
+  const std::string textureName = FileUtils::GetFileBaseString(rawTexture.name);
+  const std::string relativeFilename = FileUtils::GetFileNameString(rawTexture.fileLocation);
 
   ImageData* image = nullptr;
   if (options.outputBinary) {
     auto bufferView = gltf.AddBufferViewForFile(*gltf.defaultBuffer, rawTexture.fileLocation);
     if (bufferView) {
-      std::string suffix = StringUtils::GetFileSuffixString(rawTexture.fileLocation);
-      image = new ImageData(relativeFilename, *bufferView, ImageUtils::suffixToMimeType(suffix));
+      const auto& suffix = FileUtils::GetFileSuffix(rawTexture.fileLocation);
+      std::string mimeType;
+      if (suffix) {
+        mimeType = ImageUtils::suffixToMimeType(suffix.value());
+      } else {
+        mimeType = "image/jpeg";
+        fmt::printf(
+            "Warning: Can't deduce mime type of texture '%s'; using %s.\n",
+            rawTexture.fileLocation,
+            mimeType);
+      }
+      image = new ImageData(relativeFilename, *bufferView, mimeType);
     }
 
   } else if (!relativeFilename.empty()) {
     image = new ImageData(relativeFilename, relativeFilename);
-    std::string outputPath = outputFolder + StringUtils::NormalizePath(relativeFilename);
+    std::string outputPath = FileUtils::GetCanonicalPath(outputFolder + "/" + relativeFilename);
     if (FileUtils::CopyFile(rawTexture.fileLocation, outputPath, true)) {
       if (verboseOutput) {
         fmt::printf("Copied texture '%s' to output folder: %s\n", textureName, outputPath);
diff --git a/src/gltf/properties/AnimationData.cpp b/src/gltf/properties/AnimationData.cpp
index a1dd09b..a2fcced 100644
--- a/src/gltf/properties/AnimationData.cpp
+++ b/src/gltf/properties/AnimationData.cpp
@@ -24,7 +24,7 @@ void AnimationData::AddNodeChannel(
     const AccessorData& accessor,
     std::string path) {
   assert(channels.size() == samplers.size());
-  uint32_t ix = channels.size();
+  uint32_t ix = to_uint32(channels.size());
   channels.emplace_back(channel_t(ix, node, std::move(path)));
   samplers.emplace_back(sampler_t(timeAccessor, accessor.ix));
 }
diff --git a/src/gltf/properties/MaterialData.cpp b/src/gltf/properties/MaterialData.cpp
index 8ac6bfa..c1697b3 100644
--- a/src/gltf/properties/MaterialData.cpp
+++ b/src/gltf/properties/MaterialData.cpp
@@ -59,13 +59,15 @@ void to_json(json& j, const PBRMetallicRoughness& d) {
   if (d.baseColorFactor.LengthSquared() > 0) {
     j["baseColorFactor"] = toStdVec(d.baseColorFactor);
   }
-  // we always copy metallic/roughness straight to the glTF:
-  //  - if there's a texture, they're linear multiplier
-  //  - if there's no texture, they're constants
-  j["metallicFactor"] = d.metallic;
-  j["roughnessFactor"] = d.roughness;
   if (d.metRoughTexture != nullptr) {
     j["metallicRoughnessTexture"] = *d.metRoughTexture;
+    // if a texture is provided, throw away metallic/roughness values
+    j["roughnessFactor"] = 1.0f;
+    j["metallicFactor"] = 1.0f;
+  } else {
+    // without a texture, however, use metallic/roughness as constants
+    j["metallicFactor"] = d.metallic;
+    j["roughnessFactor"] = d.roughness;
   }
 }
 
diff --git a/src/gltf/properties/PrimitiveData.hpp b/src/gltf/properties/PrimitiveData.hpp
index 16bf7e9..3153229 100644
--- a/src/gltf/properties/PrimitiveData.hpp
+++ b/src/gltf/properties/PrimitiveData.hpp
@@ -49,7 +49,7 @@ struct PrimitiveData {
         componentCount * draco::DataTypeLength(attribute.dracoComponentType),
         0);
 
-    const int dracoAttId = dracoMesh->AddAttribute(att, true, attribArr.size());
+    const int dracoAttId = dracoMesh->AddAttribute(att, true, to_uint32(attribArr.size()));
     draco::PointAttribute* attPtr = dracoMesh->attribute(dracoAttId);
 
     std::vector<uint8_t> buf(sizeof(T));
diff --git a/src/raw/RawModel.cpp b/src/raw/RawModel.cpp
index cafc076..9ddebf7 100644
--- a/src/raw/RawModel.cpp
+++ b/src/raw/RawModel.cpp
@@ -632,7 +632,7 @@ void RawModel::CreateMaterialModels(
   }
 }
 
-int RawModel::GetNodeById(const long nodeId) const {
+int RawModel::GetNodeById(const uint32_t nodeId) const {
   for (size_t i = 0; i < nodes.size(); i++) {
     if (nodes[i].id == nodeId) {
       return (int)i;
@@ -641,7 +641,7 @@ int RawModel::GetNodeById(const long nodeId) const {
   return -1;
 }
 
-int RawModel::GetSurfaceById(const long surfaceId) const {
+int RawModel::GetSurfaceById(const uint32_t surfaceId) const {
   for (size_t i = 0; i < surfaces.size(); i++) {
     if (surfaces[i].id == surfaceId) {
       return (int)i;
diff --git a/src/utils/File_Utils.cpp b/src/utils/File_Utils.cpp
index 4c044fe..aa3ffa8 100644
--- a/src/utils/File_Utils.cpp
+++ b/src/utils/File_Utils.cpp
@@ -10,171 +10,41 @@
 #include "File_Utils.hpp"
 
 #include <fstream>
+#include <set>
 #include <string>
 #include <vector>
 
 #include <stdint.h>
 #include <stdio.h>
 
-#if defined(__unix__) || defined(__APPLE__)
-
-#include <dirent.h>
-#include <errno.h>
-#include <stdlib.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#define _getcwd getcwd
-#define _mkdir(a) mkdir(a, 0777)
-#elif defined(_WIN32)
-#include <direct.h>
-#include <process.h>
-#else
-#include <direct.h>
-#include <process.h>
-#endif
-
-#include <sys/stat.h>
-
 #include "FBX2glTF.h"
 #include "String_Utils.hpp"
 
 namespace FileUtils {
 
-std::string GetCurrentFolder() {
-  char cwd[StringUtils::MAX_PATH_LENGTH];
-  if (!_getcwd(cwd, sizeof(cwd))) {
-    return std::string();
-  }
-  cwd[sizeof(cwd) - 1] = '\0';
-  StringUtils::GetCleanPath(cwd, cwd, StringUtils::PATH_UNIX);
-  const size_t length = strlen(cwd);
-  if (cwd[length - 1] != '/' && length < StringUtils::MAX_PATH_LENGTH - 1) {
-    cwd[length + 0] = '/';
-    cwd[length + 1] = '\0';
-  }
-  return std::string(cwd);
-}
-
-bool FileExists(const std::string& filePath) {
-  std::ifstream stream(filePath);
-  return stream.good();
-}
-
-bool FolderExists(const std::string& folderPath) {
-#if defined(__unix__) || defined(__APPLE__)
-  DIR* dir = opendir(folderPath.c_str());
-  if (dir) {
-    closedir(dir);
-    return true;
-  }
-  return false;
-#else
-  const DWORD ftyp = GetFileAttributesA(folderPath.c_str());
-  if (ftyp == INVALID_FILE_ATTRIBUTES) {
-    return false; // bad path
-  }
-  return (ftyp & FILE_ATTRIBUTE_DIRECTORY) != 0;
-#endif
-}
-
-bool MatchExtension(const char* fileExtension, const char* matchExtensions) {
-  if (matchExtensions[0] == '\0') {
-    return true;
-  }
-  if (fileExtension[0] == '.') {
-    fileExtension++;
-  }
-  for (const char* end = matchExtensions; end[0] != '\0';) {
-    for (; end[0] == ';'; end++) {
-    }
-    const char* ext = end;
-    for (; end[0] != ';' && end[0] != '\0'; end++) {
-    }
-#if defined(__unix__) || defined(__APPLE__)
-    if (strncasecmp(fileExtension, ext, end - ext) == 0)
-#else
-    if (_strnicmp(fileExtension, ext, end - ext) == 0)
-#endif
-    {
-      return true;
-    }
-  }
-  return false;
-}
-
-std::vector<std::string> ListFolderFiles(const char* folder, const char* matchExtensions) {
+std::vector<std::string> ListFolderFiles(
+    const std::string folder,
+    const std::set<std::string>& matchExtensions) {
   std::vector<std::string> fileList;
-#if defined(__unix__) || defined(__APPLE__)
-  DIR* dir = opendir(strlen(folder) > 0 ? folder : ".");
-  if (dir != nullptr) {
-    for (;;) {
-      struct dirent* dp = readdir(dir);
-      if (dp == nullptr) {
-        break;
-      }
-
-      if (dp->d_type == DT_DIR) {
-        continue;
-      }
-
-      const char* fileName = dp->d_name;
-      const char* fileExt = strrchr(fileName, '.');
-
-      if (!fileExt || !MatchExtension(fileExt, matchExtensions)) {
-        continue;
-      }
-
-      fileList.emplace_back(fileName);
+  for (const std::filesystem::directory_entry& entry : std::filesystem::directory_iterator(folder)) {
+    const std::filesystem::path& path = entry.path();
+    if (matchExtensions.find(path.extension().string()) != matchExtensions.end()) {
+      fileList.push_back(path.string());
     }
-
-    closedir(dir);
   }
-#else
-  std::string pathStr = folder;
-  pathStr += "*";
-
-  WIN32_FIND_DATA FindFileData;
-  HANDLE hFind = FindFirstFile(pathStr.c_str(), &FindFileData);
-  if (hFind != INVALID_HANDLE_VALUE) {
-    do {
-      if ((FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == 0) {
-        std::string fileName = FindFileData.cFileName;
-        std::string::size_type extPos = fileName.rfind('.');
-        if (extPos != std::string::npos &&
-            MatchExtension(fileName.substr(extPos + 1).c_str(), matchExtensions)) {
-          fileList.push_back(fileName);
-        }
-      }
-    } while (FindNextFile(hFind, &FindFileData));
-
-    FindClose(hFind);
-  }
-#endif
   return fileList;
 }
 
-bool CreatePath(const char* path) {
-#if defined(__unix__) || defined(__APPLE__)
-  StringUtils::PathSeparator separator = StringUtils::PATH_UNIX;
-#else
-  StringUtils::PathSeparator separator = StringUtils::PATH_WIN;
-#endif
-  std::string folder = StringUtils::GetFolderString(path);
-  std::string clean = StringUtils::GetCleanPathString(folder, separator);
-  std::string build = clean;
-  for (int i = 0; i < clean.length(); i++) {
-    if (clean[i] == separator && i > 0) {
-      build[i] = '\0';
-      if (i > 1 || build[1] != ':') {
-        if (_mkdir(build.c_str()) != 0 && errno != EEXIST) {
-          return false;
-        }
-      }
-    }
-    build[i] = clean[i];
+bool CreatePath(const std::string path) {
+  const auto& parent = std::filesystem::path(path).parent_path();
+  if (parent.empty()) {
+    // this is either CWD or std::filesystem root; either way it exists
+    return true;
   }
-  return true;
+  if (std::filesystem::exists(parent)) {
+    return std::filesystem::is_directory(parent);
+  }
+  return std::filesystem::create_directory(parent);
 }
 
 bool CopyFile(const std::string& srcFilename, const std::string& dstFilename, bool createPath) {
diff --git a/src/utils/File_Utils.hpp b/src/utils/File_Utils.hpp
index 0f9a702..363115e 100644
--- a/src/utils/File_Utils.hpp
+++ b/src/utils/File_Utils.hpp
@@ -9,6 +9,10 @@
 
 #pragma once
 
+#include <filesystem>
+
+#include <optional>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -19,13 +23,51 @@ std::string GetCurrentFolder();
 bool FileExists(const std::string& folderPath);
 bool FolderExists(const std::string& folderPath);
 
-bool MatchExtension(const char* fileExtension, const char* matchExtensions);
-std::vector<std::string> ListFolderFiles(const char* folder, const char* matchExtensions);
+std::vector<std::string> ListFolderFiles(
+    const std::string folder,
+    const std::set<std::string>& matchExtensions);
 
-bool CreatePath(const char* path);
+bool CreatePath(std::string path);
 
 bool CopyFile(
     const std::string& srcFilename,
     const std::string& dstFilename,
     bool createPath = false);
+
+inline std::string GetCurrentFolder() {
+  return std::filesystem::current_path().string() + "/";
+}
+
+inline bool FileExists(const std::string& filePath) {
+  return std::filesystem::exists(filePath) && std::filesystem::is_regular_file(filePath);
+}
+
+inline bool FolderExists(const std::string& folderPath) {
+  return std::filesystem::exists(folderPath) && std::filesystem::is_directory(folderPath);
+}
+
+inline std::string GetFolderString(const std::string& path) {
+  return std::filesystem::path(path).parent_path().string();
+}
+
+inline std::string GetCanonicalPath(const std::string& path) {
+  return std::filesystem::canonical(path).string();
+}
+
+inline std::string GetFileNameString(const std::string& path) {
+  return std::filesystem::canonical(path).filename().string();
+}
+
+inline std::string GetFileBaseString(const std::string& path) {
+  return std::filesystem::canonical(path).stem().string();
+}
+
+inline std::optional<std::string> GetFileSuffix(const std::string& path) {
+  const auto& extension = std::filesystem::canonical(path).extension();
+  if (extension.empty()) {
+    return std::nullopt;
+  }
+  return extension.string().substr(1);
+}
+
 } // namespace FileUtils
diff --git a/src/utils/String_Utils.cpp b/src/utils/String_Utils.cpp
index 8cf8063..7e0dd2f 100644
--- a/src/utils/String_Utils.cpp
+++ b/src/utils/String_Utils.cpp
@@ -9,72 +9,12 @@
 
 #include "String_Utils.hpp"
 
+#include <algorithm>
+
 namespace StringUtils {
 
-PathSeparator operator!(const PathSeparator& s) {
-  return (s == PATH_WIN) ? PATH_UNIX : PATH_WIN;
-}
-
-PathSeparator GetPathSeparator() {
-#if defined(__unix__) || defined(__APPLE__)
-  return PATH_UNIX;
-#else
-  return PATH_WIN;
-#endif
-}
-const std::string NormalizePath(const std::string& path) {
-  PathSeparator separator = GetPathSeparator();
-  char replace;
-  if (separator == PATH_WIN) {
-    replace = PATH_UNIX;
-  } else {
-    replace = PATH_WIN;
-  }
-  std::string normalizedPath = path;
-  for (size_t s = normalizedPath.find(replace, 0); s != std::string::npos;
-       s = normalizedPath.find(replace, s)) {
-    normalizedPath[s] = separator;
-  }
-  return normalizedPath;
-}
-
-const std::string GetFolderString(const std::string& path) {
-  size_t s = path.rfind(PATH_WIN);
-  s = (s != std::string::npos) ? s : path.rfind(PATH_UNIX);
-  return path.substr(0, s + 1);
-}
-
-const std::string GetCleanPathString(const std::string& path, const PathSeparator separator) {
-  std::string cleanPath = path;
-  for (size_t s = cleanPath.find(!separator, 0); s != std::string::npos;
-       s = cleanPath.find(!separator, s)) {
-    cleanPath[s] = separator;
-  }
-  return cleanPath;
-}
-
-const std::string GetFileNameString(const std::string& path) {
-  size_t s = path.rfind(PATH_WIN);
-  s = (s != std::string::npos) ? s : path.rfind(PATH_UNIX);
-  return path.substr(s + 1, std::string::npos);
-}
-
-const std::string GetFileBaseString(const std::string& path) {
-  const std::string fileName = GetFileNameString(path);
-  return fileName.substr(0, fileName.rfind('.')).c_str();
-}
-
-const std::string GetFileSuffixString(const std::string& path) {
-  const std::string fileName = GetFileNameString(path);
-  size_t pos = fileName.rfind('.');
-  if (pos == std::string::npos) {
-    return "";
-  }
-  return fileName.substr(++pos);
-}
-
 int CompareNoCase(const std::string& s1, const std::string& s2) {
-  return strncasecmp(s1.c_str(), s2.c_str(), MAX_PATH_LENGTH);
+  return strncasecmp(s1.c_str(), s2.c_str(), std::max(s1.length(), s2.length()));
 }
 
 } // namespace StringUtils
diff --git a/src/utils/String_Utils.hpp b/src/utils/String_Utils.hpp
index f1a3a65..d7691d8 100644
--- a/src/utils/String_Utils.hpp
+++ b/src/utils/String_Utils.hpp
@@ -21,34 +21,8 @@
 
 namespace StringUtils {
 
-static const unsigned int MAX_PATH_LENGTH = 1024;
-
-enum PathSeparator { PATH_WIN = '\\', PATH_UNIX = '/' };
-
-PathSeparator operator!(const PathSeparator& s);
-
-PathSeparator GetPathSeparator();
-const std::string NormalizePath(const std::string& path);
-
-const std::string GetCleanPathString(
-    const std::string& path,
-    const PathSeparator separator = PATH_WIN);
-
-template <size_t size>
-void GetCleanPath(char (&dest)[size], const char* path, const PathSeparator separator = PATH_WIN) {
-  size_t len = size - 1;
-  strncpy(dest, path, len);
-  char* destPtr = dest;
-  while ((destPtr = strchr(destPtr, !separator)) != nullptr) {
-    *destPtr = separator;
-  }
+inline int CompareNoCase(const std::string& s1, const std::string& s2) {
+  return strncasecmp(s1.c_str(), s2.c_str(), std::max(s1.length(), s2.length()));
 }
 
-const std::string GetFolderString(const std::string& path);
-const std::string GetFileNameString(const std::string& path);
-const std::string GetFileBaseString(const std::string& path);
-const std::string GetFileSuffixString(const std::string& path);
-
-int CompareNoCase(const std::string& s1, const std::string& s2);
-
 } // namespace StringUtils