Fix baked FSTs unable to be rebaked by creating an FST in the original

output folder

libraries/baking/src/ModelBaker.cpp

@@ -167,6 +167,10 @@ void ModelBaker::saveSourceModel() {
 
         connect(networkReply, &QNetworkReply::finished, this, &ModelBaker::handleModelNetworkReply);
     }
+
+    if (_mappingURL.isEmpty()) {
+        outputUnbakedFST();
+    }
 }
 
 void ModelBaker::handleModelNetworkReply() {
@@ -313,6 +317,37 @@ void ModelBaker::handleFinishedMaterialBaker() {
     outputBakedFST();
 }
 
+void ModelBaker::outputUnbakedFST() {
+    // Output an unbaked FST file in the original output folder to make it easier for FSTBaker to rebake this model
+    // TODO: Consider a more robust method that does not depend on FSTBaker navigating to a hardcoded relative path
+    QString outputFSTFilename = _modelURL.fileName();
+    auto extensionStart = outputFSTFilename.indexOf(".");
+    if (extensionStart != -1) {
+        outputFSTFilename.resize(extensionStart);
+    }
+    outputFSTFilename += FST_EXTENSION;
+    QString outputFSTURL = _originalOutputDir + "/" + outputFSTFilename;
+
+    hifi::VariantHash outputMapping;
+    outputMapping[FST_VERSION_FIELD] = FST_VERSION;
+    outputMapping[FILENAME_FIELD] = _modelURL.fileName();
+    outputMapping[COMMENT_FIELD] = "This FST file was generated by Oven for use during rebaking. It is not part of the original model. This file's existence is subject to change.";
+    hifi::ByteArray fstOut = FSTReader::writeMapping(outputMapping);
+
+    QFile fstOutputFile { outputFSTURL };
+    if (fstOutputFile.exists()) {
+        handleWarning("The file '" + outputFSTURL + "' already exists. Should that be baked instead of '" + _modelURL.toString() + "'?");
+        return;
+    }
+    if (!fstOutputFile.open(QIODevice::WriteOnly)) {
+        handleWarning("Failed to open file '" + outputFSTURL + "' for writing. Rebaking may fail on the associated model.");
+        return;
+    }
+    if (fstOutputFile.write(fstOut) == -1) {
+        handleWarning("Failed to write to file '" + outputFSTURL + "'. Rebaking may fail on the associated model.");
+    }
+}
+
 void ModelBaker::outputBakedFST() {
     // Output FST file, copying over input mappings if available
     QString outputFSTFilename = !_mappingURL.isEmpty() ? _mappingURL.fileName() : _modelURL.fileName();
@@ -327,6 +362,7 @@ void ModelBaker::outputBakedFST() {
     outputMapping[FST_VERSION_FIELD] = FST_VERSION;
     outputMapping[FILENAME_FIELD] = _bakedModelURL.fileName();
     outputMapping.remove(TEXDIR_FIELD);
+    outputMapping.remove(COMMENT_FIELD);
     hifi::ByteArray fstOut = FSTReader::writeMapping(outputMapping);
 
     QFile fstOutputFile { outputFSTURL };

libraries/baking/src/ModelBaker.h

@@ -82,6 +82,7 @@ protected slots:
     void handleFinishedMaterialBaker();
 
 private:
+    void outputUnbakedFST();
     void outputBakedFST();
 
     bool _hasBeenBaked { false };

libraries/fbx/src/FSTReader.h

@@ -33,6 +33,7 @@ static const QString BLENDSHAPE_FIELD = "bs";
 static const QString SCRIPT_FIELD = "script";
 static const QString JOINT_NAME_MAPPING_FIELD = "jointMap";
 static const QString MATERIAL_MAPPING_FIELD = "materialMap";
+static const QString COMMENT_FIELD = "comment";
 
 class FSTReader {
 public: