diff --git a/tools/sandbox/rhino3dm_error/rhino3dm_error.js b/tools/sandbox/rhino3dm_error/rhino3dm_error.js
index 10b6450..2caacfe 100644
--- a/tools/sandbox/rhino3dm_error/rhino3dm_error.js
+++ b/tools/sandbox/rhino3dm_error/rhino3dm_error.js
@@ -2,46 +2,40 @@ let rhino3dm = require ('../../../libs/rhino3dm.min.js')
 let fs = require ('fs');
 let path = require ('path');
 
-function Write3dmFileToJson (rhino, rhinoFileName, outputFolder)
+function GetThreeMeshesFrom3dm (rhino, rhinoFileName)
 {
-	console.log ('Writing 3dm to json: ' + outputFolder);
-	if (!fs.existsSync (outputFolder)){
-		fs.mkdirSync (outputFolder);
-	}
 	let inputBuffer = fs.readFileSync (rhinoFileName, null).buffer;
 	let inputArray = new Uint8Array (inputBuffer);
 	let inputDoc = rhino.File3dm.fromByteArray (inputArray);
 	let objects = inputDoc.objects ();
+	let threeMeshes = [];
 	for (let i = 0; i < objects.count; i++) {
 		let mesh = objects.get (i).geometry ();
 		if (mesh instanceof rhino.Mesh) {
-			let threeJson = mesh.toThreejsJSON ();
-			let jsonFileName = path.join (outputFolder, 'mesh' + i + '.json');
-			fs.writeFileSync (jsonFileName, JSON.stringify (threeJson, null, 4));
+			threeMeshes.push (mesh.toThreejsJSON ());
 		}
 	}
+	return threeMeshes;
 }
 
-function WriteJsonTo3dmFile (rhino, inputFolder)
+function WriteThreeMeshesTo3dm (rhino, threeMeshes, rhinoFileName)
 {
-	console.log ('Writing json to 3dm: ' + inputFolder);
 	let outputDoc = new rhino.File3dm ();
-	let fileNames = fs.readdirSync (inputFolder);
-	for (let i = 0; i < fileNames.length; i++) {
-		let fileName = fileNames[i];
-		if (path.extname (fileName) != '.json') {
-			continue;
-		}
-		let filePath = path.join (inputFolder, fileName);
-		let fileContent = fs.readFileSync (filePath);
-		let jsonContent = JSON.parse (fileContent);
-		let rhinoMesh = new rhino.Mesh.createFromThreejsJSON (jsonContent);
+	for (let i = 0; i < threeMeshes.length; i++) {
+		let rhinoMesh = new rhino.Mesh.createFromThreejsJSON (threeMeshes[i]);
 		outputDoc.objects ().add (rhinoMesh, null);
 	}
 	let writeOptions = new rhino.File3dmWriteOptions ();
 	writeOptions.version = 6;
 	let outputBuffer = outputDoc.toByteArray (writeOptions);
-	fs.writeFileSync (path.join (inputFolder, 'model.3dm'), outputBuffer);
+	fs.writeFileSync (rhinoFileName, outputBuffer);
+}
+
+function ReadWriteRhinoFile (rhinoIn, rhinoOut, inputRhinoFile, outputRhinoFile)
+{
+	let threeMeshes = GetThreeMeshesFrom3dm (rhinoIn, inputRhinoFile);
+	console.log ('Meshes in ' + inputRhinoFile + ': ' + threeMeshes.length);
+	WriteThreeMeshesTo3dm (rhinoOut, threeMeshes, outputRhinoFile);
 }
 
 if (!fs.existsSync ('output')){
@@ -49,14 +43,9 @@ if (!fs.existsSync ('output')){
 }
 
 rhino3dm ().then (async function (rhinoIn) {
-	Write3dmFileToJson (rhinoIn, 'input/hello_mesh.3dm', 'output/hello_mesh');
-	Write3dmFileToJson (rhinoIn, 'input/one_cube.3dm', 'output/one_cube');
-	Write3dmFileToJson (rhinoIn, 'input/two_cubes.3dm', 'output/two_cubes');
-	Write3dmFileToJson (rhinoIn, 'input/three_cubes.3dm', 'output/three_cubes');
 	rhino3dm ().then (async function (rhinoOut) {
-		WriteJsonTo3dmFile (rhinoOut, 'output/hello_mesh');
-		WriteJsonTo3dmFile (rhinoOut, 'output/one_cube');
-		WriteJsonTo3dmFile (rhinoOut, 'output/two_cubes');
-		WriteJsonTo3dmFile (rhinoOut, 'output/three_cubes');
+		ReadWriteRhinoFile (rhinoIn, rhinoOut, 'input/one_cube.3dm', 'output/one_cube.3dm');
+		ReadWriteRhinoFile (rhinoIn, rhinoOut, 'input/two_cubes.3dm', 'output/two_cubes.3dm');
+		ReadWriteRhinoFile (rhinoIn, rhinoOut, 'input/three_cubes.3dm', 'output/three_cubes.3dm');
 	});
 });