# Example - Mesh Export
The following C# program connects to a Voxel Farm server and exports the terrain surface within a 3D region as a mesh:
```c#
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using VoxelFarm;
namespace ExportMesh
{
class Program
{
private static void Terrain2MeshOBJ(
string webServer,
string contentServerAddr,
int contentServerPort,
string projectId,
string entityId,
Region25D region,
int lod,
string outputFile)
{
// Create output file
System.IO.StreamWriter fileOutput = new StreamWriter(outputFile);
// Local variables to track OBJ output
bool done = false;
int totalFaces = 0;
int vertexIndexOffset = 1;
// Start work pool
VoxelFarmWorkPool.Start(2 * Environment.ProcessorCount);
// Create view
VoxelFarmView view = new VoxelFarmView();
// Print view debug log
view.OnDebugLog = (message) =>
{
//Console.WriteLine(message);
};
// Also print any uncaught error
VoxelFarmWorkPool.OnError = (Exception error) =>
{
Console.WriteLine(error.Message + " " + error.StackTrace);
done = true;
};
// Set OnViewStarted event
view.OnViewStarted = () =>
{
try
{
// Use the supplied region to create a set of ranges of 10x10x10 cells
var ranges = region.breakdownRegion(lod, 10, view.AffineTransform);
// Iterate over each range of cells
int totalRanges = ranges.Count;
int completedRanges = 0;
foreach (var range in ranges)
{
// Output progress message
int progress = (100 * completedRanges++) / totalRanges;
string message = (totalFaces > 0) ? String.Format("{0:0,0} triangles exported...", totalFaces) : "Scanning for triangles...";
Console.WriteLine(progress + "% " + message);
// Ask the view to load the cell range
view.SetCellRange(range);
// Wait until the view completes processing the range
view.Join();
// Check that we still have a connection to the server
if (view.ConnectionLost() || !view.IsConnected())
{
Console.WriteLine("Lost connection to content server.");
done = true;
}
}
done = true;
}
catch (Exception error)
{
Console.WriteLine(error.Message + " " + error.StackTrace);
done = true;
}
};
// Define a callaback to handle mesh data
view.OnReceiveMeshData = (data) =>
{
ManualResetEvent outputDone = new ManualResetEvent(false);
VoxelFarmWorkPool.RunInMainThread(() => {
int level, xc, yc, zc;
VoxelFarmCell.Unpack(data.cellId, out level, out xc, out yc, out zc);
double scale = VoxelFarmConstant.CELL_SIZE * (1 << level);
double cellOffsetX = scale * xc;
double cellOffsetY = scale * yc;
double cellOffsetZ = scale * zc;
int vertCount = data.vertices.Length / 3;
int faceCount = data.faces.Length / 3;
for (int i = 0; i < vertCount; i++)
{
var wc = view.AffineTransform.VF_TO_WC(
new VoxelFarmAffineTransform.sAffineVector
{
X = data.vertices[3 * i + 0] * scale + cellOffsetX,
Y = data.vertices[3 * i + 1] * scale + cellOffsetY,
Z = data.vertices[3 * i + 2] * scale + cellOffsetZ
});
fileOutput.WriteLine("v " + (-wc.X) + " " + wc.Z + " " + wc.Y);
}
for (int i = 0; i < faceCount; i++)
{
fileOutput.WriteLine("f " +
(data.faces[3 * i + 0] + vertexIndexOffset) + " " +
(data.faces[3 * i + 1] + vertexIndexOffset) + " " +
(data.faces[3 * i + 2] + vertexIndexOffset));
}
vertexIndexOffset += vertCount;
totalFaces += faceCount;
outputDone.Set();
});
outputDone.WaitOne();
};
// Set server and project
view.SetServer(webServer, contentServerAddr, contentServerPort, false);
view.SetProjectId(projectId);
// Load the project
view.LoadProject((HttpStatusCode httpcode) =>
{
if (httpcode == HttpStatusCode.OK)
{
// Find entity
var terrainEntity = view.GetEntity(entityId);
if (terrainEntity == null || terrainEntity["file_type"] != VoxelFarmEntityType.VoxelTerrain)
{
done = true;
return;
}
// Create view metadata
var components = new List();
var componentMasks = new List();
List layerStack = new List();
layerStack.Add(new VoxelFarmMetaLayerHM { Id = entityId, Config = terrainEntity["runtime"] });
var layers = new VoxelFarmMetaLayerStack(layerStack);
var surface = new VoxelFarmMetaSurfaceOperation { OpId = VoxelFarmMetaID.META_OP_NONE, OpA = layers };
components.Add(surface);
componentMasks.Add(0x02);
var componentMaterials = new List();
componentMaterials.Add(0xFFFF);
var metadata = new VoxelFarmViewMeta(components, componentMasks, componentMaterials, null);
// Set view metadata, this will start the connection to the streaming server
view.SetViewMetaData(metadata);
}
else
{
done = true;
}
});
while (!done)
{
VoxelFarmWorkPool.RunNextMainThreadJob();
}
fileOutput.Close();
VoxelFarmWorkPool.Stop();
Console.WriteLine("Export complete.");
}
static void Main(string[] args)
{
if (args.Length != 8)
{
Console.WriteLine("Usage ExportMesh.exe