# Create Your Own Voxel Data Stream
You can provide your own stream of voxel data by extending VoxelStream either in GDScript or C++.

Note: Your stream must be thread safe.

Create MyStream.gd with the following contents:

```
extends VoxelStream
	
func emerge_block(buffer:VoxelBuffer, origin:Vector3, lod:int) -> void:
	if lod != 0: return
	if origin.y < 0: buffer.fill(1, 0)	
	if origin.x==origin.z and origin.y < 1: buffer.fill(1,0)
```

In your terrain generation script, add this:

```
const MyStream = preload ("MyStream.gd")
var terrain = VoxelTerrain.new()

func _ready():
	terrain.stream = MyStream.new()
	terrain.voxel_library = VoxelLibrary.new()	
	terrain.view_distance = 256	
	terrain.viewer_path = "/root/Spatial/Player"    # Set this path to your player/camera
	add_child(terrain)
```

<img src="images/custom-stream.jpg" width="800" />

Though `VoxelBuffer.fill()` is probably not what you want to use, the above is a quick example. Emerge_block generally gives you a block of 16x16x16 cubes to fill all at once, so you probably want to use `VoxelBuffer.set_voxel()` to specify each one.

In the fps_demo, there is a [custom gdscript stream](https://github.com/tinmanjuggernaut/voxelgame/blob/master/project/fps_demo/scripts/MyStream.gd) that makes a sine wave. This was copied from the [C++ version](../streams/voxel_stream_test.cpp), which runs a lot faster. 

<img src="images/custom-stream-sine.jpg" width="800" />



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