Creating Open-World Grass Clutter with SpeedTree

Junichiro Ishino
Graphic Designer

Published: Dec. 03, 2025

Introduction

This explains an asset-creation workflow using SpeedTree.
Since we will place large quantities of grass in an open-world environment, the assets must be as light as possible.

Tech demo

How it moves in UE

Play

On WindDirectionalSource

LOD transition with UE

Play

Add Transition to the material to create a smooth LOD transition.

How the Clutter fits the ground

Play

Explanation

Search for assets on Quixel

We will use fbx mesh files and textures.

Create fbx using a DCC tool

Import the FBX-format mesh and adjust its density.
Keep the entire mesh within a manageable triangle count.
Export the fbx.

Render Texture for the Cluster in SpeedTree

Import the fbx mesh you just created, along with Quixel textures, to prepare data for the cluster.
Export the texture that will be used as the card mesh.

Create the Final Asset in SpeedTree

Create nodes in SpeedTree and import the cluster texture you created earlier. This will become the final asset you export to Unreal Engine.

To simulate wind movement, connect Spline → Cluster nodes.
Do not use Leaf nodes.

Cut out the mesh based on the texture

Wind

Launch the Wind Wizard and set it to Bush.

Spline › Animation › Wind
enable Apply under Legacy UE4.

The Wind settings that we used

Set Up LOD

Create “4 mesh LOD” + a far-distance billboard

Export the .st File

Import into Unreal Engine

LOD: 0

LOD: 1

LOD: 2

LOD: 3

LOD: 4

This asset will be used as grass clutter to be placed widely across the map.
To reduce the number of placed instances, make each asset fairly large (around 5.5 meters in size)
Use HeightMap so it fits to the ground.

Enable Accurate Wind Velocities in the SpeedTree asset settings to reduce noise caused by wind movement.