System Summary #
The foliage physics system works through a chain of custom assets and blueprint systems, which can be seen in the flowchart below:
The Foliage Map acts as a reference library which stores the foliage static meshes and their associated blueprints, so that the system knows what blueprints to swap the meshes with.
A Foliage Influencer is an actor which detects nearby foliages instances in the level.
A Foliage Instance is simply a foliage mesh which has been painted by the foliage tool.
When the Foliage Influencer detects a Foliage Instance, it converts it to the associated blueprint listed in the Foliage Map asset.
Once a Foliage Instance has been converted to a Foliage Blueprint, the custom logic inside the Foliage Blueprint will determine when and how it turns back into a Foliage Instance.
In Unreal Engine, spawning and destroying many blueprints very quickly is bad for performance. The Object Pool is a hidden collection of objects that are created at the start of the game.
We keep Foliage Blueprints in the pool until they are needed, and return them to the pool when they are not needed.
Foliage Map #
A Foliage Map is a collection of all the foliage types you want to interact with physics.
It links each Foliage Blueprint to the Static Mesh you will paint with the foliage tool.
Each project requires at least one Foliage Map asset, but you can add more if needed.
Having multiple Foliage Maps can be useful when importing various foliage-physics environments from our Etherion Designs store.
You can create a Foliage Map by right clicking an empty space in the content browser, and going to Miscellaneous > Foliage Map.
You can also find an example Foliage Map in this location:
AlienPhysicsWorld / FoliageTypes / FoliageMap_DemoWorld
If you opWhen you open a Foliage Map, you’ll see two columns.
Each row corresponds to a foliage type, linking its Foliage Blueprint with a matching Static Mesh.
Automatic Fill #
To quickly fill your Foliage Map with all the foliage Static Meshes and their associated Foliage Blueprints, you can use these automated buttons:
- Global Auto-Fill: Searches for foliage meshes and blueprints throughout the entire project.
- Relative Auto-Fill: Searches for foliage meshes and blueprints only in the same folder as the Foliage Map.
The Auto-Fill buttons automatically find all blueprints that are children of BP_FoliageParent and read their StaticMesh component into the correct slot. Be sure to save your project before using these buttons, as they can sometimes malfunction.
Manual Fill #
To manually add foliage to your Foliage Map, click the + icon to create a new entry in the list.
Then, assign the Static Mesh on the right and its corresponding blueprint on the left.
Foliage Influencer #
A Foliage Influencer is a simple spherical actor that converts instances to blueprints.
When the a foliage influencer touches a Foliage Instance in your level, it instantly swaps the instance with the corresponding Foliage Blueprint listed in the Foliage Map. This conversion happens so fast that it creates the illusion that the foliage is always interactive.
The Foliage Influencer is highly optimized, allowing you to use virtually unlimited Foliage Influencers without noticeable performance impact.
Adding to your Blueprint #
To add a foliage influencer to your Character pawn or object, first open your Character Blueprint in a seperate window.
Then, navigate to AlienPhysicsWorld / FoliageSystem and drag BP_FoliageInfluencer into your blueprint.
Ensure Correct Attachment #
Next, please adjust BP_FoliageInfluencer in the blueprint hierarchy to ensure that it is attached to the object you would like it to move with.
Some examples might include:
- Player Pawn: Attach BP_FoliageInfluencer to your character mesh, or root Capsule Component.
- Vehicle: Attach BP_FoliageInfluencer to your Vehicle Mesh.
- Simulated Static Mesh blueprint: Attach BP_FoliageInfluencer to your Simulated StaticMesh.
- Simulated Skeletal Mesh blueprint: You can position your BP_FoliageInfluencer and attach it to your bone socket using a Construction Script.
Influencer Radius #
With BP_FoliageInfluencer selected,
go to the Details Panel and expand these tabs:
Child Actor Component > Child Actor Template > Foliage Influencer
Check the “Debug” checkbox to enable radius visibility.
With the sphere visible, you should adjust the radius until it covers the desired area.
Optimization #
To improve performance, it’s better to use multiple, smaller ‘Foliage Influencer’ actors than one large one.
This is because simulated foliage can be heavy on the CPU.
By using smaller influencers, only the foliage near your character or simulated objects will be activated, saving processing power.
Feel free to duplicate the BP_FoliageInfluencer component as many times as needed to cover your entire mesh area.
To further improve performance, you may want to change the Activation Type.
The Activation type determines when the Foliage Influencer is active.
You may want it to only be active when within view, within range, or when it is both within view and within a designated range.
If you set Activation Type to involve range, you can set the range using Activation Range variable.
This uses standard unreal units, and is measured as a distance from the camera.
Lastly, the Conversion Limit is an integer specifying the maximum number of foliage instances that this influencer can convert per-frame.
If you encounter larger framerate drops (especially when using a Foliage Influencer on projectile explosions), you may want to adjust this value so that it limits the amount of conversions.
Mesh Collision Settings #
Now lets configure the player’s or game-object’s mesh to ensure that it collides correctly with the simulated physics foliage.
With your blueprint open, select your character’s or object’s mesh and go to the details panel. Then scroll down to the Collision tab.
Ensure that Generate Overlap Events is checked.
Under the Collision Enabled dropdown box, your mesh must set to either of these options:
- Physics Only (No Query Collision)
- Collision Enabled (Query and Physics)
Under the Object Type dropdown box, the Character’s mesh should be assigned one of the following options:
- World Dynamic
- World Static
- Vehicle
- Destructible
By default, we recommend World Dynamic.
Finally, under the Object Responses section,
you must ensure that the Mesh has the Physics Body response set to Block.
Chaos Vehicle Collision Settings #
If the Blueprint you are working on is a Chaos Vehicle, you may notice some issues with the wheels bouncing all over your foliage.
This is because the Wheel utilises a line trace, and by default, it is set to hit PhysicsBody’s.
To fix this, select the Vehicle Movement Component.
In the Details Panel, scroll to Custom > Wheel Trace Collision Responses.
Change the response to PhysicsBody to Ignore.
The other collision settings should be similar to the character.
The only difference being that the Object type should typically be set to Vehicle.