Working with fluid simulation in Unity can often become a technical challenge, especially when you want water, lava, erosion, and terrain interaction to behave consistently in real-time. Heightmap-based systems can get you part of the way there, but getting something interactive, performant, and visually coherent usually requires a specialized tool.
Fluid Frenzy by Frenzy Byte, is a GPU-accelerated fluid simulation and renderer created to bring physically motivated 2.5D fluid behavior into Unity projects while supporting terrain interaction, terraforming, and multi-fluid mixing.
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What Is Fluid Frenzy and How It Works
Fluid Frenzy is a GPU-accelerated 2.5D fluid simulation system built on shallow water equations. It simulates fluids such as water and lava flowing across Unity Terrain, custom terrain systems, or any heightmap texture. The simulation responds to terrain height, obstacles, and modifiers that add or remove fluid, apply forces, or generate waves.
The system uses GPU solvers to update height, depth, and velocity fields in real-time. Optional GPU particles appear in cases like breaking waves or waterfalls, while a quadtree-based LOD system increases detail near the camera and reduces it at distance. Two fluid layers can run in the same simulation, supporting interactions such as water and lava forming rock.
A custom terraforming system lets the simulation modify terrain height and splat maps at runtime. Rigidbodies receive buoyancy and advection forces based on local fluid motion. Simulation data can be accessed in C# through the FluidSimulationManager to retrieve height, depth, velocity, or layer information, along with event triggers when fluid enters or leaves a position.
Samples, shaders, and interaction components are distributed through Unity’s Package Manager using the Hybrid Package workflow.
Main Features
- 2.5D Shallow Water Simulation: Fluid Frenzy uses shallow water equations to simulate wave behavior, flow, and height-based movement across a surface.
- Terrain Interaction: The simulation works with Unity Terrain, the custom Terraform Terrain system, or any heightmap-based terrain. Fluids follow slopes, fill depressions, and move around obstacles.
- Terraforming: The system includes real-time terrain modification, allowing fluids to erode and alter terrain layers. This can be used to create dynamic environments or god-game mechanics.
- Fluid Layer Mixing: Two fluid layers can interact and mix. Water and lava, for example, can combine to form rock on the terrain.
- GPU-Accelerated Rendering: A GPU-driven quadtree LOD system improves performance by focusing higher detail near the viewer while reducing cost elsewhere.
- GPU Particles: Optional GPU-accelerated particles can appear during events like breaking waves or waterfalls, interacting with the simulation.
- Obstacle Interaction: Objects in the scene can be marked as obstacles so fluids flow around or collide with them.
- Interaction Components: Modifiers can add or remove fluid, apply forces, or generate waves directly in the simulation.
- Water and Lava Rendering - Built-in shaders include features such as:
- Reflection
- Reflection
- Subsurface scattering
- Foam mapping
- Vertex displacement
- Emission and velocity-based heat (lava)
- C# Scripting Access: Developers can query fluid height, depth, velocity, and layers using the FluidSimulationManager and event triggers.
Use Cases
Fluid Frenzy can be used for:
- Dynamic rivers flowing over terrain.
- Lava systems with thermal behavior.
- Erosion-based environments and god-game mechanics.
- Water simulations for gameplay interaction.
- Prototyping terrain alteration systems.
- Stylized or realistic liquid rendering.
- Scenes that require runtime buoyancy or fluid-driven physics.
Limitations
According to the developer:
- This is a 2.5D shallow water equation simulation, meaning fluids can only flow over objects, not under them.
- Simulation speed has a maximum limit due to pixel-based movement.
- Multiplayer is not supported because network synchronization of fluid data is impractical.
- Best performance is achieved with Shader Model 5.0 on DirectX or Vulkan.
- WebGL 2 support is in beta and does not include GPU particles or steam.
If you’d like to explore more about Frenzy Byte’s work or follow updates, you can check out the pages below:
- X page: https://x.com/FluidFrenzy
- Fluid Frenzy page: https://assetstore.unity.com/packages/vfx/shaders/fluid-frenzy-273366
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