Blender Procedural, a prolific developer of procedural tools for Blender, has released Fluid Flow, a real-time multiphysics add-on built entirely on Geometry Nodes. The add-on allows artists to paint water, lava, or sand into a scene, watching the materials respond under gravity directly in the viewport. Unlike conventional simulation solvers, Fluid Flow operates interactively: once set up, pressing Play produces instant results, without caching or baking. At a price of $14, Fluid Flow positions itself as a lightweight creative utility for motion graphics, concept animation, and other stylised or non-photorealistic projects. It is compatible with Blender 4.2 or newer.
Painting materials that move
Fluid Flow’s operation begins with a simple panel inside Blender’s sidebar. The core parameter, Simulation Type, toggles between Water, Lava, and Sand modes, each of which defines distinct physical behaviour. Creating a new simulation automatically generates a domain grid—usually a plane—and assigns it as the simulation area. Artists can add collision meshes (such as terrain, rocks, or walls) via Add Collision to Active Object. Without at least one collision mesh, the simulation will not appear outside the collider surface, a key technical note emphasised in the official documentation. The add-on uses a domain-emitter architecture: the domain represents the computational grid, while an emitter injects the chosen material. Once an emitter and collision setup are defined, playback triggers the physics solver.
Technical controls: from domain size to cooling rates
The configuration panel exposes several core and per-mode settings, all operating within Blender’s node-based framework. Users can specify the Collision Collection, domain dimensions (Size X/Y), and grid resolution (Vertices X/Y). The Speed parameter controls global flow velocity, while Solver Iterations affect per-frame stability and definition. Increasing iterations or enabling Blur Iterations can stabilise granular materials or smooth out minor jitter.
The Emit Factor slider multiplies emission strength, offering rapid control over fluid volume. The Scale parameter modifies internal gravitational scaling, helping to adjust for unusual scene scales.
For each material mode, Fluid Flow adds targeted physical parameters:
- Sand: uses a Slope Angle (angle of repose). Below the angle, sand accumulates; above it, it slides. Typical stable ranges are 32–38°.
- Lava: includes Cool Rate and Heat Radius controls. Cooling defines how quickly the lava solidifies; heat radius determines how far thermal influence extends around the emitter.
- Water: behaves as a flowing liquid layer that seeks the lowest point in the domain.
Each simulation type supports unique materials and shaders: transparent and refractive water with foam; emissive lava with a solid crust; rough, granular sand with physically-based scattering.
From stylised dunes to cooling lava flows
Fluid Flow’s focus is interaction over precision. Rather than solving the full Navier-Stokes equations as FLIP-based or SPH solvers do, it approximates fluid motion via procedural field operations inside Geometry Nodes. The result is a system that behaves believably, if not physically, and runs directly in the viewport. Sand forms heaps and slides dynamically, lava thickens and cools, and water flows downhill along any sculpted mesh terrain.
This makes Fluid Flow a useful concept tool: for example, blocking in stylised dunes, riverbeds, or fantasy lava channels without leaving the modelling environment. Unlike FLIP Fluids or Cell Fluids, Fluid Flow does not attempt sub-surface pressure modelling or viscosity control beyond basic flow speed. Its goal is to “feel right” visually, not to match real-world fluid behaviour.
Quick start workflow
The workflow prioritises simplicity:
- Click Create New Simulation to initialise a domain.
- Add terrain or other geometry as colliders using Add Collision to Active Object.
- Choose a mode under Simulation Type (Water, Lava, or Sand).
- Assign an Emitter Object.
- Press Play to begin simulation and tweak Speed, Emit Factor, or material-specific parameters live.
A recommended starting setup is a 50-metre domain with 200×200 vertices, allowing stable playback before increasing resolution. The documentation stresses scale consistency: mismatched scene units can cause unstable or sluggish behaviour.
When instability or jitter occurs, raising Solver Iterations, enabling Blur Iterations, or slightly lowering resolution tends to restore stability.
Materials and shading integration
Each mode supports a dedicated material system that can drive visual effects via attribute masks. The lava shader, for example, uses emission intensity and cooling maps to simulate crust formation, while the sand material responds to slope and height attributes.
Artists can assign any compatible shader to the Material slot in the panel. The documentation provides presets for transparent water, rough sand, and emissive lava, all of which can be extended through standard Blender node networks. These materials are procedural and fully viewport-visible, giving immediate feedback during layout or concept stages.
Stability and troubleshooting
While the add-on operates in real time, the developer outlines several known limitations:
If no simulation appears, the terrain may not be marked as a collider or assigned to the correct collision collection.
If sand behaves like water, the Slope Angle is likely too low, or the flow speed too high.
If lava freezes immediately, lower the Cool Rate; if it never cools, increase it slightly.
Solver instability can occur at very high resolutions or with extreme scaling. Increasing iteration counts generally mitigates such issues.
Not a fluid solver, but a painter’s tool
Fluid Flow’s charm lies in its immediacy. It functions less as a simulation engine and more as a procedural painting system for motion and terrain effects. It is particularly useful for motion design, concept visualisation, and pre-viz: areas where iteration speed outweighs physical fidelity. For production VFX pipelines requiring physically correct viscosity, surface tension, or particle-mesh coupling, dedicated solvers such as FLIP Fluids remain indispensable. Still, Fluid Flow’s ability to sketch ideas interactively, without baking or waiting for caches, represents a meaningful workflow convenience for artists operating in stylised or abstract visual contexts.
Compatibility and price
Fluid Flow supports Blender 4.2+ and is available through the Superhive marketplace for USD 14. The add-on installs as a standard .zip package and loads under Blender’s “Add-ons” preferences. Because it uses only Geometry Nodes and standard shader attributes, it runs entirely on the GPU, with performance depending on viewport complexity rather than solver type.
Production considerations
As with all viewport-based solvers, users should validate results before committing them to final rendering or compositing. Viewport shading, adaptive tessellation, and anti-aliasing can all affect how simulation edges appear, particularly for emissive lava materials.
Conclusion
Fluid Flow distils the essence of real-time physics into an approachable Geometry Nodes framework. It will not replace full solvers, but it might replace several hours of setup and caching in concept and pre-visualisation tasks. For Blender artists seeking to draw motion rather than calculate it, Fluid Flow offers a rare combination of immediacy, control, and procedural logic, all for the price of a takeaway meal. As always: test before you trust.
