Flux Emanation

Challenge

The goal was to make the laser feel like part of the simulation rather than a separate effect. The physical beam and rendered fluid needed to move together convincingly, as though the laser were acting inside the same virtual volume.

Architecture

Flux Emanation runs across two computers. A rendering computer runs Unreal Engine 5 and handles the scene, the fluid simulation, lighting, and rendering. A control computer runs TouchDesigner as the show controller, sequencing a timeline of fluid presets, colors, and lighting values. Parameter data travels to Unreal over OSC and textures over NDI, and Unreal streams its rendered frames back across the network, where TouchDesigner performs the projection mapping and laser output. Splitting the system kept the heavy simulation and rendering workload on its own machine and made iteration fast during development, since adjustments made in TouchDesigner update the Unreal scene immediately.

I presented a full breakdown of this architecture at the Austin TouchDesigner meetup in September 2025.

The Fluid Simulation

I built the simulation with Niagara Fluids, the VFX system native to Unreal Engine 5, which pairs a grid solver for the body of the fluid with particles for spray and detail. To understand the methods underneath it, I studied Robert Bridson’s Fluid Simulation for Computer Graphics, the standard text on the numerical methods behind film and game fluids. That research later carried into the custom SPH simulation for The Midnight Zone.

Unreal’s lighting was a major reason for choosing it. Lumen provides real-time global illumination, and emissive materials let individual fluid particles radiate light into the scene. Select particles in the simulation carry emissive materials, so the fluid appears to absorb the laser’s energy and holds a subtle glow after the beam moves on.

Laser Mapping

Select glowing particles in the fluid become targets for physical laser beams. TouchDesigner derives those targets from the final rendered image, keeping the laser synchronized with what the audience sees. A calibration pass aligns the laser field with the projection so both outputs remain locked to the same scene.