Volumetric Fire Forge is a WebGPU-only reactive-fire laboratory built on
VolumetricFireSimulation. The
simulation advances velocity, pressure, fuel, heat, and smoke in fixed 1/60-second increments for
stable numerical behavior across ordinary frame-rate variation. A bounded accumulator limits
catch-up work after a slow frame, while pause, single-step, reset, and time-scale controls make the
solver's evolution directly inspectable.
The visible hearth, walls, lips, and burners come from the same authored box list used to voxelize the simulation's obstacle texture. That shared geometry keeps the collision mask aligned with the forge surfaces instead of relying on two independently maintained scene descriptions. The solver and renderer record their work in order on the frame's caller-owned command encoder, without CPU readback or a hidden submission between simulation and display.
The volume compositor reconstructs opaque scene depth, intersects each camera ray with the fire bounds, and stops integration at the first forge surface. Front-to-back Beer-Lambert extinction combines smoke absorption with self-shadowed scattering, while the combustion texture drives heat-shaped HDR emission with a bounded ember-to-gold palette. The result remains linear in a floating-point HDR target through multiscale bloom and the final tone map.
Fire is intentionally presented with Fixed Exposure. Fast changes in flame area therefore do not pump the brightness of the entire forge, and the bloom threshold, intensity, and radius expose highlight shaping independently from the simulation. On compatible displays, the example requests an extended-range canvas; other displays receive the same fixed-exposure filmic composition in SDR.
Each burner occasionally receives a deterministic, irregular flare that boosts its real fuel, temperature, density, source radius, and upward impulse. The same envelope raises that burner's HDR radiance and local brick-and-floor spill, so the effect is not a screen-space flash. Click a visible flame to trigger its flare directly. A short click is distinguished from an orbit drag, and the nearest projected burner must be inside the click radius. After the first pointer or keyboard interaction unlocks browser audio, flares also produce a synthesized, distance-attenuated low combustion whoomph; use Mute sound to disable it.
What to inspect
- Drag to orbit, use the wheel or trackpad to zoom, toggle Auto Orbit, or reset the camera.
- Click an individual flame to trigger its volumetric HDR flare. Click empty space or drag across a burner to verify that those gestures do not fire one.
- Compare the Foundry, Blast Furnace, and Smolder presets, then adjust buoyancy, turbulence, reaction rate, time scale, and voxel quality.
- Pause and use Single step to inspect one fixed simulation update at a time, or reset the fire after changing its preset or dynamics.
- Tune ray samples, smoke absorption, HDR emission, smoke lighting, and self-shadow strength to separate transport behavior from volume-rendering choices.
- Switch from Final to density, temperature, fuel, age, velocity, obstacle, or transmittance views. These diagnostics sample the live GPU textures; they do not stage the volume through the CPU.
- Watch the inspector for volume dimensions, voxel count, solver steps, GPU graph-node count, and the active scene color format.