NVIDIA Flow or VecFlow's own solver
Smoke and fire can be worked by VecFlow's own gas solver or by NVIDIA Flow: what each is good at, and what changes when you switch.
Smoke and fire can be worked by either of two solvers. Pick one in the Smoke and Fire panel's Solver. The particles, the Smoke Sources and the panel's gas settings stay the same; so does the volume the bake makes, and how it plays and renders.
In short
| VecFlow (the default) | NVIDIA Flow | |
|---|---|---|
| Runs on | The CPU, or an NVIDIA card | An NVIDIA card only, on Windows and Linux |
| Results | The same on any computer, CPU or GPU | Depend on the card |
| Colliders | Goes closely round them | Goes round them less closely |
| Turbulence | Yes | No |
| State saves | Yes: bakes carry on and re-bake from a frame | No |
When to pick NVIDIA Flow
For big, loose gas where speed matters most and exactness doesn't: a large cloud of smoke, an explosion in the open, quick versions of a shot while you work it out. It's NVIDIA's real-time gas solver, built for speed.
When to stay with VecFlow's
- The gas must go round things closely: smoke curling round a statue, through a doorway, under a table.
- The shot needs Turbulence.
- You want to carry a bake on from a state save, or re-bake from a frame.
- The same result on every computer: a render farm, a team, or baking on the CPU on a Mac.
Switching
In the Smoke and Fire panel, set Solver to NVIDIA Flow.
Under Solver Quality, set Steps a Frame: how many steps Flow takes a frame. More follows fast gas better, and is slower. VecFlow's own Step Size, Most Substeps, Most Rounds and Accuracy don't apply to it.
Bake. Flow runs on the card the simulation's GPU setting picks.
If Flow can't run, the bake stops and says why: on a Mac, “NVIDIA Flow runs on Windows and Linux, not on this computer”; with no card it can use, “NVIDIA Flow can't run here: NVIDIA Flow sees no graphics card”. On a Windows laptop with two graphics cards, have Windows run Blender on the NVIDIA one (Settings > System > Display > Graphics, Blender, High performance).
What changes
- Colliders: Flow keeps their cells clear of gas and moving with them, but takes them as still air rather than walls, so gas passes closer and can seep round thin ones.
- Turbulence settings are ignored.
- Swirl: Flow takes Swirl, scaled by how fast the gas goes as Flow does it, and Swirl's In Heat, In Fuel, In Smoke and In Flame. It ignores the plume's Front, Back, Edge Lift and Edge Swirl, and the Disturbance.
- Sharpness sets how much of its sharpening Flow keeps: Fast is Flow's own, and Sharp and Extreme keep more.
- Fire: Ignition Range, Needs Air, Heat Spread, Flame Cutoff, Burn Limit, Soot Below Heat and Shrink are VecFlow's own, and Flow ignores them.
- No state saves: a Flow bake always runs from the start. Continue and Re-bake From aren't there for it.
- Results differ by card: two machines, or two cards, give slightly different gas. Bake the final on one.
Related
Fire and explosions
Flames off a burner or a mesh, and fireballs that swell and rise: fuel and how it burns, the flame's look, and the Fire and Explosion starters taken apart.
Moving and deforming emitters and colliders
Emitters, colliders and other objects that move, turn and change shape: what the bake follows, Inherit Motion, moving walls, and what marks a bake old.