Compute: CPU and GPU
Where a bake runs, on the CPU or an NVIDIA graphics card, what the GPU needs, and what to do when a bake says it ran on the CPU.
Every simulation bakes on the CPU. On Windows and Linux, it can also bake on an NVIDIA graphics card, which is much faster for big simulations. The result is the same either way, so you can work out a look on one computer and bake the final on another.
Compute
Compute is the first setting in Bake Settings:
| Choice | Bakes |
|---|---|
| Auto (the default) | On the GPU when there's one and the simulation can run there; otherwise on the CPU, and says why |
| GPU Only | On the GPU or not at all: a simulation that can't run there doesn't bake, and says why. For when a slow CPU bake by mistake would cost you hours |
| CPU | On the CPU |
Where Compute isn't CPU and there's no GPU to use, Bake Settings says why under the setting.
What the GPU needs
- An NVIDIA RTX 20 series or newer, or a GTX 16 series card.
- An NVIDIA driver of the 580 series or newer.
- Windows or Linux. A Mac bakes on the CPU.
AMD and Intel graphics cards aren't used. See Requirements.
Where it ran
After a bake, the status box says where it ran:
- "Ran on the NVIDIA GeForce RTX 4070 in 1 min": on that card.
- "…; on 2 cards (…)": a big liquid or smoke solved over several cards. See More than one GPU.
- "…; surface on the CPU" or "…; surface on the GPU": where the liquid's surface was meshed, when that wasn't beside the solve.
- "Ran on the CPU: reason": Compute was Auto, and the GPU couldn't take it.
- "Ran on the CPU: the GPU failed (reason), so the bake started again there": see below.
Why a bake runs on the CPU
| Reason | What to do |
|---|---|
| GPU baking needs an NVIDIA card, on Windows or Linux: a Mac bakes on the CPU | Nothing: this computer bakes on the CPU |
| This machine has no NVIDIA GPU / No NVIDIA driver found | Install the NVIDIA driver, if there's an NVIDIA card |
| The NVIDIA driver is too old for VecFlow's GPU code… | Update the driver to the 580 series or newer |
| GPU is older than the RTX 20 series, which VecFlow's GPU code needs | The card is too old; bake on the CPU |
| The GPU ran out of memory | The simulation is too big for the card. Spread it over more cards, or lower the detail |
| Too many particles for the GPU | As above |
| 'event' has more than 8 grounds, too many for the GPU | More than eight Collide operators with Ground in one event. Use fewer |
| A liquid's colliders, more than 32 of them, are too many for the GPU | Join some colliders into one object |
Messages lists every message, with these.
When the GPU fails mid-bake
On Auto, if the GPU fails partway (out of memory, a driver error), the bake starts again from the beginning on the CPU, once, and the status says so. On GPU Only, the bake stops with the reason.
NVIDIA Flow
The Smoke and Fire panel's Solver can be NVIDIA Flow: NVIDIA's real-time gas solver, on a graphics card, Windows and Linux only. It's fast, but its result depends on the card, it goes round colliders less closely, has no turbulence, and makes no state saves. VecFlow's own solver runs on the CPU or the GPU with the same result either way.