Blaze overview

Blaze is the smoke, fire and explosion solver. A Blaze graph is a Blaze Solver wired into Simulation Output, with emitters, forces, colliders and three satellite nodes around it. Everything is in SI units, and the same values drive the viewport preview and the render.

The quickest start is a template from the Blaze group, or Quick Smoke and Fire on a mesh.

Units

Quantity	Unit	Notes
Length, voxel size, domain	metre	The domain box is in world space. A Domain Object’s bounding box replaces the Size.
Temperature	kelvin	Emitter temperature, ignition and ambient (293 K is 20 °C). Heat is measured from the ambient.
Temperature change	kelvin	Flame Heat (per unit of fuel burned) and the mask thresholds.
Speed	m/s	Emitter velocity, wind, shred speed.
Acceleration	m/s²	Gravity, turbulence strength, disturbance, swirl.
Buoyancy	m/s² per 1000 K	Scales with the Gravity force. Real hot gas lifts at about g·ΔT/T (about 33 per 1000 K). The templates use 2 to 12.
Rates	1/s	Burn rate, cooling, dissipation and drag.

The graph

Blaze Emitter ─┐
Forces ────────┼─► Blaze Solver ─► Simulation Output ◄─ Blaze Look
Colliders ─────┤        ▲
               │   Combustion, Dissipation, Detail (satellites)

• Sources, forces and colliders
• Combustion, dissipation and detail
• Bake, upres and checkpoints
• Performance
• Blaze Look for shading

The domain box

Note

The domain box is the edge of the simulation. The sparse backend only spends memory and time where there is gas, in bricks of 8×8×8 cells. It does not grow the box. Gas that reaches an open face leaves the simulation, and gas against a closed face is cut flat there.

Size the box for the whole shot: a mushroom cloud’s height, a smoke trail’s length. The empty part of the box costs almost nothing.

Blaze Solver settings

Setting	What it does
Voxel Size	The resolution. Halving it gives 8 times the cells where there is gas.
Size / Domain Object	The domain box. A Domain Object’s bounding box replaces Size.
Move With Object	The domain follows the Domain Object every frame, in whole bricks, keeping the gas where it is in the world. Use it for a carried torch or a vehicle’s trail. Sparse backend only.
Open Faces	Which of the six faces let gas leave and air in. A closed face is a wall. The floor (-Z) is closed by default.
Buoyancy, Smoke Weight	Upward acceleration per 1000 K of heat, and downward pull per unit smoke density.
Wind, Wind Drag	Ambient wind the gas is dragged toward, and how fast.
Ambient (K)	Air temperature. Heat is measured from it.
Time Scale	1.0 is real time at 24 fps.
Backend	How the lattice is stored on the GPU. Sparse is the default.
Multigrid Pressure Acceleration	A multigrid preconditioner for faster pressure projection. On by default.
Activity Threshold	Sparse backend: smoke, flame or fuel below this counts as empty air, so its bricks are freed.

The solver node also shows the cell count, GPU memory, bricks in use, first-run compile progress and any warning with a Fix button. See Solver warnings.

Every setting is listed in the Solver reference.

Live and bake

Live is the interactive preview and uses faster numerics. Bake uses higher-quality advection and writes OpenVDB frames. The smoke from the two agrees within about 10%. See Bake, upres and checkpoints.