Solver

The GAZ Solver node is structurally a wrapper around a standard DOP Network. In the default operating mode (combustion disabled), the node uses only the density, velocity, and temperature fields.

When combustion is enabled, memory is also allocated for fuel.

The node has five ports for connecting emitters, colliders, forces, and an active simulation zone limiter.

Each parameter on the node has its own inline help when hovering over it with the cursor.

Setup

Compute Device

At the moment, the simulation can only be computed on a single selected device.

Clear memory on start

The node does not pre-allocate a large chunk of memory, as some greedy GPU renderers do. However, by default, the used memory is retained after a restart. This option enables forced memory release.

Quality gradation

The simulation currently has two quality levels: balanced and high. At high quality, memory consumption increases significantly, with a substantial improvement in detail.

CFL

A condition ensuring that a gas does not move more than (this_value * tile_length) in a single time step. If the condition is violated, the time step is subdivided by two, continuing until the condition is no longer violated.

The default value is quite high and is suitable only for smoke. When combustion is enabled, it is recommended to lower it until “rubber-like” flame stretching disappears.

Values below 0.10-0.15 provide little to no quality improvement but cause excessive blurring of details.

Bounds

The simulation area can be limited by an object connected to the solver node’s bounds port. If the area is expected

to be almost always fully filled with visible gas, it is recommended to disable the Keep In Bounds setting to save time on inserting/removing tiles and extrapolating velocities into newly created ones.

The Soot/Fuel Sensitivity parameters act as a threshold below which a tile is removed.

DOP Playback Policy

Switches between interactive and caching modes for the DOP network. It also allows caching all computed and rendered frames in

the GAZ Viewer, regardless of the DOP mode, for fast playback or exporting a sequence of frames.

Forces

Directional

Forces acting in a straight direction. Note that wind differs from pushing in that it attempts to align the gas velocity and direction

with the specified parameters, whereas pushing represents an unconditional increment in velocity.

Drag reduces velocity proportionally to its magnitude, rapidly decreasing high speeds while having little effect on low speeds.

It is suitable for simulating air resistance, such as settling dust after an explosion.

Disturbance

Disturbance simulates the effect of small perturbations in the air, adding a random vector to the velocity field with a specified scale.

Vorticity

Vorticity detects existing vortices of a specified size and amplifies them. Note that, unlike most solvers, GAZ allows for enhancing

rotations at an explicitly defined scale, which can be useful in scenarios where handcrafted turbulence was previously applied via noise.

Turbulence

Standard curl noise, an artificial turbulence that is not inherently part of the simulation.

Thermodynamics

Air cooling

The rate at which gas cools down, nonlinear attenuation with a significant effect on emissive (fire, explosions) simulations.

Diffusion

Blurring of the corresponding field. Blurring velocity is equivalent to increasing viscosity.

Dissipation

A simple reduction of field values without any physical basis.

Burning

A simple model that linearly decreases the amount of fuel while increasing the amount of soot, temperature, and pressure for each voxel whose temperature is below the ignition temperature.

Fuel Burn Inefficiency

At a value of 0, fuel decreases strictly by the amount defined by the Burn Rate. At values >0, a portion of the fuel remains untouched,

without affecting the rest of combustion.

At a value of 1, all fuel remains untouched, but combustion still proceeds as usual.

Instability

Simulates fire flickering caused by oxygen starvation followed by fuel mixture saturation. To fully observe this effect,

temperature emission in sources should be disabled, allowing combustion to generate enough heat on its own

(it may be necessary to lower the ignition temperature).

Input/Output

The solver supports any VDBs (and polygons too) provided to the sources and collider ports. For optimal performance (but not very dramatically), the VDB resolution should match the solver voxel size.

For finer control over sourcing, it is recommended to insert a GAZ Source node in VDB mode between the solver and the VDB,

which also allows applying additional noise during VDB injection.

Input Naming

Uses wildcard syntax to define mappings between VDB fields and solver fields.

Output VDB

Outputs data from the solver to a VDB. Globally enabled/disabled via the Allow Output VDB toggle at the top of the node interface,

next to the Reset Simulation button.

GAZ View

For a detailed description of the parameters of this tab, please refer to the chapter Viewer.