#### grid solver

This is the voxel grid solver.

[Inputs]

Enabled - Enable or disable node evaluation.

Grid - Select available grid from the list. Any voxel simulation requires at least one of the nodes - FumeFX Simulation Ref or Initialize Grid node.

Solver Quality - This parameter defines the simulation realism. Higher quality increases realism at the cost of increased computation and slower simulation performance. It is advisable to increase quality for fast moving objects.

Maximum Iterations - This parameter sets the maximum number of iterations the solver can complete. If not bounded by this parameter, the solver will automatically stop when it reaches an acceptable level of accuracy defined with Solver Quality parameter. The solver does not need many iterations to achieve good results (20-30 for small grids, 100 for bigger grids, or fast sources/objects).

CFL Condition - This value defines the maximum distance allowed for any cell data (velocity, smoke, fire, etc..) to travel in one simulation step. This number has a direct influence on the number of Simulation Steps. For example, if you use the CFL number 5, it would mean that if the system detects any velocity inside the voxel grid that will result in a field to travel more than 5 voxels in one simulation step, the simulation step will be divided so that the distance does not exceed this number. Generally, simulation is stable when CFL number is kept between 4 and 5, unless you notice artifacts, much bigger values can be used as well. If you choose values too small you can expect the

effect of blurring.

You have to keep in mind that by decreasing the Spacing value you actually decrease voxel dimensions. This will result in increase of simulation steps required to satisfy the CFL Condition, because velocities will be able to carry cell data through to more voxels.

It is not always an imperative to have many simulation steps as fluid motion can look convincing even with one. You always need to find the balance between simulation time and "mathematical correctness" of the simulation.

Minimum Simulation Steps - This parameter will set the minimum number of simulation steps, regardless of the CFL Condition value.

Maximum Simulation Steps - The number of steps is directly controlled through CFL Condition parameter value, but with this parameter, you can limit maximum number of steps.