= How to |> speed up particle visualization and simulation =

== Minimize the level of detail in the viewport ==

# Press ((D)) in the viewport to launch the [Display options window|/ref/windows/displayopts_3d].

# On the __Viewport__ tab, turn down the __Level Of Detail__.

    For example, from 1 to 0.001.
    
    [Image:/images/shelf/particles_detail.png]
        
== Turn off guide geometry ==

In the [DOP Network|/nodes/obj/dopnet], turn off the __Show Guides Geometry__ checkbox on the __Guides__ tab of the [Particle Fluid Object|Node:DOP/particlefluidobject].

    You will still be able to see the particles.
    
    [Image:/images/shelf/particles.png]

== Increase the distance between particles ==

On the [Particle Fluid Object|Node:DOP/particlefluidobject], increase the __Particle Separation__ value.

    For example, from 0.1 to 0.25.
    
    [Image:/images/shelf/particles_separation.png]
    
== Use particle sinks ==

Using sinks ensures that you are only simulating the important particles, and not the ones that are off camera.

# Select the particle fluid to apply the sink to.

# Click the [Icon:DOP/particlefluidsink] [Sink Particle Fluid|/shelf/sinkparticlefluid] tool on the __Liquid__ tab of the shelf.

    You can use the handles to drag the purple bounding box around the viewport. Any particle fluid that enters the bounding box is removed.
    
== Reduce substepping ==

You can lock the __Sub Steps__ parameter to a specific number so that adaptive substepping does not occur. 

Adaptive substepping means Houdini retries the step if it has an error, so the simulation will be faster if you can set it to have the right value to begin with. However, without enough substepping you will get stray particles or particle explosions.

For example, if you have a complicated simulation that you know needs 10x substepping to be stable, you could set the __Sub Steps__ parameter in the [DOP Network|/nodes/obj/dopnet] node to 10, and reduce the __Max Substeps__ on the [Particle Fluid Solver|Node:DOP/particlefluidsolver] to something like 4.