Fluid and Volumetric Rendering


X-Particles contains three fluid solvers: FLIP (Fluid Implicit Particle), Fluid FX and PBD (Position Based Dynamics) objects.

With the FLIP solver it is important to remember that unlike the PBD fluid object and FluidFX, FLIP only works within the space that it encloses (the domain). Particles or objects outside the domain are unaffected by it.


Using the FLIP domain for fluids is very simple. After creating an xpFluidFLIP object, add an emitter and ensure it is within the domain. You might also want to add something like a Gravity modifier to ensure the liquid flows downwards. Play the animation and you will see something like this:

You can see that the particles stay within the domain bounds by bouncing off the walls (this is because all the walls are in place - they will flow out if a wall is not present. See the xpFluidFLIP object for details.).

That's all there is to it. You can alter the other properties in the xpFluidFLIP, especially Vorticity and Viscosity, then render the particles either with an X-Particles Material or by using the OVDB Mesher to generate a mesh. You can use other modifiers to influence the flow: Wind, Turbulence and Drag all produce nice effects. You can add objects to the scene and use the Collider tag to create an 'obstacle' (FLIP systems don't have collider objects, they have obstacles the particles will flow round) or the Avoid modifier for slightly different results.

FLIP fluids are very fast and powerful, the main disadvantage being that they are confined to the boundaries of the domain. If this is an issue, use one of the other fluid solvers instead. But note that if you want the fluid to be contained within an object you will have to set that up yourself with the required objects and collider tags. For example, to reproduce the above example using FluidFX, you might create a cube primitive with a collider tag set to inside normals and place an emitter inside the cube.

Fire and Smoke

To generate these effects use ExplosiaFX. The FLIP domain no longer supports fire and smoke generation. You will need a source object for the fire/smoke. To try this, add an object such as a Sphere to the scene, ensuring it is within the bounds of the ExplosiaFX object, and attach an EFX Source Tag to the sphere. The source of the simulation is now the sphere, and you don't need an emitter.

The default settings in Explosia will produce a result like this:

Rendering the result

To render the smoke, fire etc., create an X-Particles Gaseous Material and apply it to the ExplosiaFX object. Rendering the above example would show this:

Of course, much better results can be obtained but this is to demonstrate how simple it is to set up and render fire and smoke using ExplosiaFX in X-Particles.

We recommend using Cycles 4D for rendering fire and smoke which gives faster and better results.

Further information

For more information about these systems please see the following pages:

Simple Volumetric Rendering

In addition to ExplosiaFX, the X-Particles Material can render particles volumetrically to give smoke-like effects without the overhead of Explosia.

To do this, apply the material to an emitter and in the material turn on 'Volumetric' in the volumetric tab. You can alter the colour, transparency, etc. in the usual way.