Lesson 1: Creating a Water style nParticle object

Lesson setup

To ensure the lesson works as described, do these steps before beginning:

Open the scene file named Liquid_Simulation_1.mb.
This file can be found in the GettingStarted directory that you set as your Maya project:
```
GettingStarted/nParticles/Liquid_Simulation_1.mb
```
This scene includes textured models that have been created for you. The desk, water pitcher, and water glass provided are all polygon meshes. The water pitcher mesh is animated so that it lifts off the desk, tips as to pour into the glass, and then sets back down to the desktop.

Create a Water style nParticle

Using a Water style nParticle will presets some nParticleShape attributes, including Liquid Simulation attributes, as well as set the Particle Render Type to Blobby Surface.

To create a Water style nParticle object

Select nParticles > Create nParticles, and select Water.
Selecting Water presets some nParticleShape attributes for liquid simulations.
Select the geometry that you want to fill with the Water style nParticle. In this case, select the water pitcher mesh. To do this, in the Outliner, select geo_pitcher, contained in the grp_Pitcher object.
Select nParticles > Create nParticles > Fill Object > .
The Particle Fill Options window appears.
In the Particle Fill Options window, select Edit > Reset > settings.
From the Solver list, select Create New Solver.
Ensure that Resolution is set to 10.
Resolution specifies how many nParticles are evenly placed along the fill geometry’s longest axis.
Ensure that Close Packing is turned on.
Turn on Double Walled.
Turning on Double Walled ensures that the thickness of the pitcher's geometry is taken into account, meaning that the particles only fill the pitcher's empty volume, rather than between the polygon walls.
Click Particle Fill.
In the Outliner, double-click nParticle1 and type nParticle_Water.
Renaming your nParticle object makes it easier to identify it when you have more than one in your scene.
Play back the simulation.

The nParticles fall through the bottom of the mesh water pitcher and disappear from the scene. This is because the nParticles do not recognize the object they are contained in.

In this tutorial, as you simulate the pitcher pouring water into the glass, both the pitcher and glass meshes must be converted to passive collision objects.

Creating passive collision objects

For the nParticles to interact with the water pitcher mesh, it must be converted to a passive collision object and assigned to the same Nucleus system.

To convert the pitcher and glass meshes to passive collision objects

Rewind the simulation to the start frame.
In the scene view, -select the pitcher and glass meshes.
Select nMesh > Create Passive Collider > .
The Make Collide window appears.
From the Solver list, select nucleus1.
Click Make Collide.
To rename the pitcher and glass nRigid objects, in the Outliner, double-click nRigid1 and nRigid2, and type nRigid_Pitcher and nRigid_Glass respectively.
Play back the simulation.
When you play back the simulation, you notice that the nParticles are not behaving as you might expect. Rather than immediately falling to the bottom of the pitcher like water, they fall slowly, as if the simulation was playing back in slow motion.

Before you begin simulating your liquid nParticles, it is important to adjust the Nucleus solver properties to suit your simulation. The Maya Nucleus solver properties control internal forces that affect all of the nodes that are members of a particular solver system. One of the most important Nucleus solver attributes to be aware of is Space Scale. When Space Scale is set to its default value of 1, the Nucleus solver applies Gravity and Wind to objects as if the objects were scaled in meters.

To edit Space Scale

In the Attribute Editor, click the nucleus1 tab.
In the Scale Attributes section, set the Space Scale to 0.01.

By reducing the Space Scale value, Maya evaluates the nParticle system as if they were much smaller in size. This will result in a visibly increased gravitational affect on the nParticles.
Rewind the simulation to the start frame, and then play it back.

When you play back the simulation, you notice that the nParticles are now contained in the pitcher, but they occupy a small amount of the pitcher’s volume. Also, the nParticles appear to be pushing down as if they are under a force of pressure or compression. In the next section, you begin adjusting the Liquid Simulation attributes that make the nParticles look and behave like a liquid.

Beyond the lesson

In this lesson you learned how to:

Use Fill Object to create an nParticle system.
Create passive collision objects to contain your nParticles.
Adjust the Nucleus slover’s Space Scale attribute to suit the scale of your simulation.