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This page provides a step-by-step guide for understanding solid and non-solid bodies in Chaos Phoenix FD for Maya.

Overview

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This is an Entry Level tutorial which requires no previous knowledge of Phoenix FD. A basic understanding of Maya would be helpful but is not a prerequisite for being able to follow along.

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The instructions on this page covers the basic workflows for using Solid and Non-Solid bodies in Phoenix FD for Maya. By the end of this tutorial, you will be able to use Solid and Non-Solid bodies to control interactions and customize simulations.

To follow the described steps, you will need the Phoenix FDPhoenix for Maya plugin installed. If you notice a major difference between the results shown here and the behavior of your setup, please send an email to support@chaosgroup.com.

This tutorial is a companion to go along with the QuickStart video posted on our YouTube channel.

 

The Download button below provides you with an archive containing the start and end scenes.

 

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urlhttps://drive.google.com/uc?export=download&id=1-Ng8iQ5ods3OjSGiqJ7a_cI-d60t16ql
 

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The video is created using Phoenix FD 3.0, but the text version of the tutorial is updated and uses Phoenix FD 4.30 Official. In any case of doubt you may refer to the text.

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Scale is crucial for the behavior of any simulation. The real-world size of the Simulator in units is important for the simulation dynamics. Large-scale simulations appear to move more slowly, while mid-to-small scale simulations have lots of vigorous movement. When you create your Simulator, you must check the Grid rollout where the real-world extents of the Simulator are shown. If the size of the Simulator in the scene cannot be changed, you can cheat the solver into working as if the scale is larger or smaller by changing the Scene Scale option in the Grid rollout.

The Phoenix FD solver is not affected by how you choose to view the Display Unit Scale - it is just a matter of convenience.

 

Go to Windows → Settings and Preferences → Preferences → Settings and set the Working Units to Centimeters.

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With the sphere still selected, click on the Large-scale Smoke sim Preset button from the Phoenix FD Shelf.

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Select the Simulator. In the Attribute Editor under the Grid rollout are located the parameters to control the resolution of the volume grid, which greatly affects the look and performance of the simulation.

Currently, there are about 300,000 Total Cells. To save on simulation time during the iteration process, click Decrease Resolution six times until the Total Cells are around 5,000.

 

For more information regarding simulation resolution, please refer to the Basic Liquids QuickStart page.

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We can clearly see that the Smoke collides with the box, and goes around it. And we didn’t need to do anything to make that happen. That’s because, by default, meshes are treated by Phoenix FD as Solid Objects, which means the object becomes an obstacle to the fluid's motion.

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Make sure that any mesh you want to use in this manner is closed. Don’t use planes or flat sheets of geometry. If you need to use geometry that appears flat, you will need to add a small amount of thickness to it so it calculates properly within the simulation.


Press 4 or use the Wireframe icon located in the upper viewport menu to switch to Wireframe mode for better visibility.

Notice that the inside of the object is empty, and the Smoke goes around the volume, as shown in the picture.

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There is a difference between having a Non-Solid Object, like we have right now, and excluding an object from the interaction.

A Non-Solid Object, such as the one in the scene, can still be used with Forces (e.g. as an attractor for the Body Force) and also as an Emitter by Source objects. It can also be used as a Render Cutter, or a Birth (or ignition) Volume, and so on.

On the other hand, objects excluded through the Scene Interaction rollout will not interact at all with the simulation.

Now we’ll make the Smoke inside the Non-Solid box disappear.

Select the box and access the Extra Phoenix FD Attributes. Enable the Clear Inside option, which lists the different channels of the simulation that are affected. You can edit this list to control what kind of particle channels are cleared inside the Non-Solid.

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The difference between the Solid Object that we had before, and this Non-Solid with Clear Inside, is that the fluid moves around Solids but passes right through the Non-Solids. This way you can use Non-Solids with Clear Inside to erase Smoke, Temperature, Liquid, or different particles from certain areas of the Simulator without effecting the fluid's behavior.

While the simulation continues, create another Box in the scene that is a similar size to the first one. Move it up, inside the container in the path of the Smoke, and it traps some of the Smoke inside it, as in the image.

When creating or moving a Solid Object inside a Fire/Smoke simulation container, it can trap fluid channels inside itself. Note that this behavior does not apply to a Liquid Simulator.

Move this box around some more and you can see that some of the Smoke trapped inside the volume earlier is still stuck inside, and it may capture more.

Again, that’s because by default, all objects are treated as Solid Objects, so the Smoke can’t escape once inside.

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Select that second box and open its Extra Phoenix FD Properties. Turn on Clear Inside.

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The Smoke is gone from inside that box.

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Finally, select the first box and disable the Clear Inside, so the Smoke goes right through it.

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The box on the left is a Solid Object and the box on the right is a Non-Solid Object. Moving the Non-Solid box inside the Simulator changes nothing - it does not change the behavior of the simulation.

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But if you move the Solid Object box, it effects the Smoke simulation. If you move it around, the Smoke gets pushed to the side.

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You can control how strongly a moving Solid Object effects the simulation from its Phoenix FD Attributes using the Motion Velocity Effect parameter.

We will take a look at this in our next example.

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Example Scene

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Let’s apply these same concepts as we crash a spaceship into a body of water. We will use Solids, see how the Motion Velocity Effect works, and add Foam and Splashes in our simulation.

Open the provided scene file PhoenixFD_QS03A_SolidsNonSolids_start.ma.

The scene contains a spaceship crashing into the ocean.

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Next, create a Phoenix FD Ocean.

Select the spaceship and choose the Setup an Ocean preset from the Phoenix FD Shelf.

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Select the Simulator and navigate to the Grid rollout.

Make the simulation grid a bit smaller with an X/Y/Z Size of 150, 93, 150.

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