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This page introduces the Fire Smoke Simulator object (PhoenixFDSimulator) and its rollouts.

Overview

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A The Fire/Smoke simulator is a Phoenix object that controls the simulation, and enables you to create fluids like liquids and gasses that interact with the surrounding environmentintended to produce gaseous effects like fire, smoke and explosions, as well as sparks or embers.

You can think of a Phoenix Simulator as a 3D box, inside which simulations of fluids and Rigid Body Dynamics are performed. The box is divided into small cells, called voxels, which is why the box is referred to as a Simulation Grid. The voxels inside the grid can be filled with just about any type of gas or liquid, and contain the fluid's properties at a position and given time.For each frame in your simulation, Phoenix looks at each voxel and calculates whether there is any fluid there, based on the settings you give the Phoenix sim. The simulator will also account for obstacles, such as geometry, as well as participating forces in the scene, and so forth.

Although Chaos Phoenix for Maya uses a single Simulator node for both, Phoenix simulations can generally be divided into two types:

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  • Fire/Smoke simulations, which include gaseous effects like fire, smoke and explosions, as well as sparks or embers and so forth.
  • Liquid simulations, which can create pouring or flowing liquids, or any simulation that needs foam or mist, such as coffee or waterfalls.

Since Liquid simulations have peculiar properties that differ from those of Fire and Smoke simulations, the simulator contains a separate Liquid rollout. There are also separate rollouts for controlling when Foam, Splash and Mist Particles should be born, and how they should behave.

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To actually create a simulation, three different components must be combined:

  1. A Simulator node

  2. A Source node

  3. An Emitter

This is the minimum requirement for just about any simulation setup.

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The only exceptions are that you can also simply fill the simulator with liquid using the Initial Fill Up parameter in the Liquid rollout. Likewise, a specified geometry can also be filled with liquid, without any need for a Source or Emitter, using the Initial Liquid Fill parameter in the object's Phoenix Node Properties.
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Note that in addition to the manual creation of a simulator using the UI paths shown below, a simulator is automatically created when any of the Quick Simulation Setup buttons are used.

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UI Paths: ||Phoenix FD menu|| > Create > 3D or 2D Simulator

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||Phoenix FD Shelf|| > Create Phoenix FD Fluid Simulator button

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The workflow for Phoenix fluids and Active Bodies is split into two main parts – simulating and rendering.

Simulating Fire and Smoke

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These fluid properties are written inside what are called Grid Channels.

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Each channel stores a type of value, such as Temperature or

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Velocity, with its own Grid Channel Range, which is the range of possible values that is most efficient for that specific channel type

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. Phoenix determines the fluid’s behavior at a given time, based on the content of these

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Simulating Liquids

Liquid simulations also generate particles for liquids that drive the simulation, by writing simulation data inside each voxel’s Grid Channels, so that the Grid Data is built from those particles. 

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Grid

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Phoenix generates particles for liquids because they are useful for representing the characteristics and behavior of a fluid, and as a result look more natural when rendering liquids, especially when generated in very large amounts. The particles emulate real-world fluids by moving through 3D space within the simulation grid, and unlike voxels, each particle carries its own fluid properties with it, such as Position, Age, Velocity and so forth. These properties contained in each of the particles are called Particle

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, and their values can change every frame, based on each channel's Particle Channel Range

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Besides liquid, the simulator provides built-in helper simulators for Foam, Wetmap, Splash, and Mist Particles. In certain cases, the splash and mist can be considered as part of the liquid simulation, because liquid, splash and mist can be converted to each other during the simulation process. You can go through the FLIP Particles Life Cycle page for an in-depth explanation of this process.

Cache Files

When running a simulation, the

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Fire/Smoke sim will typically output an entire animation sequence. That sequence is saved as individual files, called caches, which contain raw simulation data for each timeline frame. In essence, the cache data contains grids and particles, which describe the fluid’s behavior.

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Fire/Smoke

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sim cache files can then be previewed in the viewport

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, as well as rendered, in order to create captivating and realistic images.

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The simulator offers multiple render modes

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, where the volumetric render modes are typically used for rendering Fire/Smoke

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sims, and the mesh render mode is typically used for Liquid sims. Phoenix offers a lot of flexibility though, so there is the option to render Fire/Smoke sims as meshes and Liquids as volumes, in order to achieve even more diverse effects.

When rendering other particle types besides Phoenix Liquid Particles, Phoenix has a separate Particle Shader geometry type, which is used to shade particles.

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The Particle Shader component is most often used in conjunction with Liquid simulations to shade particles such as Splash, Mist and Foam. However, it can also shade Drag particles created using the Fire Source, as well as standard particle systems such as nParticles in Maya.
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Note that the simulator is represented as a single object for convenience. Internally, it contains two completely separate parts: a simulator component , and a rendering component. Parameters that control the simulation are separated from those associated with the shading , meshing and rendering processes. As a result, no rollout roll-out will contain mixed parameters, and no parameter will affect both the simulation and rendering.
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UI Paths: ||Phoenix FD menu|| > Create > Fire/Smoke Simulator

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||Phoenix FD Shelf|| > Create Phoenix Fire/Smoke Simulator button

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Rollouts

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After creating a Phoenix Simulator object, the following rollouts can be accessed in the Attribute Editor:

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  • Simulation - Controls the simulation and displays statistics such as simulation times, as well as information about the data contained in the sim for the current frame.

  • Simulation Speed - Helps identifying the heaviest computation phases of the simulation and provides tips on how to get results faster and more efficiently.

  • Resimulation - Uses a base simulated cache sequence with exported velocity to drive a new simulation, in order to enhance details, increase its resolution, or slow down or speed up the simulation. For liquid simulations, it modifies an existing cache sequence to improve features or change specified particle systems.
  • Grid - Controls the boundaries, size and resolution of the simulation grid.
  • Dynamics - Offers parameters to affect fire/smoke dynamics when simulating, such as cooling, smoke dissipation, vorticity, advection, etc.
  • Fuel - Controls the simulation of burning when Fuel is present in the simulation, which is useful for creating gasoline explosions or propagating fire effects.Liquid - Controls liquid dynamics such as viscosity, surface tension, drying time, etc.
  • Foam - Controls the simulation of bubbles and foam.
  • Splash and Mist - Controls the simulation of splash and mist.
  • Scene Interaction - Specifies how the simulator interacts with other objects in the scene.
  • Output - Specifies how and where the simulation cache files are saved.
  • Input - Determines the path of the input files for rendering and previewing, and offers settings and controls for playback.
  • Preview - Controls how the simulation is displayed in the viewport.
  • Rendering - Controls how the simulation is rendered, and includes additional volumetric options for shading Fire/Smoke simulations.

Simulation in 2D

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  • Presets – Allows the parameters of the simulator to be saved to your storage, and then loaded back as a preset.


Upgrading from Previous Versions of Phoenix

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Due to many improvements to the Phoenix solver, recreating simulations the same way you did in older versions of Phoenix may not be possible because of changes to the solvers and the UI. Here are some things to be aware of when upgrading from older versions of Phoenix. 


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  • If you have a scene created with Phoenix version 3 and you open it with version 4, it will keep all the old settings for you, including some which are not visible to newer versions, in order for the results to be roughly the same.

  • If you try to manually replicate an older simulation setup with a new Phoenix simulator using Phoenix version 4, and set all the parameters with the same values as the older version, you may not obtain the same result as in Phoenix version 3 or older.

  • Since the release of Phoenix version 3, Phoenix started using a new solver for liquids and fire/smoke simulations, so simulation results will be different between Phoenix version 3 and version 2.