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Overview

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The rendering process in Chaos Phoenix is separated from the simulation , but process, because simulated caches contain only simulation data, and no render settings.

However, for ease of operation is performed by the same object that performs the simulation. However, this is only true for the grid's content, not for the particles contained in the cache file. If you want to render the secondary effect particles (foam, splashes, or drag particles), create a Particle Shader object and add the Simulator to it, so the Particle Shader can use the cache data loaded by the Simulatoruse, the Liquid Simulator object also contains a Rendering rollout. This rollout offers modes and options for rendering the simulator grid’s content.

Phoenix provides a ton of flexibility for rendering your caches, and offers multiple render modes that can be divided into two types: surfaces and volumetric.

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If you want to render the particle content of the Simulator (e.g. foam, splashes, or drag particles), create a Particle Shader object and add the simulator to it.

You may also check the Volumetric Rendering In-Depth guide for tips on speeding up the rendering of volumetric effects with V-Ray.

The surface rendering modes of the Phoenix Simulator make it behave just like any regular geometry - 3ds Max materials can be applied to the Simulator.

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Liquid simulations are typically rendered using one of the surface render modes. Meanwhile, volumetric modes are typically used for rendering fire and smoke.

By default, the Grid Liquid Channel is exported to the cache files during simulation, meaning that the simulator voxelizes the Liquid Particles into a Grid Channel. As a result, liquid simulations can indirectly generate a liquid surface from Liquid Particles.

This makes it possible to render the liquid as a mesh, using one of the surface render modes, such as Mesh, Isosurface, Cap Mesh and Ocean Mesh. The meshed liquid then behaves just like any regular geometry, meaning you can assign 3ds Max or V-Ray materials to the Simulator, and there is no need for a dedicated shader.

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The Rendering Rollout also contains additional controls for this meshing process, to customize the appearance of the surface.

Note that since Phoenix is very flexible, it also enables you to render liquid simulations using a volumetric render mode, to create more advanced types of effects.

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When rendering as a mesh, Liquid Particles are shaded by a material assigned to the Liquid Simulator object.

However, secondary effect particles such as Foam, Splash, Mist and Wetmap particles must be shaded using the Phoenix Particle Shader.

Simply create a Particle Shader object, and add the Liquid Simulator to it. The Particle Shader can then read the cache data loaded by the Simulator, and shade the particles as either Points, Bubbles, Cellular, Splashes, or Fog, depending on the mode you select.

Advanced control over the shading of Liquid Particles is provided with the Phoenix Grid Texture which . It can be used to drive the properties of a material applied to a liquid surfacea liquid surface, for example, to mix colored liquids together, or function as a mask for blending wet and dry materials when using Wetmap particles.

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UI Path: ||Select Select Liquid Simulator | LiquidSim object object||   > Modify panel > Rendering rollout


Actions

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Render settings are not stored within the caches themselves, so if you want to use the same render settings for another simulator or project, there is the option to save and load them as Phoenix Render Presets in the “.tpr” file format.

Render Presets... – Opens a menu for loading and saving different presets. The following options are available:

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  • Load from File...
  • Save to File...
  • Default .aur Render Settings
  • Fire/Smoke .aur Fast Render
  • Fire/Smoke from FumeFX
  • Fire/Smoke .vdb from Houdini
  • Liquid .vdb from Houdini
  • Fire/Smoke .vdb from Maya Fluids
  • Fire
  • Fuel Fire
  • Gasoline Explosion
  • Explosion
  • Large Smoke
  • Candle
  • Clouds
  • Cold Smoke

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Parameters

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Mode | rendMode – Specifies the method for visualizing the grid content.

Volumetric – Visualizes the content as a standard 3ds Max atmospheric. This method is used mostly for fire and smoke.
Volumetric Geometry – This method requires V-Ray. It produces the same result as the Volumetric option by using procedural geometry made up from multiple transparent layers. Used when rendering fire/smoke for exporting deep images and render elements such as normals, velocity, multi matte, etc. which would not be available in Volumetric mode. For more information on which render elements are supported in Volumetric and Volumetric Geometry mode, see V-Ray Render Elements Support.

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Approximate and Approximate+Shadows options for the Scattering parameter in the Smoke color window are not supported in Volumetric Geometry mode.

For a complete list of the supported Render Elements in both Volumetric and Volumetric Geometry mode, please check the V-Ray Render Elements Support page.

Volumetric Heat Haze – This method requires V-Ray. It produces the same result as the Volumetric Geometry option, and also adds a heat haze effect when used with the Heat Haze parameter. Note that you might need to increase the Max depth of a VRayMtl with refraction in case it intersects with the Heat Haze shader.

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ImplicitSurface
 Isosurface – This method requires V-Ray. It produces a procedural isosurface without polygons at render time using the Isosurface Level option. Compared to the Mesh mode, the result is always smooth but will take longer to render. In case in Mesh mode your mesh is too jagged and edgy, and smoothing it out is too slow or impossible, this means you should switch to Isosurface mode instead. 
Mesh – The content is converted into a standard 3ds Max mesh using the options in the Mesh Smoothing section. This mode is mostly used for liquids but can also be applied to thick smoke using a scatter material or to plumes of smoke to create effects such as large underwater bubbles.
Ocean Mesh – The grid content is extended to a flat area, fitting the camera's view.  In most cases, this mode is used with a displacement texture such as the Phoenix FD Ocean Texture.
Cap Mesh – Only the upper liquid surface is rendered. This mode can be used for swimming pools and other placid liquid surfaces.
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The ocean surface can be generated only when the liquid touches the sides and the bottom of the grid, which act as a container for the liquid. The detail of the mesh extension around the simulator depends on the camera resolution - for each pixel of the viewport or the rendered image, one or several polygons are generated, depending on the Ocean Subdivisions option.

Also note that if you use a material with fog color for the ocean mesh, and you have particles submerged below the ocean surface which you render using a Particle Shader, you need to also place a geometry that would serve as a bottom, or you could get flickering and darker rendering of the particles. For more info, see the Render as Geometry option of the Particle Shader.

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 Cutter Geom | usegizmo, gizmo – When enabled, rendering will occur only inside the selected geometric object's volume. Note that the Cutter Geom will not work when the render Mode is set to Volumetric Geometry.

Invert Cutter | invgizmo – When enabled, rendering will occur only outside of the render cutter. This is not the same as a cutter with inverted geometry because any rays that do not intersect the cutter will be shaded as well. 

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If using a Render Cutter for a liquid pouring into a glass or otherwise contained into another refractive object, you may need to set the Mode to Isosurface. By default, the mode is set to Mesh which may produce artifacts in the rendered image.

Surface Channel | sarg –  Specifies the channel that will define the surface of the fluid. It is used for solid rendering and displacement.

Texture - the values of a custom texture will define the mesh surface. You can see how this works in this How-to video.
Liquid - the Liquid channel will define the liquid surface. Liquid is typically in the range 0-1 for Liquid simulations.
Smoke - the Smoke channel will define the liquid surface. Smoke is typically in the range of 0-1 for Fire / Smoke simulations.
Speed - the Speed channel will define the liquid surface. Speed channel output has to be enabled for this to work. Speed is calculated as the length of the velocity vector for each voxel.  
Fuel - the Fuel channel will define the liquid surface. Fuel channel output has to be enabled for this to work. 
Viscosity - the Viscosity channel will define the liquid surface. Viscosity channel output has to be enabled for this to work.

Texture | stex – If the Surface channel is set to Texture, this slot specifies the texture. In Mesh, Ocean Mesh, Cap Mesh and Isosurface render modes, the selected map will completely replace the cache files that have been loaded, if any. For more information on texture mapping in Phoenix, please check the Texture mapping, moving textures with fire/smoke/liquid, and TexUVW page.

Invert Liquid Volume | solidbelow – By default, grid values above 0.5 are assumed to be liquid, and values below 0.5 are assumed empty. When enabled, the convention switches to the opposite such that values above 0.5 are assumed empty, and values below 0.5 are assumed to be liquid.  

Isosurface Level | surflevel - Allows you to specify a threshold value for the generation of the liquid surface. Grid cells below this value will be ignored. By default, the Isosurface Level is set to 0.5 and should only be modified if there is flickering in the generated geometry. Isosurface Level is used only in Isosurface, Mesh, Ocean Mesh and Cap Mesh Modes.

Isosurf. Sampler | sampler – Determines the blending method between adjacent grid voxels. Used to balance between rendering speed and quality. This parameter is only used when Mode is set to Isosurface.

Box – Displays voxels as cubes. There is no blending between neighbor voxels. This is the fastest mode.
Linear – Linear blending occurs between neighbor voxels to smooth out the fluid's look. Sometimes this mode may unveil the grid-like structure of the fluid. Up to 20-30% faster than the Spherical option.
Spherical – Uses special weight-based sampling for the smoothest looking fluid. With increasing resolution, the visual advantage of this method over the Linear method becomes less noticeable.

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