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changes.mady.by.user Svetlin Nikolov

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idFireSmoke_Dynamics_TimeScale

Time Scale | timescale – Specifies a time multiplier that can be used for slow motion effects. In order to achieve the same simulation look when changing the time scale, the Steps per frame value must be changed accordingly. For example, when decreasing the Time Scale from 1.0 to 0.5, Steps per frame must be decreased from 4 to 2. And of course, all animated objects in the scene (moving objects and sources) must be adjusted as well. Time Scale different than 1 will affect the Buildup Time of Particle/Voxel Tuners and the Phoenix Mapper. In order to get predictable results you will have to adjust the buildup time using this formula:
Time Scale * Time in frames / Frames per second

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idFireSmoke_Dynamics_Cooling

Cooling | cooling – This parameter controls the cooling of the fluid due to radiation. It gradually decreases the temperature until it reaches 300.

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Phoenix FD temperatures are in Kelvin, so 300 is room temperature - the temperature where the smoke neither ascends nor descends. A Cooling value of 1.0 corresponds approximately to the speed real smoke with a half thickness of 4 meters cools down. The real cooling is a very complicated process similar to the Global Illumination rendering, so here a simplified formula is used. You can find out more about Phoenix Grid Channel Ranges here.

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SPFExample

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Example: Steps Per Frame (SPF)


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The first series in this example shows the differences in a Fire/Smoke simulation when the Steps Per Frame is set to 1, 2, and 8.

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SPF = 1

 

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SPF = 2

 

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SPF = 8

 

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Active Bodies

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Interaction between Active Bodies and the Phoenix FD Fire/Smoke Simulator is not supported yet.

 

 

Active Bodies | use_activeBodySolverNode – Enables the simulation of Active Bodies. 

Solver | activeBodySolverNode – Specifies the Active Bodies Body Solver node holding the objects to be affected by the Phoenix FD Simulation. 

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TextureUVW
TextureUVW

Texture UVW

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The main purpose of the Texture UVW feature is to provide dynamic UVW coordinates for texture mapping that follow the simulation. If such simulated texture coordinates are not present for mapping, textures assigned to your simulation will appear static, with the simulated content moving through the image. This undesired behavior is often referred to as 'texture swimming'.

UVW coordinates are generated by simulating an additional Texture UVW Grid Channel which has to be enabled under the Output roll-out for the settings below to have any effect.

The custom UVW texture coordinates can be used for advanced render-time effects, such as recoloring of mixing fluids, modifying the opacity or fire intensity with a naturally moving texture, or natural movement of displacement over fire/smoke and liquid surfaces. Some examples uses are:

  • Increasing the detail of Fire/Smoke simulations at render time by adding displacement which moves along with the fluid.
  • Increasing the detail of Fire/Smoke simulations at render time by modulating the opacity of the smoke, the smoke color, or the fire color and intensity with noise maps which move along with the fluid.
  • Re-coloring of Fire/Smoke or Liquid simulations at render time, after the simulation is complete.
  • Transporting images or texture color details with Fire/Smoke or Liquid simulations.

The Texture UVW channel values represent the UVW coordinates of each Cell in the Simulator, with a range of [ 0 - 1 ]. The channel is initialized when a simulation is started in one of two ways:

  1. By inheriting the UVs from the source geometry, when Inherit TexUVW from Geom is enabled on the Phoenix FD Source. The UVW channel will be based on the UVs of the emission geometry. This option is useful when simulating melting objects – textures assigned to the Volumetric Shader (for Fire/Smoke simulations) or the material (for Liquid simulations) will be carried by the simulation.
  2. When inheriting of UVs is disabled on the Source - depending on the position of the emitting object in the Simulator's bounding box. If Grid roll-out → Adaptive Grid is enabled, the Texture UVW coordinates in expanded voxels beyond the initial grid will be greater than one if the grid is expanding in a positive direction (+X, +Y, +Z), and less than zero otherwise. This means that textures assigned to simulations using the Adaptive Grid feature will be automatically tiled/repeated as many times as the final size of the Simulator is larger than its initial size.


 

Interpolation | texuvw_interpol_influence – Blends between the UVW coordinates of the liquid particle at time of birth and its UVW coordinates at the current position in the Simulator. When set to 0, no interpolation will be performed - as a consequence, textures assigned to the fluid mesh will be stretched as the simulation progresses. This is best used for simulations of melting objects. When set to 1, the UVW coordinates of the fluid mesh will be updated with a frequency based on the Interpol.Step parameter - this will essentially re-project the UVWs to avoid stretching but cause the textures assigned to the fluid to 'pop' as the re-projection is applied. If you intend to apply e.g. a displacement map to a flowing river, set this parameter to a value between 0.1 and 0.3 - this will suppress both the effects of stretching and popping. See the Interpolation example below.

Interpol. Step | texuvw_interpol_step – Specifies the update frequency for the UVW coordinates. When set to 1, the UVWs are updated on every frame, taking into account the Interpolation parameter. See the Interpolation Step example below.

Antitear | texuvw_antitear_influence – Use this option when the assigned texture appears twisted, torn apart or otherwise distorted. This may happen when the simulation is moving very fast, therefore increase both the Antitear and A-tear Iterations to let Phoenix FD attempt to resolve the distortion.

A-tear Iterations | texuvw_antitear_iterations – The number of Antitear iterations performed for every Step of the simulation. Increasing this parameter will help resolve UVW distortion issues by allowing Phoenix FD to run the Antitear operation multiple times. Note that this may slightly increase the time it takes for the simulation to complete.

 

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Example: Interpolation

 

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The following video provides examples to show the differences of Interpolation values of 0, 0.1, and 1, and an Interpolation Step of 1.

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Example: Interpolation Step

 

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The following video provides examples to show the differences of Interpolation Step values of 1, 3, and 6.

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