PhoenixFD插件流体模拟——UI布局【Splash | Mist】详解

液体飞溅 | 水雾

本文主要讲解Splash | Mist折叠栏中的内容。原文地址：https://docs.chaosgroup.com/display/PHX3MAX/Liquid+Splash+%7C+Mist

主要内容

• Overview 综述
• Parameters 参数
  • Splash Birth 飞溅产生
  • Mist Birth 水雾产生
  • Foam On Hit 击打产生泡沫
  • Properties 属性
    • Example: Splash Amount
    • Example: Liquid-Like

Overview

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This rollout affects the splash and mist simulation.这个折叠栏影响飞溅和雾模拟。

Because these systems are closely related and share many properties, they are controlled by a common user interface.由于这些系统紧密相关并共享许多属性，所以它们由一个公共用户界面控制。

A splash/mist rollout, separate from the liquid simulation, is provided in order to optimize memory and CPU usage.该折叠栏与流体仿真分离，是为了优化内存和CPU使用而提供的。

While normal liquid simulation can produce splash, and if you increase the resolution to incredible values it will produce mist as well, such a simulation would run slowly and consume an incredible amount of resources.正常的液体模拟会产生飞溅，如果你把分辨率提高到难以置信的数值，它也会产生雾，这样的模拟会运行得很慢，消耗大量的资源。

Besides saving on resources and rendering time, there is another strong advantage to controlling splash and mist separately from the liquid itself: different shaders can be used for splash/mist and the liquid.除了节省资源和渲染时间外，将splash和mist与液体本身分开控制还有一个强大的优势:可以使用不同的着色器对splash/mist和液体进行着色。

Splash and mist can be simulated in two different ways: as fully separated systems (non-physical mode), or as part of the liquid simulation (physical mode, the default).

飞溅和薄雾可以用两种不同的方式进行模拟:作为完全分离的系统(非物理模式)，或者作为液体模拟的一部分(物理模式，默认)。

In physical mode, the liquid, splash and mist systems can be seen as a single system with adaptive levels of detail.在物理模式下，液体、飞溅和薄雾系统可以看作是一个具有自适应细节级别的单一系统。

Following certain rules, the liquid can be converted into splash, the splash can be converted into mist or back into liquid, and the mist can be converted into liquid.

根据一定的规律，液体可以转化为飞溅，飞溅可以转化为水雾，也可以转化为液体，水雾也可以转化为液体。

！ Users of previous versions should note an important difference about splash regarding particle size.以前版本的用户应该注意到splash在粒度方面的一个重要区别。

In version 2.2 the splash size was controlled directly, like the foam.在版本2.2中，飞溅大小是直接控制的，就像泡沫一样。

While foam really needs direct size control, especially for the most popular usage of pouring a glass of beer or soda, the size and volume of a splash should be directly related to the amount of liquid being displaced rather than a user-specified value.虽然泡沫确实需要直接控制大小，特别是对于最流行的倒一杯啤酒或苏打水的方法，但飞溅的大小和体积应该与被取代的液体量直接相关，而不是用户指定的值。

In other words, in order to have a seamless transition between the splash and the liquid, the volume of the splash droplets must be equal to the volume of the liquid converted into splash.换句话说，为了在飞溅和液体之间实现无缝过渡，飞溅液滴的体积必须等于转化为飞溅的液体的体积。

Phoenix 3.0 and newer simulates splashes according to this rule. Here is an image that may help visualize this process - FLIP Particles Life Cycle.

UI Path: ||Select Liquid Simulator | LiquidSim object|| > Modify panel > Splash/Mist rollout

参数

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Enable | splashes – Enables splashes in the simulation. 在仿真中启用泼溅

产生泼溅

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Splash Amount | spbirth – Controls the amount of splash relative to the liquid.控制相对于液体的飞溅量。

This value determines how many splash particles are equal to a single liquid particle in volume.这个值决定了多少飞溅粒子等于一个液体粒子的体积。

This value also affects the particle size, where larger values decrease the size of splash particles.这个值也会影响颗粒大小，较大的值会减小飞溅颗粒的大小。

Note: This parameter is the nearest in functionality to the "birth rate" parameter in previous versions. 注意:这个参数在功能上与以前版本中的“出生率”参数最接近。

For more information, see the Splash Amount example below. 

Threshold | spbthres – Controls the condition for splash birth.控制飞溅产生的条件。

The lower this value is, the more places on the liquid surface will produce splash.值越小，越容易产生飞溅。

By Free Fly | spfreefall – The probability of a free falling/flying liquid particle converting into splash.自由下落/飞行的液体粒子转变为飞溅的可能性。

At 0.0, no free falling/flying liquid is converted into splashes.0表示没有流体可以转化为飞溅。

The main usage of values above 0.0 is in waterfall simulations.0.0以上值的主要用途是在瀑布模拟中。

It is not recommended that this parameter be changed to a value other than 0.0 for ocean simulations because the main body of liquid might sometimes be in a temporary state of free fall.

对于海洋模拟，不建议将此参数更改为0.0之外的值，因为液体主体有时可能处于自由落体的临时状态。

Birth Volume | usespbconfgeom, spbconfgeom – When enabled, allows the splash to be born naturally by the simulation only inside a specified geometry object.当启用时，只允许在指定的几何对象内通过模拟自然生成飞溅。

The splash born inside the Birth Volume can travel outside the volume without a problem.在出生卷内产生的飞溅可以毫无问题地传播到卷外。

The difference between this approach and spawning splash inside a volume manually from a Source object is that using a Birth Volume, the splash birth will follow the simulation criteria of the simulation and will look and behave more naturally.这种方法与从源对象手动在卷中生成splash的区别在于，使用Birth Volume时，splash生成将遵循模拟的模拟标准，并且外观和行为将更加自然。

！By default, the birth volume geometry is not automatically converted to a non-solid and it will behave as a rigid body in your simulation.默认情况下，出生体几何形状不会自动转换为非实体，在模拟中它将表现为刚体。

In this case, the Volume Fadeout can be used to expand an area around the object where Foam/Splash births are possible.在这种情况下，可以使用Volume Fadeout来扩展对象周围可能出现泡沫/飞溅的区域。

You can convert the geometry to a non-solid from its PhoenixFD properties.您可以将几何图形从PhoenixFD属性转换为非实体。

Volume Fade Dist | spbconfgeomfade – Controls how far the splash particles will spawn around the specified Birth Volume geometry object.控制飞溅粒子围绕指定的产生几何对象生成的距离。

产生薄雾

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Splash to Mist | spsplit – Controls how fast the splash particles are converted into mist. This value determines the portion of the splash volume that is turned into mist after traveling one meter (3.3 feet). During its motion, a splash particle constantly produces mist particles, decreasing the volume of the splash. When the entire volume is exhausted, the splash particle disappears. This parameter controls how fast this happens. If the value is 0.0 the mist is not simulated at all, and if you restore a simulation containing mist, the mist will be deleted.

Mist Amount | spmistmult – Controls the amount of mist. This value determines how many mist particles are spawned by a single splash particle.

Birth Volume | usemistbconfgeom, mistbconfgeom  – When enabled, allows the mist to be born naturally by the simulation only inside a specified geometry object. The mist born inside the Birth Volume can travel outside the volume without a problem. The difference between this approach and spawning mist inside a volume manually from a Source object is that using a Birth Volume, the mist birth will follow the simulation criteria of the simulation and will look and behave more naturally.

By default, the birth volume geometry is not automatically converted to a non-solid and it will behave as a rigid body in your simulation. In this case, the Volume Fadeout can be used to expand an area around the object where Foam/Splash births are possible. You can convert the geometry to a non-solid from its PhoenixFD properties.

Volume Fade Dist | mistbconfgeomfade – Controls how far the mist particles will spawn around the specified Birth Volume geometry object.

击打产生泡沫

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Foam Amount | sp2foam – Controls how many foam bubbles are created when a single splash particle hits the surface.控制当单个飞溅粒子撞击表面时产生多少泡沫。

This parameter works in terms of probability.这个参数以概率的形式工作。 Non-integer values can be used. 可以使用非整数值。

Min. Age | spfohminage – Minimum age for foam production.生产泡沫塑料的最低年龄。

Only splash particles with a particle age above this limit will produce foam when they hit the liquid surface.只有颗粒年龄超过这一极限的飞溅粒子在撞击液体表面时才会产生泡沫。

！For the Min. Age parameter to work, you need to Enable the export of the Age channel for your Splash particles from the Output menu of the Phoenix FD Simulator.此参数需要在输出折叠栏中打开Age参数。

Depth | fohdepth – When a splash particle hits the liquid surface and produces foam, this parameter specifies how far in front of the splash particle the new foam particles will be born.

当飞溅颗粒撞击液体表面并产生泡沫时，此参数指定新泡沫颗粒将在飞溅颗粒前面多远的地方产生。

This parameter is used mostly to create underwater foam that will be colored by the fog color of the liquid.这个参数主要用于创建水下泡沫，它将由液体的雾色着色。

属性

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Splash Air Drag | airfr – The air friction of the splash droplet.飞溅液滴的空气摩擦。

A value of 1 represents the air friction of an average rain droplet.值1表示平均雨滴的空气摩擦力。

Mist Air Drag | mistdrag – The air friction of the mist.水雾的空气摩擦。

This value determines not only how fast the speed decreases, but also the influence of the wind.这个值不仅决定了风速下降的快慢，还决定了风速的影响。

The larger this value, the larger the wind's influence.

Max Outside Age | timeout – If a particle exits the grid and its age exceeds this parameter, it will be killed instantly.如果一个粒子离开网格并且它的年龄超过这个参数，它将立即被杀死。

This parameter affects both splash and mist.同时影响飞溅与水雾。

！For the Max Outside Age parameter to work, you need to Enable the export of the Age channel for your Splash particles from the Output menu of the Phoenix FD Simulator.

要使最大外部年龄参数工作，您需要从Phoenix FD模拟器的输出菜单中为您的飞溅颗粒启用年龄通道的导出。

Initial Vel. Mult. | spvmult – When the splash particles are born, they are initialized with the velocity of the nearest liquid multiplied by this value.当飞溅粒子产生时，它们的初始化速度是最近的液体的速度乘以这个值。

This parameter greatly affects the general appearance of the splash.这个参数对飞溅的总体外观有很大的影响。

When it is below 1, the droplets fly in front of the splash and produce a clearly visible track of droplets.当值低于1时，水滴就会飞到飞溅点的前面，并产生清晰可见的水滴轨迹。

Initial Vel. Rand. | spvrand – Controls the randomness of the velocity direction when splash particles are born.控制飞溅粒子产生时速度方向的随机性。

Liquid-Like | spstick – Controls the ability of the splash particles to stick to each other, forming different strings and tentacles.控制飞溅粒子相互粘附的能力，形成不同的弦和触须。

The higher this value, the larger the acceleration needed to break the connection.这个值越高，断开连接所需的加速度越大。

As this parameter controls the bubble-to-bubble interaction of the foam and its viscosity, larger values increase calculation time. 由于该参数控制了泡沫与泡沫之间的相互作用及其粘度，数值越大，计算时间越长。

For more information, see the Liquid-Like examplebelow. 

Affect Liquid | affectlq – Controls the conversion of liquid to splash, and splash back into liquid.控制液体飞溅和飞溅回液体的转换。

When this value is not zero, the splash birth causes some of the liquid to disappear, and then when the splash enters the liquid the splash particles are replaced by liquid.

当这个值不为零时，飞溅的产生导致一些液体消失，然后当飞溅进入液体时，飞溅颗粒被液体替代。

A value of 1 with splashes and mist enabled produces a physically accurate simulation where liquid, splash and mist are constantly converted into one another, and the sum of all three at any point during the simulation is the same as the original liquid.启用飞溅和雾的值1可以生成物理上精确的模拟，其中液体、飞溅和雾不断地相互转换，并且在模拟过程中任意时刻三者之和与原始液体相同。