Water Body

• The article on Water Mesh关于 Water Mesh 的文章
• BodyWater classBodyWater 类
• Fragment of the video tutorial on physics demonstrating the use of the Water body for simulation of various types of liquids演示物理学的视频教程的片段使用 Water body 模拟各种类型的液体

Liquidity defines the viscosity of water (or any other liquid): it determines how readily it splashes and affects wave formation. It multiplies the speed with which water particles pass velocity vectors to the neighboring ones.流动性定义了水（或任何其他液体）的粘度：它决定了它飞溅和影响波浪形成的难易程度。它乘以水粒子将速度向量传递给相邻粒子的速度。

• The higher the value, the more viscous the water is and the smaller are the waves risen by the objects (e.g. syrup).值越高，水越粘稠，物体（例如糖浆）引起的波浪越小。

• Low values provide higher surface waves (e.g. tap water).低值提供更高的表面波（例如自来水）。

  注意

  Be careful not to set too high or too low values, because that may lead to unstable simulation and blowing up of the water. To regain stability, try to tweak Interaction.注意不要设置太高或太低的值，因为这可能会导致模拟不稳定和水爆炸。要恢复稳定性，请尝试调整 Interaction。

Density of water determines the buoyancy of objects according to Archimedes' principle. Based on the volume of the submerged part of the shape and its mass, buoyancy force is applied to its center of mass and pushes the object upwards, whereto the mean normal of the grid covered by submerged shape points.根据阿基米德原理，水的密度决定了物体的浮力。根据淹没部分的体积形状和它的质量，浮力被施加到它的质心并向上推动对象，其中被淹没的形状点覆盖的网格的平均法线。

• By the minimum value of 0, the objects will not float in the water, but rather fall through it without any resistance.通过 0 的最小值，物体不会漂浮在水中，而是在没有任何阻力的情况下通过它。
• Higher values increase the buoyant force. If set too high, the immersed objects start to be pushed out in the air.较高的值会增加浮力。如果设置得太高，浸入的物体开始被推出到空中。

A physical object submerged into the water (or any other liquid) has its own velocity vector. On the other hand, all the water particles that are covered by this physical body or surround it, have their own integrated velocity vector, which approximates the state of water. The Interaction value is a coefficient that determines how much the object's velocity influences the velocities of water particles and thus generate waves.浸入水（或任何其他液体）中的物理对象具有自己的速度矢量。另一方面，所有被这个物体覆盖或包围的水粒子，都有自己的积分速度矢量，近似于水的状态。 Interaction 值是一个系数，它确定对象的速度对水粒子速度的影响程度，从而产生波浪。

• By the minimum value of 0, an object produces no disturbances on the water surface.通过 0 的最小值，物体不会对水面产生干扰。

• Higher values make the disturbances of water surface more intense and the waves from moving objects become higher.值越大水面的扰动越强，在移动的物体浪变得更高。

  注意

  Too high values may blow the water up, as the law of conservation of energy does not constrain the system! Try decreasing damping values to regain stability.太高的值可能会把水吹起来，因为能量守恒定律不会约束系统！尝试减少减震值以恢复稳定。

Objects getting into the water are expected to slow down, as resistance of the water is higher than the drag in the air. Damping values work the other way around compared to the Interaction coefficient:进入水中的物体预计会减慢速度，因为水的阻力大于空气中的阻力。阻尼值与 Interaction 系数相反：

Linear Damping defines how much linear velocity of the submerged object is decreased over time when influenced by velocities of surrounding water particles. And similarly, Angular Damping defines the gradual decrease in the object's rotation. Both linear and angular damping forces are accumulated before being applied.Linear Damping 定义了在受周围水粒子速度影响时，水下物体的线速度随时间降低了多少。同样，Angular Damping 定义了对象旋转的逐渐减少。线性和角阻尼力在施加之前都会累积。

• By the minimum value of 0, objects movement is not hindered by the water. As a result, there are no waves in the water.通过 0 的最小值，物体的运动不受水的阻碍。结果，水中没有波浪。

• Higher values make the damping of linear or angular velocities more intense, and objects slow down faster as they get into the water. The waves from the objects in this case become more pronounced, as the energy of the system increases.较高的值会使线速度或角速度的阻尼更加强烈，并且物体在进入水中时会减慢速度。在这种情况下，随着系统能量的增加，来自物体的波变得更加明显。

  注意

  The water may blow up in case the values are be very high. Try decreasing the Interaction value to regain stability.如果值非常高，水可能会爆炸。尝试降低 Interaction 值以重新获得稳定性。

It is possible to create an additional visual effect of small droplets, splashes or bubbles on the water when objects fall into it. To enable this effect perform the following steps:当物体落入水中时，可以在水面上产生小水滴、飞溅或气泡的额外视觉效果。要启用此效果，请执行以下步骤：

1. Create a Particle system effect by clicking Create -> Effect -> Particle system in the main menu of UnigineEditor.通过单击主菜单中的 Create -> Effect -> Particle system 创建 Particle system 效果统一编辑器.
2. Go to the Parameters window.转到 Parameters 窗口。
3. In the Dynamic section, choose the Spark Emitter to spawn particles by selecting Emitter -> Spark.在 Dynamic 部分，选择火花发射器通过选择 Emitter -> Spark 来生成粒子。
4. Make Particle system a child of the Water Mesh object.使 Particle system 成为孩子Water Mesh 对象。

Particles will be generated only when the object first contacts the water surface, while already submerged bodies will float without generating them.只有当物体第一次接触水面时才会生成粒子，而已经淹没的物体将漂浮而不生成它们。

Effect of water splashes水溅效果

Depth determines the size of waves: high waves are formed in deep waters (e.g. a sea), while only a slight ripple is generated in shallow waters (e.g. a pool):Depth 决定了波浪的大小：在深水（如大海）中会形成大浪，而在浅水（如水池）中只会产生轻微的波纹：

• With the minimum value of 0, the objects raise no waves in the water.最小值为 0 时，对象不会在水中产生波浪。
• Higher values result in higher waves generated by moving objects.较高的值会导致移动对象产生较高的波。

Intersection of water with the underlying terrain can be necessary, for example, to estimate the actual depth of the water basin. To enable ground intersection perform the following steps:Intersection 的水与底层地形可能是必要的，例如，估计实际深度的水盆。 要启用地面交叉，请执行以下步骤：

1. Make Water Mesh or Dynamic Mesh object a child node of the Terrain or Static Mesh使 Water Mesh 或 Dynamic Mesh 对象成为 Terrain 或 Static Mesh 的子节点
2. Check the Intersection box in the Parameters window -> Physics tab -> Body section.选中 Parameters 窗口 → Physics 选项卡 → Body 部分中的 Intersection 框。

Intersection is implemented in the following way: the rays are traced downwards from the water mesh surface, as far as the Depth distance. If a ray intersects the parent node, the obtained depth is used in calculations; otherwise the preset depth value is used.相交以下列方式实现：光线从水网格表面向下追踪，直到 Depth 距离。如果一条射线与父节点相交，则将获得的深度用于计算；否则预设深度值用来。

Intersection is also traced upward to check if the water is under terrain and there is no need to render it.交叉点也向上追踪以检查水是否在地形下并且不需要渲染它。

Absorption is an option that creates either an effect of a limited basin or, on the contrary, of an open water surface that does not have marked boundaries.Absorption 是一个选项，可以创建有限盆地的效果，或者相反，创建没有明显边界的开放水面。

• If Absorption is enabled, the waves are dispersed along the mesh perimeter. In this case the water level at mesh edges will gradually fall down to zero level.如果启用Absorption ，则波浪沿网格周长分散。在这种情况下，网格边缘的水位将逐渐下降到零水位。
• If disabled, the backwash from the wall is simulated: the wave when reaching the brink of the water is reflected and returns in the reversed direction.如果禁用，则模拟来自墙壁的反冲：到达水边时的波浪被反射并以相反的方向返回。

Water body absorption: enabled(left) and disabled(right)Water body 吸收：启用（左）和禁用（右）