Rope Body

Rope body enables physical simulation of ropes, cables, wires, etc. Ropes can be pinned to the following types of bodies:Rope body 可以对绳索、电缆、电线等进行物理模拟。绳索可以固定到以下类型的物体上：

• Rigid body
• RagDoll body
• Dummy body

To pin a rope to a body so it would hang freely, or tie several bodies, use a Particles joint. The Rope body can be torn as a Cloth body. Rope enhances the realism of simulated environment and saves the time of game artists as it replaces animation. However, simulation of this type of body is quite costly and it is strongly recommended to use distance optimization to avoid performance hits.要将绳索固定到物体上使其自由悬挂，或将多个物体绑在一起，请使用 Particles joint。 Rope body 可以撕成 Cloth body。绳索增强了模拟环境的真实感，并在替代动画时节省了游戏美术师的时间。但是，这种类型的身体的模拟成本相当高，强烈建议使用距离优化以避免性能下降。

注意

Rope body can be assigned only to Mesh Dynamic objects.Rope body 只能分配给 Mesh Dynamic 对象。

See also也可以看看#

The only acceptable mesh type for a Rope body is a cylinder. You can use a standard primitive cylinder to create a rope. The workflow in this case is as follows:Rope body 唯一可接受的网格类型是圆柱体。您可以使用标准的原始圆柱体来创建绳索。本案例的流程如下:

1. On the Menu bar, click Create -> Primitive -> Cylinder.在菜单栏中单击 Create -> Primitive -> Cylinder。

2. Specify desired rope parameters (length, radius) for a cylinder, e.g. the following:为圆柱体指定所需的绳索参数(长度，半径)，例如:

   

3. Click OK and place the cylinder somewhere in the world. It is created as a Static Mesh object. The object itself can be deleted, its mesh however is still available in the data/ folder.点击 OK 并将圆柱体放置在世界的某个地方。它被创建为一个 静态网格 对象。对象本身可以被删除，但是它的网格仍然在 data/ 件夹中可用。
4. Create a Dynamic Mesh object and use the cylinder mesh for it.创建一个动态网格 对象，并使用圆柱体网格。
5. Assign the rope body to the created dynamic mesh object.将绳子体分配 给创建的动态网格对象。

A Rope body is modeled as set of point masses (particles) located in the mesh vertices. Each particle is represented with a sphere shape and is linked together with other particles by inner spring joints that are located along the mesh edges. Inner joints allow to recreate mesh topology, on the one hand, and constrain stretching and folding, on the other.Rope body 被建模为位于网格顶点的一组点质量（粒子）。每个粒子都用球体形状表示，并通过位于网格边缘的内部弹簧接头与其他粒子连接在一起。一方面，内部关节允许重新创建网格拓扑，另一方面可以限制拉伸和折叠。

Each particle is characterized by a position, mass and velocity and has a constant spherical shape with a set radius. The total mass of the whole body is equally distributed among them. In accordance with Newton's second law particles can be acted upon by a force or an impulse applied by inner joints and external forces (collision, gravity, air resistance, wind, etc.).每个粒子都以位置、质量和速度为特征，并具有恒定的球形，并具有一组半径.总数大量的全身的能量在他们中间平均分布。根据牛顿第二定律，粒子可以通过力量或冲动由内关节和外力施加（碰撞,重力、空气阻力、风力等）。

Self-collision of the particles and collisions between different rope bodies are not calculated. However, the rope interacts with environment by colliding with other physical bodies if the Collision box is checked. Its behavior in case of contact is controlled by such parameters as friction and restitution. Selective physical interaction is available via corresponding bitmasks.不计算粒子的自碰撞和不同绳体之间的碰撞。但是，如果选中 Collision 框，绳索会通过与其他物理物体碰撞来与环境相互作用。它在接触情况下的行为由以下参数控制摩擦和归还.选择性的物理交互可通过相应的位掩码.

Thus, Rope body can be regarded as a constrained system of rigid particles and therefore shares some parameters with Rigid body:因此，Rope body 可以被视为刚性粒子的约束系统，因此与 Rigid body 共享一些参数：

• Mass
• Friction
• Restitution
• Linear Damping and Angular Damping

Particle Radius粒子半径#

As it was already mentioned, each particle is a sphere with a set radius. Thus, particles use continuous collision detection. The rope never lies flat on the ground or tightly adheres to the surfaces. There is always a gap equal to particle radius.正如已经提到的，每个粒子都是一个具有设定半径的球体。因此，粒子使用连续碰撞检测.绳子永远不会平放在地上或紧紧地粘在表面上。总是有一个等于粒子半径的间隙。

As collisions between the particles are not calculated, they should not be considered when setting a radius:由于不计算粒子之间的碰撞，因此在设置半径时不应考虑它们：

• Higher values are preferable for more robust behavior. However, too big radius may result in incorrect interaction with the environment (twitching or blowing up of the rope).对于更稳健的行为，更高的值更可取。但是，太大的半径可能会导致与环境的不正确交互（绳索抽搐或炸毁）。
• Lower values decrease the gap between the Rope body and the surface. However, too low radius results in poor collision handling.较低的值会减少 Rope body 和表面之间的间隙。但是，半径太小会导致碰撞处理不佳。

注意

An object can pass through the rope, when the particle radius is small and the rope is stretched. The reason is that continuous collision detection is performed only for particle spheres located in vertices of rope mesh.物体可以通过绳子，当粒子半径很小，绳子是拉伸.原因是仅对位于绳网顶点的粒子球体进行连续碰撞检测。

Joints Solver Iterations关节求解器迭代#

A rope may be deformed by stretching and folding. These deformations are controlled with joint constraints of two types:绳索可能会因拉伸和折叠而变形。这些变形由两种类型的关节约束控制：

• Linear restitution controls stretching.线性恢复控制拉伸。
• Angular restitution controls folding.角度恢复控制折叠。

With these types of constraints, it is possible to obtain the desired look and feel of the rope and simulate a variety of different deformable materials ranging from a stiff metal wire to an elastic rubber cord.通过这些类型的约束，可以获得所需的绳索外观和感觉，并模拟各种不同的可变形材料，从硬金属线到弹性橡胶绳。

Linear Restitution线性恢复#

Angular Restitution角度恢复#

The Rigidity parameter is an additional constraint of the rope motion to make it stiffer and more inflexible. For that purpose, linear and angular velocities of each rope particle are corrected according to the total velocities interpolated for all the particles.Rigidity 参数是绳索运动的附加约束，使其更硬和更不灵活。为此，每个绳索粒子的线速度和角速度根据为所有粒子插值的总速度进行校正。

• The minimum value of 0, makes the rope elastic, flexible and easily deformable.0 的最小值，使绳索有弹性、柔韧且容易变形。
• The maximum value of 1, makes the rope stiffer and less prone to deformation.1 的最大值，使绳索更硬，不易变形。

When the rope is stretched or folded beyond its elastic limit, it tears and shreds into pieces. Tearing is caused by applying the force or collision with a physical body, and depends on the rope stiffness (controlled by linear and angular restitution parameters). The rope is torn only along the edges of rope triangles, splitting mesh vertices and duplicating particles.当绳索被拉伸或折叠超过其弹性极限时，它会撕裂并撕成碎片。撕裂是由施加力或与物理身体碰撞引起的，取决于绳索的刚度（由控制线性和角度恢复参数）。绳索仅沿绳索三角形的边缘撕裂，分裂网格顶点并复制粒子。

注意

If torn pieces of rope fall onto one plane, they cause Z-fighting.如果撕裂的绳子掉在一个平面上，它们会引起 Z-fighting。

Linear Threshold Distance线性阈值距离#

Angular Threshold Angle角度阈值角度#

Updating each frame a huge number of objects located far away from the camera that are hardly distinguishable or observed as a mass is a waste of resources.更新每一帧远离相机的大量物体，这些物体几乎无法区分或观察为质量是一种资源浪费。

To improve performance and avoid the excessive load, simulation of the rope can be updated with a reduced framerate. When the player is out of the area specified by the Update Distance Limit, the rope stops to be updated and freezes statically.为了提高性能并避免过度负载，可以对绳索进行模拟更新了降低的帧率.当玩家离开 Update Distance Limit 指定的区域时，绳索停止更新并静态冻结。

The set of frame rates given below enables you to specify how often the rope simulation should be updated when the object is visible, when only its shadow is visible, or when it is not visible at all.下面给出的一组帧速率使您能够指定在对象可见、仅其阴影可见或根本不可见时应更新绳索模拟的频率。

Parameters -> Physics tab -> Periodic Update sectionParameters -> Physics 选项卡 → Periodic Update 部分

FPS When Object Is Rendered To Viewport	Update rate value for the case when the object is rendered to viewport.对象渲染到视口时的更新速率值。
FPS When Only Object Shadows Are Rendered	Update rate value when the object itself is outside the viewing frustum, and only its shadow is rendered to viewport.当对象本身在视锥体之外时更新速率值，并且只有它的阴影被渲染到视口。
FPS When Object Is Not Rendered At All	Update rate value when both the object and its shadow are not rendered to the viewport.当对象及其阴影都未渲染到视口时更新速率值。
Update Distance Limit	Distance from the camera up to which the object should be updated.对象应更新到的距离相机的距离。

注意

These values are not fixed and can be adjusted by the Engine at any time to ensure best performance.这些值不是固定的，引擎可以随时调整以确保最佳性能。

This feature is enabled with default settings ensuring optimum performance and can be adjusted per-object in the UnigineEditor or via API at run time.此功能使用默认设置启用，可确保最佳性能，并且可以在 UnigineEditor 中或通过 API 在运行时针对每个对象进行调整。

警告

Be aware that using reduced update frame rate for an object should be carefully considered in your application's logic, as it may lead to various issues with rendering Mesh Skinned and Mesh Dynamic (flickering due to misalignment, e.g. in case of attaching a rope to a Mesh Skinned).请注意，在应用程序的逻辑中应仔细考虑对对象使用降低的更新帧速率，因为这可能会导致渲染 Mesh Skinned 和 Mesh Dynamic 的各种问题（由于未对齐而闪烁，例如在将绳索连接到 Mesh Skinned 的情况下）。

To assign a Rope body to an object via UnigineEditor perform the following steps:通过将 Rope body 分配给对象统一编辑器执行以下步骤：

1. Open the World Hierarchy window.打开 World Hierarchy 窗口。

2. Select a dynamic mesh object to assign a Rope body to.选择一个动态网格要为其分配 Rope body 的对象。

   注意

   Make sure that the object's mesh meets requirements!确保对象的网格满足要求！

3. Go to the Physics tab in the Parameters window and assign a physical body to the selected object by selecting Body -> Rope.转到 Parameters 窗口中的 Physics 选项卡并分配一个物理身体通过选择 Body -> Rope 到选定的对象。

   

4. Set the body's name and change other parameters, if necessary.如有必要，设置主体的名称并更改其他参数。

Rope attached to animated character连接到动画角色的绳索

Ropes can be attached to the following types of bodies:绳索可以连接到以下类型的身体：

• Rigid body
• RagDoll body
• Dummy body

To attach a rope to a body, use the Particles joint. In case of Rigid body (either static or dynamic) and Dummy body, pinned particles stay fixed in their position and follow transformations of attached objects pulling the rope with it.要将绳索连接到身体，请使用 Particles joint。在 Rigid body（静态或动态）和 Dummy body 的情况下，固定粒子保持固定在它们的位置，并跟随用它拉动绳索的附加对象的变换。

1. Select Rigid body, RagDoll body or Dummy body.选择 Rigid body, RagDoll body 或 Dummy body。
2. Add Particles joint.添加 Particles joint。
3. Specify Rope body.指定 Rope body。
4. Adjust the pinning area using the Threshold and Size parameters of the Particles joint.使用 Particles joint 的 Threshold 和 Size 参数调整固定区域。

注意

To ensure stable simulation it is important to set appropriate masses of the rope and the attached body. Unbalanced masses may cause twitching of rope joints.为了确保稳定的模拟，重要的是设置适当的绳索和附着体的质量。不平衡的质量可能会导致绳索接头抽搐。

Attachment to Skinned Mesh附加到蒙皮网格#

Convincing simulation of the rope on a Mesh Skinned character requires a different approach. To follow bones transformations, each vertex of the rope that is found in the Particles joint area is mapped to the nearest Mesh Skinned vertex (up to the distance specified by the Threshold parameter of the particles joint).令人信服的模拟 Mesh Skinned 角色上的绳索需要不同的方法。为了跟随骨骼变换，在 Particles joint 区域中找到的绳索的每个顶点都映射到最近的 Mesh Skinned 顶点（最多由粒子关节的 Threshold 参数指定的距离）。

注意

It is not recommended to attach the rope directly to the Mesh Skinned character, because difference in topologies may result in visual artifacts. Instead, it is better to create an identical rope surface on the Mesh Skinned character, make it invisible and attach a physical rope to it.不建议将绳索直接连接到 Mesh Skinned 字符，因为拓扑不同可能会导致视觉伪影。相反，最好在 Mesh Skinned 角色上创建一个相同的绳索表面，使其不可见并在其上附加一条物理绳索。

For example, we need to create a rope that is glued to the hand of a Mesh Skinned character while the rest of the rope hangs and moves loosely. It is done in the following steps:例如，我们需要创建一根绳子，它粘在 Mesh Skinned 角色的手上，而绳子的其余部分则悬垂并松散地移动。它是通过以下步骤完成的：

1. When creating a Mesh Skinned, add a rope segment surface identical to the clipped part that needs to be pinned. In our case, it's the rope part in a hand.创建 Mesh Skinned 时，添加与需要固定的剪裁部分相同的绳段表面。在我们的例子中，它是手中的绳索部分。
2. Add Mesh Skinned that has a RagDoll body assigned. Make sure that the rope segment surface is enabled.添加 Mesh Skinned 具有布娃娃分配的机构。确保启用绳段表面。
3. Add a separate dynamic rope mesh and synchronize its position with Mesh Skinned character. Turn off physical simulation (CTRL + SPACE) and assign a Rope body.添加单独的动态绳索网格并将其位置与 Mesh Skinned 角色同步。关闭物理模拟 (CTRL + SPACE) 和分配Rope body。
4. Attach Rope body to RagDoll body. If the Threshold distance of the particles joint is set low enough, the physical rope will be automatically attached only to the rope segment surface (i.e. hand). After that, the rope segment surface is simply disabled and does not provide any load at all.附Rope body 到 RagDoll body。如果粒子关节的 Threshold 距离设置得足够低，则物理绳索将自动仅附加到绳索段表面（即手）。之后，绳段表面被简单地禁用并且根本不提供任何负载。