Select the interior surface of three-dimensional shapes using selection layer view

 In three-dimensional CAE simulation analysis, it is often necessary to select interior surfaces of geometric bodies or choose surfaces that are occluded. This is applicable when setting up contact conditions for complex assemblies in structural analysis, defining boundary conditions for inner surfaces in electromagnetic, fluid, or thermal analyses, among other scenarios. Such requirements pose significant demands on the pre-processing modules of engineering simulation software.

Currently, a common approach in the industry is to add a selection layer view in a small region within the 3D graphics window. This feature displays the selection layers after clicking on a geometric body, enabling the user to modify the desired surfaces. This method is simple, intuitive, and provides a good user experience. However, this service adds extra software development work, as it requires incorporating an additional viewport in the 3D window. When implementing a selection layer view, the impact the feature has on the overall software performance must also be payed attention to.

Selection layer view

In the model below, there is a sphere with two small spherical cavities inside. When the model is set to be semi-transparent, the positions and sizes of the internal cavities can be observed. In 3D electromagnetic analysis, the exterior surface is often set as the far-field boundary, and various excitations are applied to the inner surface, such as voltage. Similarly, in fluid and thermal analysis, certain boundary conditions are set for the inner surface. In such cases, the GUI operation needs to be able to select the interior surfaces of the sphere.

When clicking on the position of the internal spherical cavity, the default outermost surface is selected and highlighted in green. If there are more optional surfaces, the layer view will be displayed. At this point, the layer view shows two layers: the unselected inner surface on the left, represented in gray; the selected outer surface on the right, highlighted in green.

Moving the mouse to the left side of the layer view automatically selects the left layer. Now, the model updates the selected surface shown - the inner surface is now selected and highlighted in green.

The layer view simplifies the process of selecting inner surfaces. In this example, a spherical model demonstrates how to select the inner surfaces of 3D geometric bodies. The video demonstration is as follows:

This method is correspondingly applicable to other types of geometric bodies. When the position of the mouse click involves multiple surfaces, the layer view will display the corresponding number of layers. If the position involves fewer than two surfaces, the layer view remains hidden.

The layer view is a new feature introduced in the WELSIM 2024R1 version, primarily aimed at enhancing the pre-processing capabilities in three-dimensional fluid and electromagnetic simulations.

图层演示器用于三维实体内表面的选择

在三维模型CAE仿真分析中，我们常需要选择几何体的内表面，或者选择被遮挡的表面。如结构分析时复杂装配体的接触设置，电磁、流体或热分析时内表面的边界条件等。这对工程仿真软件的前处理模块提出了比较高的要求。

目前，业界比较常见的方式是：在三维图形窗口中的一个小区域增加图层演示器，允许用户在点选几何体后，显示图层演示器，此时用户可以更改所需要的表面。这种方式简单直观，用户体验好。然而增加了额外的软件开发工作，需要在三维窗口中增加一个额外视图。增加此功能时，也需要注意对软件整体性能的影响。

图层演示器示例

下图模型是一个球体，内部含有两个小的球体空腔，当设置模型为半透明时，可以看到内部的球体空腔位置与大小。在三维电磁场分析时，我们常会将外表面设置为远场边界，内表面设置各种激励，如电压等。类似的，流体与热分析中，内表面也会设置某种边界条件。此时GUI操作就需要能够选中球形内表面。

当点击内部球体空腔位置时，会选中默认的最外层表面，并以绿色高亮显示。如有额外的可选表面时，图层演示器会显示出来。此时，图层演示器显示两个图层，左边是未选中的内表面，以灰色表示，右边是选中的外表面，以绿色高亮表示。

将鼠标移动至图层演示器的的左边，就会自动选择左边的图层，同时模型会更新所选中的表面，内表面被选中，并以绿色高亮显示。

图层演示器使得选择内表面变得简单。本例通过一个圆球演示如何选取三维几何体内表面。视频演示如下：

对于其他类型的几何体，此方法同样适用。当鼠标的点击位置含有多个表面，图层演示器会显示相应数量的图层。而当点击位置少于两个表面，则不会显示图层演示器。

图层演示器是WELSIM 2024R1版本中新添加的功能，主要用于增强在三维流体和电磁仿真中的前处理能力。