Default Controls

When specifying custom values, this node is added to the Custom Controls > [Surface] > Controls node.

In the above diagram, the black and blue boundaries represent surfaces from which subsurfaces are generated. The dotted magenta line represents the subsurface that would have been produced without the concave angle limit being activated. With the concave angle specified to a suitable value (that is, more than the geometry interior angle), the red line represents the retracted subsurface, which results in a higher-quality prism layer mesh.

In the above diagram, the blue boundary represents the boundary surface from which a subsurface is generated. The dotted magenta line represents the subsurface that would have been produced without the convex angle limit being activated. With the convex angle specified to a suitable angle (less than the exterior angle of the geometry), the red line represents the retracted subsurface, which results in a higher-quality prism layer mesh.

The Near Core Layer Aspect Ratio controls the ratio between the cell height (layer thickness) and cell width of the prism cell layer closest to the core mesh. The cell faces on the core mesh (known as the subsurface) govern the prism layer cell width, and so the layer height is adjusted to set the aspect ratio. When the geometry surface is curved, the Surface Curvature control refines the mesh, which results in smaller cell widths across the curved portion. The near core layer aspect ratio becomes effective on these curved portions, as it prevents the mesher from generating long, thin cells with a high aspect ratio.

This property only affects the thickness of the cell layer that is next to the core mesh. The thickness of the remaining layers is defined according to the stretching mode and function, and with any other active constraints.

The near core layer aspect ratio is illustrated in the diagram below. The red area represents the prism layer closest to the core mesh (that is, the core mesh begins after the red line). The dashed magenta line shows the profile of the prism layer if no aspect ratio is applied.

As shown above, the aspect ratio is defined as the layer thickness divided by the cell width. For example, setting a value of 2 gives a layer thickness twice as large as the cell width. To deactivate the property, set a value of 0.

The Near Core Layer Aspect Ratio is different to the Advancing Layer Mesher Limit Aspect Ratio (see Advancing Layer Mesher Reference), which stops building prism layers when the specified aspect ratio limit is reached, whereas the near core layer aspect ratio can modify the total thickness. For best results, activate the Enhanced Quality Triangle option in the surface remesher (see Surface Remesher Reference). Enhanced quality triangles provide better surface size consistency which results in smoother aspect ratio changes in the prism cells.

Using an aspect ratio improves the transition from the prism cell layers to the core mesh, as the prism layer cells are a similar size to the core mesh cells. This option also prevents “tall” cells being generated, as the aspect ratio of prism layer cells is explicitly specified. Setting the near core layer aspect ratio influences the overall prism layer thickness, particularly on curved surfaces. However, note that the overall prism layer thickness always remains at or below the user-defined value.

As an example, the following image shows a thick boundary layer without the near core layer aspect ratio specified. There are high aspect ratio cells in the prism layer due to the curvature of the geometry and associated increased surface mesh density.

If the near core layer aspect ratio is set to 1, the transition from the prism layer to the core volume mesh is greatly improved. The volume of the prism layer cells is then closer to the volume of the adjacent core mesh cells.

The overall prism layer thickness is reduced in this example. A more uniform thickness would be obtained by increasing the number cell layers, as shown below. You could also increase the specified aspect ratio.

This feature, along with the Near Core Layer Aspect Ratio option, is designed to help you generate smoother cell volume transitions between the trimmed and prism layer meshes. It is set by activating the Limit Cell Size by Prism Layer Thickness property.

In order to produce a volume mesh containing pure tetrahedral and prismatic cells only, the generate standard cells option can be used with the tetrahedral meshing model only. This ensures the number of prism layers used in the mesh is uniform throughout. That is, no custom number of prism layers have been set for part surfaces, regions, or boundaries. If these conditions are met, then the volume mesh that is produced can be exported to third-party packages that can only accept standard cell shapes. The default state for this option is off.