What is Layer Reduction?

The Layer Reduction Percentage property controls the point at which the number of layers within a contracting prism layer is reduced.

When generating a prism layer mesh, it can become necessary for the mesher to reduce the overall prism layer thickness due to corners, narrowing gaps, curved surfaces, or other local geometry. In these cases, it is preferable to reduce the number of layers locally as the thickness decreases, maintaining a lower aspect ratio (and hence better quality) for the remaining prism layer cells. The Layer Reduction Percentage property controls the point at which the number of layers within a contracting prism layer is reduced.

By default, the Layer Reduction Percentage is specified as a percentage of the global prism layer thickness value. Specifying a value between 0% and 100% activates the feature and the layer reduction thickness is calculated as:

Layer Reduction Thickness=  Layer Reduction Percentage100⁢× Prism Layer Thickness

If a prism layer thickness has been specified on a part surface, region, or boundary, or through a volumetric control, then this local value is used instead of the global value.

Wherever the prism layer thickness falls below the Layer Reduction Thickness, prism layers are naturally thinned out as the prism layer thickness reduces. The default Layer Reduction Percentage value is 50%, which means that when the prism layer is reduced to half its target thickness, layers begin to be removed. Setting Layer Reduction Percentage to 0% deactivates the feature.

The range of influence of the layer reduction scheme on the prism layer mesh is illustrated below:

In the diagram that is shown above, the prism layers corresponding to the blue shaded areas would be subject to prism layer reduction based on the layer reduction thickness value as drawn. As this value increases, more of the prism layer is subject to the reduction process.

A comparison of a prism layer mesh without layer reduction and with layer reduction is shown below:



In the above example, no layer reduction (that is, layer reduction percentage = 0) has been applied. As the subsurface becomes thinner towards the angled corner, the prism layers progressively get thinner and eventually truncate where the subsurface retracts to zero height (determined by the minimum thickness value).

With a layer reduction value applied, the above situation can be avoided, as shown below:



In this case, the prism layers start truncating as you move towards the angled corner, reducing the number of layers that remain and increasing the overall quality.

Notes:

  • The layer reduction feature has no effect where there is only one prism layer.
  • If a layer reduction percentage value of 100% is used, then the entire prism layer mesh is subject to layer reduction. In general, values of 25 - 75% are reasonable to use for most cases.
  • If the option is used with a volumetric control, then the prism layers that are associated with the control shape are also subject to layer reduction in the same way as described above.