ZW3D Tip:Creating Multilateral Surfaces

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ZW3D Tip:Creating Multilateral Surfaces

Free form surfaces in ZW3D allow designers and engineers to quickly create extremely accurate designs through free shape and surface functions. These forms give products unique aesthetic feelings based on the emotions of designers, who are therefore not limited by the rigid functions found in traditional CAD software.

One aspect of free form surfacing is the multilateral surface, which refers faces with more than four edges, especially those with an odd number of edges. In surface-modeled designs, multilateral surfaces are very common, and so it is useful to learn how to create multilateral surfaces of high quality. Let’s look at several approaches available in ZW3D, including n-sided patches, FEM (finite element method) patches, and edit multilateral surfaces.

1. Making N-sided Patches

In ZW3D, we can use then-sided patch function to create faces by patching three or more profiles, as shown by figure 1.


Figure 1: Creating an n-sidedpatch from four profiles

The quality of the resulting surface is, however, poor, because the patch is composed from several smallmulti surfaces. Let’s try something different.

 2. FEM Patches

The FEM Patch command fits a single face through a set of points posited on boundary curves. This is similar to the n-sided patch, but with one important difference: instead of first subdividing the patch into four-sided NURBS faces, the surface is fitted directly on the boundary curves through a collection of points, and then trimmed along the boundary, as shown by figure 2.



Figure 2: Creating a FEM patch from the same four profiles

This method produces favorable results for cases in which creating well-formed four-sided patches would otherwise be problematic, such as when the input curves resemble the outline of a clover leaf. (N-sided patches cannot handle cases where the boundary edges include concave curves.)

The drawback to FEM patches, however, is that they provide poor control over the shape of the inner surface. So, to create multilateral surfacesof high quality and with controllable shapes, it’s best to use the method I describe next.

3. Multilateral SurfacesfromFour AngledSurfaces

To create multilateral surfaces, follow these steps:

a. Draw new curves tangent to the original ones, with which we can create a basic forth-angle surface, as shown in figure 3.Notice that controlling continuity tangency is a key option.

Figure 3: Creating blend curves

b. To create amirrored shape and keep it tangent, we need to create assistant faces. Do this by extrudingthem along the direction of mirror plane, as shown by figure 4.


Figure 4: Creating the basic surface

c. Trim the surfacesto get the four edges. The trim points must shorter than the tangent points of the curves just created. (See figure 5.) 


Figure 5: Trimming back thesurface

d. Create the second surface, and then finish the complete shape. (See figure 6.)


Figure 6: The final result

We can use a variety of operations to create multilateral surfaces with the same technique.


Figure 7: Variety of modeling procedures to arrive at the same shape

ZW3D provide a variety of tools to meet the needs of designers of multilateral surface models. This flexibility lets us design according to the actual requirements, and so choose the best method, the most reasonable design, and create a high quality surface.

With ZW3D, you design accurate surfaces to get meticulous drawings ready for manufacturing. Better yet, it allows you to keep the connections complete for modification at any time. This allows designers to have confidence in researching different designs methods, and so create beautiful products -- which result in increased sales. 

About ZW3D

ZW3Dis all-in-one, affordable CAD/CAM system that enables concept-to-finished-product-design in an integrated, collaborative environment. The proprietary Overdrive™ kernel delivers 3D part and assembly modeling, 2D production drawings, reverse engineering, motion simulation, mold design and integrated CNC machining. It simplifies the design process, from concept to completion. To experience ZW3D 2012, where the only limit is your imagination, please go to to download your free 30-day trial today.


Short Description

ZW3D provide variety of tools to meet the design of the multilateral surface models. It lets you design according to the actual requirements, and so choose the best method, the most reasonable design, and create a high quality surface.



ZW3D,,CAD/CAM, Modeling, Surfacing,Multilateral Surfaces

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Author’s Name:

ZWCAD Software Co., Ltd


Author’s Info:

A CAD/CAM Specialist