Hints & Tips

For this newsletter we will take a look at some of the common questions asked where answers are not so obvious. During the training courses, many of these questions are explained but for those who have been unable to attend....

Ruled / Extruded Surface - Curve Optimisation

Creating a ruled or extruded surface is a very simple operation, but one where the quality of the resulting surface can depend heavily on the original curve or edge data. When working with imported data, it is relatively common to find surfaces that have polyline edges. Generally this is not a problem, however, if it is necessary to build additional geometry from the original edge data, it can be beneficial to clean the construction conditions to improve the data result for future CAD operations.

Polyline edge trimming can create multiple edges/elements at the edge of a surface

The image above shows how polyline trimming has created a scenario where the edge of the surface is a collection of a number of smaller edges. While this does not cause a particular problem, it is important to understand that for future operations (blending for example), the simplicity of the face will improve the chance of success.

A concatenated curve will create a combined surface of multiple faces if the curve in not cleaned

In the case where we have a number of polyline edges, it is often easier to extract wireframe edge geometry and concatenate the data to create a single curve. In the image above, although a single curve has been created, the resulting surface is still created as a set of single faces. The reason for this result is that the curve still has 'concatenation' or 'knot' points. For example, if you consider tying two pieces of rope together, the knot is present where the two pieces join. This knot point exists in the concatenated curve and is retained when a surface is created. To overcome this situation, it is necessary to reprocess the curve and remove any 'concatenation' or 'knot' points. This is achieved using the function WIREFRMAE > EDIR CURVES > REPROCESS CURVE.

Reprocessing the curve to remove the knot and corner points will create a single curve and a single face

The image above shows the Reprocess Curve dialog. From here it is possible to perform a number of operations to improve the curve makeup. Please note that is it possible to setup a set of operations (Composed commands), that can be performed on a curve as a single function. This can greatly simplify curve editing. In this example, the 'concatenation' or 'knot' points have been removed (Please note that the No. Concatenations / No. Corners parameter has been changed from 4 to 0. However, please also consider the effect of removing corners in a curve that us supposed to have a sharp corner). With this cleaned curve, any resulting surface will be constructed as a single face and should be easier to manipulate in later operations..

This concept of curve editing is also very important when creating ruled surfaces where the connecting edges are not compatible. Using the options within the WIREFRMAE > EDIR CURVES > REPROCESS CURVE dialog, it is possible to edit all parameters including the number of vertices within the curve. If you are creating a ruled surface between two curves, the best result should be achieved from a set of curves with the same number of vertices. In this case, the numbers can be matched, but it is important to take the highest number. Reducing the number of vertices can alter the shape of a curve.

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If you have any tips or tricks that you would like to share, please email me with a short description (marc@vero.co.uk) and I will include them within a future Vero Newsletter.

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