Page 312 - Mastering SolidWorks

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284 CHAPTER 9 PAtterning And Mirroring

You might hear a lot of conflicting information about which features are better to use in
different situations. Users coming from a 2D background often use a function such as sketch
patterning because it’s familiar, without questioning whether a better approach is available, and
often without having a way of measuring how it performs. When in doubt, you can perform a
test to determine which features work best for a given situation.
To compare the performances of various types of patterns, I made a series of 20 × 20 patterns
using circles, squares, and hexagons. The patterns are both sketch patterns and feature patterns,
and I created them with both Verification On Rebuild and Geometry Pattern turned on and off.
Verification On Rebuild is an error-checking setting that you can access through Tools ➢
Options ➢ Performance. Geometry Pattern is a setting that is applicable only to feature patterns,
and it disables the intelligence in patterned features.
Table 9.1 shows the rebuild times (in seconds) of solid geometry created from various types of
patterns as measured by Performance Evaluation. (It is found at Tools ➢ Evaluate ➢ Performance
Evaluation; this was formerly called Feature Statistics.) Sketch patterns are far slower than
feature patterns, by a factor of about 10. The biggest speed reduction occurs when you use sketch
patterns in conjunction with the Verification On Rebuild setting, especially as the number of
sketch entities being patterned increases.

Verification on Rebuild
When the Verification on rebuild (Vor) setting is turned off, a given face is tested against each of
its neighbors (for example, to see if the model is self-intersecting). When it is turned on, Vor tests
each face against every other face in the model. on a simple cube, the difference between on and off
is four tests versus five tests. on a larger model, it could well be the difference between four tests
and a thousand tests. the type of error this would catch would be, for example, if you had a box and
shelled it out, removing one face, and then you put a large fillet on an outer edge. You would see the
inside of the shell break through the outside of the fillet. if Vor were turned on, this would cause
an error. if Vor were turned off, SolidWorks would allow this, and you would have invalid geometry
with no error. to examine this in more detail, open the sample model Chapter 9 - VOR.sldprt.
of course, having Vor turned on for large models is very costly from a performance point of view.

Generally, the number of faces and sketch relations being patterned has a significant effect on
the speed of the pattern. The sketch pattern times are taken for the entire finished model,