Geometry Pattern Myth

Matt,

Good detective work. I must admit, I never turn on "geometry pattern" unless the feature fails. Interestingly, you get the impression Solidworks actually know that it is faster with it switched off, because that is the default setting.....

You repeated what I've heard others say regarding sketch patterns being slower than feature patterns. Do you know whether this also applies to "sketch driven patterns"?

Regards, John Harland

I haven't tested that directly, but I would suspect that sketch driven patterns would behave like feature patterns rather than like sketch patterns. The important part is the way faces are created. Sketch pattern creates faces the same way a regular extrude creates them. Sketch driven pattern creates faces the same way a linear pattern creates the faces.

Geometry patter does, in some instances, have its place as a performance benefit. I'd not actually tested it since 2006 first came out until you posted.

Bit of history: When 2006 came out I tested, then after a month or so, upgraded all our files. Worked fine until I noticed that certain assembly drawings were taking an inordinate amount of time to rebuild if any change was made. Tracked it down to pieces of perforated tubing, drawn with actual perforations ( I now draw plain tubing, annotate, and apply a material to create the illusion of perforations ). Rebuild times for these relatively simple parts could take nearly an hour in 2006. I tracked it down to some sort of funtionality change/bug made to how geometry pattern worked. The parts had origionally been drawn in 2001-2005 without long rebuilds, so I had not used geometry pattern. Editing the parts and enabling geometry pattern in 2006 brought the rebuild times back to what they'd been in 2005. I submitted it as a bug to my var, who claimed that it was "working as intended" so would not submit a bug report. Fine, I sent them the remainder of similar parts that I had and told them to convert them to 2006. Got them back after a week or so. It was taking 4-5 hours of cpu time to edit each pattern and enable geometry patterns for a given file.

Looks like 2007 is working similar to what 2005 did. Here is the part that I just tested ( 2007 sp1 ). Its a 2" diameter tubing with 1330 3/16" holes in it. It consists of the following features: sheet metal, lofted bend, cut-extrude1 ( seed hole for linear pattern ), linear pattern1 ( 35 instances along the tubes axis ), cut-extrude2, linear pattern2 ( 36 instances ), and circular pattern1 ( 19 copies of the two linear patterns ). No holes extend beyond the end of the tubing ( which might cause the geometry changes that Matt referred to ).

Starting condition is that geometry pattern is checked for all patterns. VOR is off for all CTL-Q rebuilds. I then unchecked geometry pattern in each feature, one at a time, and noted rebuild times. I then re-enabled it for the circular pattern, to double check.

geometry pattern on for all patterns- 49.25, 50.89 seconds off for linear pattern1- 54.28,53.52 off for linear pattern2- 52.47,51.33 off for circular pattern-62.42,62.06 on for circular pattern-56.52,54.97

Its pretty clear to me that, at least the circular pattern, benefits in performance from using the geometry pattern option.

I think what is missing from SW is an ACCURATE explanation of what geometry pattern does, when its applicable, ect. Instead I think they are giving out information based upon what they would like it to do. It does not seem to perform the same release to release.

I'd be happy to send Matt the file that I tested, if he wants it. Maybe he'll see something that I missed. Sorry if this is a bit verbose, after last years fiasco, patterns became kind of a sore spot for me.

Brian,

Yeah, I wouldn't mind taking a look at the parts.

Your post prompted me to take a closer look at end conditions which turn out to be very important. I used the same part, a rectangular block with a 20x20 pattern of cut-extruded circle, instances don't intersect with anything but the flat plate.

no GP GP offset from surf 2.88 .91 up to surf 2.70 .89 through all .20 .28 blind .08 .27 up to next .08 .28

This says that you pay a big price for using up to and offset from surface end conditions and that GP shows some performance benefits for those end conditions, but remember that those are intelligent end conditions that make each instance of the pattern different, and GP essentially makes them all the same. (see help for example). So for these examples, unless the up to and offset from end conditions are being used when they don't need to be, GP can't be said to produce a performance benefit, since the finished geometry is different.

In my examples previously I had used the through all end condition, which suffers about a 30-40% hit by using GP.

What is big news to me is that using blind and up to next offers a 60% time savings over through all, and take a 300%+ hit from GP. I'm glad I did this additional test.

So, I believe your results indicate that you may be using one of the first end conditions. If this is true, you will get a bigger benefit out of using blind or up to next than you will from Geometry Pattern. An interesting thing here is that the up to next condition is still an intelligent end condition, but the speed cost of using it is very low. I have a new default end condition for patterns, I think.

Can you say what the end conditions are on the patterned features in your parts?

My end conditions are "thru all". I'll send you the part to look through. But if you really want to see a huge difference, and still have it loaded, re-create the part in 2006 ( one of the earlier sps ).