Sketcher: Constraint based sketch vs. sketch operations

topsolid-tips-and-tricksWhen working with a 3d solid modeling solution like TopSolid, it is very important that you understand how its sketcher functions.  Most 3d modeling solutions have one way to create and work with sketches.  And that one way is supposed to fit every need you have.

The Problem

The problem with that notion is that your needs change all of the time.  The way you define geometry within a sketch needs to be completely flexible.  What do I mean? Sometimes you may want to create a simple sketch, while other times you may want to create a really intelligent sketch. Perhaps you want to create a sketch that allows you to apply operations to it that really allow you to capture your design intent more cleanly.  Thankfully for you, you use TopSolid and have the freedom to do both.

Understanding a sketcher

Let’s start by understanding what a sketcher is first.  A sketcher allows you to create wire-frame based geometry. In TopSolid there is a 2d Sketcher and a 3d Sketcher. For this discussion, we will be focusing on the 2d sketcher.

Different types of TopSolid sketcher constraints A 2d sketcher allows you to create wire-frame on a specific plane. The sketcher environment at the solving level, allows you to define the sketch using dimensional relationships as well as geometric relationships.  These are known as constraints.  In the image to the right, you will see a sample of a constrained sketch.  This image shows both dimensional and geometric constraints.

At the solving level of a sketch you can do many things. There are options to create lines, arcs, splines, ellipses and so on. You can apply fillets to sharp corners. You can of course trim one segment by another or even one profile by another profile.  There are literally an infinite number of ways to create your sketch.

Now enter into another level of the sketcher. We call it a sketch operation.  A sketch operation allows you to apply re-calculable operations to the sketch.  What this means is that every single modification made to the underlying sketch will then cause all of the secondary operations to recalculate. TopSolid offers a plethora of sketch operations. You should be sure to explore each of them.

In the image below, you see the history tree in TopSolid known as the Operations Manager.  Remember, in TopSolid, the history tree is inverted. This means that the first step is at the bottom of the tree and the most recent at the top. This allows quicker access to recently created features that you are still editing.

Sketch Operations inside of TopSolid's sketcherThis image shows you the solving level sketch first followed by the sketch operations that are being applied.  Thus, when you rebuild after modifying the main solving level sketch, all of the operations to that sketch recalculate. Sketch operations are designed to make your sketches smarter as well as more update-able.  Most importantly, they are designed to simple work and to save you a lot of time.

Does this make sense?  I venture to say that this probably is a bit confusing. After all what I am describing here does not exist in any other software on the market.  Because of this, it may be hard to wrap your brain around this.  And guess what? That’s OK!

To help you better understand the main difference between a solving level sketch and a sketch with operations applied to it, I have created the following video.  This video gives you a side by side comparison between the two modes. In fact I create the same basic profile using both modes. Then I simply make a design change.

In the design change that only uses the standard sketcher, you will see me have to take many steps to implement my change.

IN the design change where I used sketch operations, you will see…well something fantastic.  You will see that, in fact I do far less work to implement my change.

So circling back to the beginning of this post, where I spoke about flexibility within a sketcher being important.  The goal of this is that after watching this video, you have opened your mind up a bit to the possibility of making your sketches just a bit more intelligent. And by doing so, you make your work a bit more efficient. And by gaining in efficiency…well, I’ll let you fill in the blanks on this one.

 

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About Bill Genc

Technical Director at Missler Software, Inc. It is my job to make sure that you can do your job with the TopSolid solution!