Thursday, March 31, 2011

Sketch Constraints and the Eyeballing Game (slightly Inventor related fun)

If you've used Inventor for any length of time you've probably started to develop a "good eye" for sketching geometry at a relative proportion or scale. Sometimes when I apply dimensions to my sketch, I impress myself by just how accurately I've managed to get the sketch by just "eye-balling" it. Other times I'm not even close, though. Often times I purposely sketch things off center or skewed in one way or another, so that it is obvious to me what dimensions or sketch constraints I need to apply.

If you're a new Inventor user you might be employing the "eye-balling" approach inadvertently when you leave your sketches under constrained and/or under dimensioned. Of course this is not a good way to create sketches in Inventor (see: Inventor 101: Simple Fully Constrained Sketches), and you should (almost) always strive for a fully dimensioned and constrained sketch.

With these things in mind, I thought I'd share a link that provides a fun way to practice your "eye-balling" skills, and will likely make you more appreciative of your Inventor sketch constraints and dimensions.

The Eyeballing Game from, prompts you to adjust a set of geometry for a given condition. For instance here the goal is to drag the lower left corner to make a parallelogram. The blue lines show my attempt, the green shows the correct position:

In Inventor I'd simply place parallel constraints to achieve this:

 Here was my attempt at setting a point equidistant to the edges of the triangle:

In Inventor I'd create a construction circle and then apply tangent constraints:

Here is my attempt at bisecting an angle:

In Inventor I'd add a symmetric constraint (or add angle dimensions):

Have a go at the The Eyeballing Game and you'll likely come away with an higher appreciation for sketch constraints and dimensions.