Autodesk Inventor surfacing. An introduction to Surface continuity

Thanks very much to David Harrington, John Evans and the team at AUGIworld for allowing me to re-publish this article. To read it in full, check out the May 2014 Issue of AUGIworld.

Hard Surface modelling is possibly the most challenging discipline within 3D CAD  – and the most rewarding, once you’ve got the hang of it…

With a bit of surfacing theory you too can relish meeting the challenge with Autodesk Inventor!

All the surface geometry conditions

Surface modelling – what’s that?

Surface modelling is the art of building complex geometrical features – one surface at a time. Usually surface modelling is used to create flowing, organic shapes, so the junctions between surfaces are terribly important.

We describe the ‘smoothness’ of a junction, where one surface meets another, using the term ‘G’ (G stands for ‘Geometry’). We can add a suffix to our G to describe how many like characteristics each surface has. The more alike the surfaces (the more conditions that match across the pair of inputs) the more  smoothly the adjoining surfaces  flow.

G_ = nothing

Herbie the love bug cut in half

Image from Disney Wikia

I’ll always fondly remember being taken to our local library as a kid, to see the movies on a big screen (this was before cable TV and the internet,  and describing it makes me feel old!)

One personal favourite were the ‘Herbie’ films, in which a plucky VW Beetle comes to life with hilarious results. The memorable scene is when Herbie breaks in half during a race, and ends up winning  first and third place!

G Nothing

Two surfaces that don’t touch at all have no continuity. No ‘G’, nothing, nada, zip. As I try and imagine this in my mind’s eye, I can’t help but think of  the bifurcated Herbie’s classically styled lines, so similar – but sadly not connected.

Next up read all about G0 surface continuity

or read this article in full in the May 2014 Issue of AUGIworld.


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