What is the crowd's opinion of Open CASCADE?

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> Save up your money and buy a CAD programme.

Well, after the > $20K buy in cost (what I was quoted for NX), there are the recurring maintenance costs also to consider.

A CAD/CAM seat is an ongoing expense for a technology that is being commoditized, so buying in is like catching a falling knife, repeatedly. Let somebody else do it.

The opensource offerings built around the OpenCasade modeling toolkit are worth looking into.

Ref: http://www.salome-platform.org/ and http://www.freecadweb.org/ .

IGES and STEP are very different from the type of data you'd most likely see from a 3D scanner (looks like .stl, .obj, etc. from your other post).

IGES and STEP store explicit analytic boundary representations (i.e. exact surfaces) and explicit topology information (although you don't see full topology information as often in IGES, a lot of the time it's just surfaces). Just reading these formats into a workable form is quite a bit of work and requires a decent background in 3D geometry and topology. If you're trying to work with IGES or STEP then something like OpenCASCADE is very useful. It's much too heavyweight to include in something like an iPhone app, but can be used in a desktop application quite easily.

If you're working with something like STL or OBJ then it's much easier as they tend to store mesh representations (e.g. triangulated surface data) that are fairly easy to read and manipulate. Also, there are tons of libraries for reading and manipulating these file formats, less so with STEP and IGES. However, without explicit boundary representations computations like "volume" can be somewhat finicky if your input data is unverified.