Coons 101

[Anonymous]

Actually coons are quite a tricky geometric structure, normally only covered in university-level mathematics or mechanical engineering courses. They are a new invention too - first described at the end of the 60's by somebody who obviously had too little tobacco in his cigarettes.

Basically, if you create four (three-dimensional lines, thus) EDGES in space, and the corners of the lines intersect each other, you will have a description for a surface. The points on the surfaces are interpolated from the opposing edges. Think of two people holding a blanket.

The 'tricky' part is working out the formula / points for the four sides.

Note that the end points of each line have to be coincident (the same) otherwise you'll get a gdl error.

In the coil here I 'cheated' by setting two of the lines to zero (thus generating a 'pointed' end.

We'll come back to the 'spiral code' after the following example.

[Anonymous]

StuartJames wrote:
Durval; I have never tried SEO's with planar objects (never felt the need to cut up something described geometrically). Does it work?? I would guess that it probably does - but maybe with occasional errors. Risky.

I am under the impression that SEOs require solid elements to work. planar elements and surface models lack the normal vectors needed for the calculations.

[Anonymous]

Matthew wrote:
I am under the impression that SEOs require solid elements to work. planar elements and surface models lack the normal vectors needed for the calculations.

Who needs CATIA

SEO's _do_ work with planar elements. At least sometimes!

- Stuart

[Djordje]

StuartJames wrote:

Matthew wrote:
I am under the impression that SEOs require solid elements to work. planar elements and surface models lack the normal vectors needed for the calculations.

SEO's _do_ work with planar elements. At least sometimes!

Only as targets. Not as operators.

[Anonymous]

Djordje wrote:

StuartJames wrote:

Matthew wrote:
I am under the impression that SEOs require solid elements to work. planar elements and surface models lack the normal vectors needed for the calculations.

SEO's _do_ work with planar elements. At least sometimes!

Only as targets. Not as operators.

Yes, that's what i noticed. A planar element or a closed hollow shape is not a valid operator.
There is a curved slope in the library, made with ruled (hollow), and it doesn't work for SEO (as operator).

It would be great to can extrude a coons surface to get a volume.