# Structured faces

## Important!!!

The faces created by Flux using the algorithms of automatic construction are faces belonging to planar, cylindrical or conical surfaces.

It is possible to create faces belonging to other types of surfaces: spherical, toroidal or helical, by using the construction by extrusion.

## Building rule

To create faces belonging to spherical, toroidal or helical surfaces you should construct the faces / volumes simultaneously with the extrusion, i.e. using a building option that includes the creation of faces (Add Faces, Lines and Points / Add Volumes, Faces, Lines and Points / etc.).

## Automatic faces / structured faces

The faces created using the algorithms of automatic construction are named automatic faces.

The faces created using the construction by extrusion are named structured faces.

## Structured faces

The building of a structured face is shown in the figure below:

where:

• bottom line is the source
• upper line is the image
• side lines are connection elements

## Problems

The algorithm of automatic face construction is:

• able to identify and to create a planar, cylindrical or conical face starting from its bordering lines
• unable to identify and to create a spherical, toroidal or helical face starting from its bordering lines

## Consequence

Thus, it is necessary to respect the previously established rule to use correctly construction by extrusion.

In fact, if the default option (Add only Lines and Points) is selected:

• only points and lines are created
• the face (volume) cannot be created using the Build Faces (Build Volumes) command

This is shown in the example below.

## Example

The example that follows shows that it is necessary to respect the building rule previously established in order to construct by extrusion a volume bordered by a toroidal face.

Step Description
1

Creation of the base lines and points

Construction of the base face

2

Extrusion of the face using a rotation transformation (rotation around Z axis defined by the pivot point P and an angle of 180°)

… with the following building options: