A surface is called linear when the stiffness value is 2.

As we have learnt in a previous section, you can create a knuckle by compacting (n-1) control points on top of each other when n is the surface stiffness in that direction. So for example when a surface has transverse stiffness 3, you only have to compact 2 rows of control points. Similarly, if the surface has a longitudinal stiffness of 4, you will need to compact 3 columns of control points. In this section you will quickly learn that when you have a linear surface (stiffness = 2) you do not need to compact any control points and the surface simply follows the shape of the control point rows and columns.

Ø  Open the MyFirstDesign.msd file

Ø  Save it as MyFirstDesign_Linear.msd

Ø  Switch the transverse stiffness of the hull surface to 2 (linear):

Transverse stiffness 2 surfaces show feature lines (knuckles) at every row of control points.

Ø  Also switch the longitudinal stiffness to 2:

Completely linear surfaces have knuckle lines at every row and column.

Ø  Save the design

From this you can see that creating knuckles using linear surfaces is very easy. However, in practice this method is not used often. The reason for this is that a ship design usually consists of at least some areas with curvature which can not be achieved with linear surfaces.

Continue reading the section on When Not to Use Compacted Control Points.