After you have set up a surface with approximately the right size, stiffness and number of control points and have also defined a grid, zero point and Frame of Reference, you can start shaping the design. Again you can do this in any random order you like, but from the author’s experience there is a particular sequence that works very well and it is recommended to follow this for now. The most efficient way to manipulate the shape of this surface is by working your way through the three types of control points from top to bottom:

§    Corner control points

§    Edge control points

§    Internal control points*

* If the difference between corner, edge and internal control points is not clear, read Chapter 2 of the Maxsurf manual.

Following this order will prevent you from making unnecessary adjustments to internal control points and reduce the number of iterations you will have to do to achieve the desired hullshape.

Just to recap on the previous section in this training where we explored the User Interface, here are some tips and tricks that are worthwhile remembering when manipulating the shape of a design:

1.      An adjustment to the shape in a 2D window influences the 3D shape and thus in the other 2D windows and Perspective window.

2.      Alternate between different view windows regularly when modelling

3.      When starting a new model, make big changes first whilst alternating between view windows and then slowly refine towards to required shape. Don’t try to do it all at once in just one view window.

4.      Arranging your view windows can improve your productivity. For example: you can show all four view windows at the same time and see how a change made in one window effect the hullshape in the other windows.

 Watch a short video that shows you how to set the 4 corner control points positions numerically, and then manipulate the edges in the different view windows. This video also shows how to use the Control Box in Body Plan view is used to activate different columns of control points. [Web | Disk]

Positioning the Corner Control Points

Each surface consists of four corner control points. The corner control points can be recognised by their colour or by following the edges to the surface:

Note:

The location of the corner control point is the exact location of the surface.

For a design that consists of only one surface, the location of the four corner control points are more or less determined by the design’s Length, Beam and Depth parameters as in the following table.

* Corner control point number 4 is always very difficult to position.

Ø  Enter the following coordinates for the four corner control points by double clicking on each of them.

Perspective is probably the best window to select the corner control points.

When you look at your surface now in the different view windows, it looks pretty messy. Don’t worry about this at the moment and more importantly: don’t try to fix it by starting to randomly drag control points around. Trust on the fact that the order of modelling: Corner control points è Edge control points è Internal control points will sort it all out for you. Let’s continue modelling by manipulating the edge shapes.

Ø  Save your design MyFirstDesign_CornersEdges.msd

Manipulate the Edge Shape

Ø  First read Chapter 3, section “Moving Control Points” of the Maxsurf manual

To make sure you do not get confused by the large number of control points,

Ø  Hide the Net , switch buttocks off

This hides the internal control points, so that you can concentrate on the shape of the edges. You can now begin to manipulate the default surface into the required design shape. This is simply a case of dragging the control points to their required positions. In general, it is best to define the edges in the following order:

Ø  Switch to Profile View

When manipulating the edge shape in Profile view, move the control points primarily up and down. Out of edge 1, 2 and 3 in the image below you can start with any edge you like. Edge 4 (transom) will be adjusted in Body Plan view.

Ø  Drag the control points so that it looks something like this:

Tip:

Try not spending too much time on achieving the exact control point positions at this stage. Modelling is an iterative process where you increase the accuracy of the control points’ positions as the design progresses.

You can see that the surface edge contour does not go through the position of the edge control point. This means that typing in the numerical values of the edges is not very useful. Remember to imagine the surface being connected to the control points via little springs or rubber bands. Read the “The Spline and Spring Analogy” in the Maxsurf Manual if this is unclear to you.

Ø  Switch to Plan View, switch waterlines off, Half off, Hide Net.

In Plan view you shape the deck edge. You will see that your design currently looks something like this:

First thing we need to do now is use a multiple selection on edge # 2 (the bow) like this:

With these edge control points selected,

Ø  Controls | Control Properties

Ø  Specify Offset = 0 and OK to move all control points to the centreline and close the bow

In the control properties dialog all properties that the selected control points have in common are displayed. In this case the selected control points do not share the same row number, longitudinal position, offset or height, but do all have a weight factor of 1.000 and are all in column 4 on the Hull surface.

Ø  Switch to Perspective view to check your work so far:

Perspective view with sections displayed

Smooth Shading rendering in Perspective view

Note:

When you are shaping your edges, do not:
     - touch your corner control points anymore
     - display your internal control points by showing the Net.

Ø  Switch to Body Plan View, Hide Net, Sections off, Half on.

What you are looking at now is called the active column. When the Net is hidden in Body Plan view, the only control points you’ll see in Body Plan view are the “active column” control points. Active column control points are the control points on the column that is associated with the control point that you selected last.

Let’s have a look how this works:

Ø  In Perspective view Select the following control point in the bow column:

Ø  Switch back to Body Plan:

1 = Section, 2 = Transom edge, 3 = Bow column of control points, 4 = Deck edge.

Ø  In Perspective window, select this control point:

In Body Plan you’ll see this column is now the active column and the deck edge control point is selected:

The column that is displayed in Body Plan view when the Net is Hidden is called the “active column”. This is the column with the last selected control point in it.

The active column is indicated in the Body Plan window control box:

The control box shows that there are 5 columns on this surface
of which the 3^rd is the active column.

You can also switch active columns by clicking on the column indicators. When you do that, Maxsurf also displays the Section that is closest to the active column. This enables you to model on one column and its nearest section at a time.

Ø  Click on Column indicator #1 in the Control box in body plan view.

What you are looking at now is the Transom edge on the left and the transom edge control points on the right.

The Transom edge Control points

Ø  Drag the control points on the aft most edge so that it looks like this (do not move the corner control points):

Let’s take a moment to have a closer look at the transom shape:

Ø  Switch Half Off and zoom in on the centreline-transom point:

Notice how the transom edge is tangential to the control point net from the corner control point to the next adjacent edge control point. This is always the case for all edges and is very important to remember!

This means that the following three scenarios are possible for the transom edge:

Let’s shape the transom so that it is smooth:

Ø  Double click on the corner control point:

The height of the corner control point = 0.5 m

Ø  Now double click on the adjacent edge control point of the transom and set the height to 0.5 m as well:

You have now completed positioning the corner control points and modelling the edge shapes.

Ø  Save your design as MyFirstDesign_CornersEdges.msd