1- Disclaimer

trimaran Kenau. The trimaran project proved that Rhino is a professional tool to turn an idea into reality. More and more, Petersen became convinced that Rhino is the perfect tool to model any vessel hull whether it is a ship, boat or yacht. The next step was to bring his developed knowledge and experience to a training. This way, anyone can profit from Rhino being a hull design and fairing tool. As Petersen offers Rhino training since 2005, he also has to experience how to transfer knowledge in a comprehensible way.

Training Videos of the exercises

Naval architect Bas Goris created the training videos of the exercises 2-23. Petersen created the training videos 24-35. Goris will also be one of the people who is assigned to give online training support for the 'Hull Design and Fairing' training modules. Goris developed the first ideas of the Rapid Hull Modeling Methodology in 2002. Then he shared this method with RhinoCentre which made it possible to continue its development.
  • Exercise 2-23 are made in Rhino 5.
  • Exercise 24-35 are already made in Rhino 6 as it will be released in early 2018. As you will see, the look and feel of Rhino 6 is similar to Rhino 5. What will catch your eye mostly is that Rhino 6 shows the control points of curves when you select them.
  • The videos of Exercise 24-35 are made at a resolution of 1920x1080 pixels.
  • The videos of Exercise 2-23 are made at a lower resolution.
  • The videos often zoom in and out to focus on the action of typing a command, turning on/off a layer etc. This is also done for those who watch these videos on a smaller screen like a tablet for example.
  • The videos also often contain annotations that display the current action. For example arrows point out to look at another location than the position of the mouse pointer at that specific moment. Also often the use of specific keys on the keyboard are indicated. This might probably seem a bit stupid or unnecessary but this is also done for people who are deaf, have other hearing problems or find it difficult to understand the English pronunciation.
  • We would like to hear your comments on the videos to be able to improve them.

About RhinoCentre

Since 2003 RhinoCentre shares and increases Rhino knowledge in offering training, consultancy and other services to the marine industry worldwide. The best example is the joined development of the Rapid Hull Modeling Methodology with people of several companies and organizations. On the other hand is RhinoCentre in close contact with McNeel & Associates, the developers of Rhino as well as plugin developers to make Rhino even better. RhinoCentre maintains with most of their customers a long lasting relationships based on trust and equality. Please contact us if you need any help regarding Rhino related issues.

About the value of this training

We have invested more than a decade of experience in this training. To develop a training module like this one takes us at least three months. You and your company paid for this in time and money. Please keep this in mind in case you’re considering giving this training (or the associated training files) away, or even worse, publishing it on internet. There is no way we can prevent this with protections. Actually we don’t even want to try. We simply trust you on this.
  • Training based on Rhino version 5.0
  • Training Manual September 2017
  • Copyright RhinoCentre 2012-2017,  All Rights Reserved
  • This manual is part of the training curriculum offered by RhinoCentre
  • Please don't share this training module with other people
  • It is forbidden to make digital or hard copies of this training module or a part of it
Note: Rhinoceros is a registered trademark and Rhino is a trademark of Robert McNeel& Associates. All other brand or product names are registered trademarks or trademarks of their respective holders.  

4- Before you start

Exercise 1: Before you start
  • Make sure 'Grid Snap' is turned off and 'Ortho', 'Osnap' and 'Planar' is turned on in the status bar (Fig.2)
[caption id="attachment_8667" align="alignnone" width="700"] Fig.2: Osnap toolbar & Status bar[/caption] [caption id="attachment_8662" align="alignright" width="412"] Fig.3: Layer manager panel[/caption]
  • Make sure that the Osnap toolbar is visible (Fig.2). If it’s not, go to 'Tools' > 'Object Snap' > and check 'Persistent Osnap Dialog'
  • In the Osnap toolbar (Fig.2), turn on the following object snaps: 'End', 'Near', 'Point', 'Mid', 'Cen', 'Int'
  • Make sure the Layer manager panel is visible (Fig.3). If it’s not, then run the _Layer command
  • Download now the necessary training files: M1R1 - Training Files - Online
  • Make sure to store the files in a secure place on your hard drive.
  • Now copy the training files folder to the desktop. This makes it most easy to access the necessary files during the training.
  • At last, create a new folder on your desktop and name it "WIP" (Work In Progress). In this folder you can save your training files thus keeping the original files clean.

Rhino viewport orientation

At this point one word about Rhino viewport orientation in Rhino. In naval architecture, the hull center line orientation is along the X-axis which is unfortunately inconsistent with the Rhino viewport setup because:
  • The side view of the hull is called 'Front' in Rhino.
  • The front view is called 'Right' in Rhino.
It is possible to rename views in Rhino, however to avoid confusion with other Rhino users and when working with Rhino files from other people, this training uses Rhino default viewport names.    

5- Setup a Custom Display

7- Design a merchant ship hull from scratch

8- Considerations and understanding

9-Fairing techniques

[caption id="attachment_9253" align="alignright" width="320"] Fig. 53: Move control point Ref-6 until it intersects the assist line[/caption]


One very important factor in modeling Class-A surfaces is control on continuity from one surface to another surface. Surfaces should at least touch each other at the full edge in order to create ‘watertight’ objects. But then, what kind of transition is desired? Fluent? But what is fluent? Most important is to understand that the user of Rhino makes proper decisions and is in control of Rhino to achieve the desired result. The result should often reflect the reality of shipbuilding. This means that when a part of a ship is manufactured by welding a quarter of a pipe to straight sheets of metal, the smoothness will be less fluent compared to a part that is modeled and manufactured with G2 continuity. One is not better than the other because both solutions serve another purpose. This will be explained in the following exercise: Exercise 28: Continuity [video width="1920" height="1080" mp4="https://www.rhinocentre.nl/wp-content/uploads/2017/11/M1R1-Ex.-28-Ger-R6.mp4"][/video]  
Exercise 28: Continuity
  • Turn on layer "Exercise > Continuity". Notice in the "Front" viewport a stem shape which is a quarter of an ellipse
  • Click at the curve to find out that it contains three individual segments. One straight keel line, a straight bulwark line and a stem curve
  • Turn on the control points of the three objects and notice that the objects appear to be ‘clean’. The stem profile is a 2 degree curve with 3 control points
  • Turn on the curvature graph for all three curves and set the Display Scale to the value 150. Notice that the straight lines have zero curvature and the stem-curve a curvature that varies
  • Turn off the curvature graph and control points display.
Let’s check some other solutions for the stem shape.
[caption id="attachment_9255" align="alignright" width="364"] Fig. 54: BlendCrv between the two straight lines[/caption]
  • Run _BlendCrv and select the two straight lines at Ref-1 and Ref-2 (Fig. 54)
  • Select “Tangency Continuity” for connection 1 and 2 and notice that the black curve is near the original red stem curve
  • Make sure the option “Show curvature” is turned on. Notice Tangent continuity contains four control points instead of three at the degree 2 stem curve. Apparently the Tangent continuity needs two extra control points besides the two end points
      [caption id="attachment_9254" align="alignright" width="320"] Fig. 55: Click and drag the BlendCrv handles to adjust the blend[/caption]
  • Press [Shift] and click one of the BlendCrv handles (Fig. 55) (once the handle is active you can release Shift). Drag the point until the shape of the curve looks more similar to the red arc. Click again to fix that new position. Move the other handle (without Shift) until the curve matches even better. Play with this until you are satisfied. Notice that when moving the handles, the curvature graph changes accordingly. When the curve matches the original stem curve, near Ref-2 the curvature graph increases again. Although the shape matches the original stem curve, still the curvature graph is discontinuous at the start- and end point of the stem curve. Notice the leap.
The [Shift] option of the BlendCrv command creates symmetry between the two handles. If you move one side the opposite handle moves as well.
  • Switch to “Position Continuity” for both connections. This results in a straight line that closes the gap between the two lines. The curve contains only a start- and end point now. Position Continuity is also called G0 and the curvature is zero. At least the bow is closed now… 😊
  • Now switch back again to “Tangency” for both connections and notice that the curve contains one extra control point after the start point and one extra control point before the end point. Tangent Continuity is also called G1 (a Mnemonic is: one extra control point is added to the start- and one to the endpoint)
  • Try out “Curvature Continuity” for both connections and notice that the curve now contains two extra control points after the start point and two extra control points before the end point. Curvature Continuity is also called G2 (2 extra control points at each end). Notice that near Ref-2, the curvature graph shows also a shape that starts concave and flips to convex. Is this acceptable?
Notice that the curvature graph declines to zero at both ends of the stem curve. As the straight lines also have zero curvature, “Curvature continuity” is more fluent than Tangent continuity but the curvature graph still shows a kink at the connections. This is not wrong, but can be the character of curvature continuity.
  • Now drag the second control point from Ref-1 to the left to make the shape overall convex
  • Try again to match the original red arc by moving the control points with or without pressing [Shift].
You probably find out after a while that this Curvature continuity will never match the Arc perfect due to the nature of both objects. This isn’t necessarily a problem but something to take into account when making decisions.
[caption id="attachment_10505" align="alignright" width="240"] Fig. 56: G3 – still a kink in the curvature graph[/caption]
  • Next to try out is G3 continuity on connection 1 and 2. It will be no surprise that in this case three extra control points are added after the start point and three control points are added before the end point. Notice also that the curvature graph is now also smooth at the two connections which mean that G3 continuity is more fluent than Curvature continuity (Fig. 56)
            [caption id="attachment_10504" align="alignright" width="240"] Fig. 57: G4 – now the curvature graph is smooth[/caption]  
  • At last there’s also a G4 option which leads to the insertion of even more control points resulting in the smoothest solution. The question is however if you need such a smooth connection (Fig. 57)
  • As you are still in preview of the _BlendCrv command, it is time to finish it. Create the desired shape of the stem curve and take the curvature graph into account. Then press [Enter]
  • Switch back to four viewport display
  • Turn off layer “Continuity” and turn on layer “Ship Hull Design” again.
So far about continuity. With this knowledge you are now able to master every connection from now on and make your decisions from a practical point of view.
G0 = Position Continuity G1 = Tangent Continuity G2 = Curvature Continuity G3 G4

Reference curves

In many cases some curves are used to define the shape of the ship hull in one or more directions. This can be for example a deck contour, a main frame curve or a keel line. These curves can be drawn in Rhino or imported from AutoCAD for example. Exercise 29: Using a Reference Curve [video width="1920" height="1080" mp4="https://www.rhinocentre.nl/wp-content/uploads/2017/11/M1R1-Ex.-29-Ger-R6.mp4"][/video]  
Exercise 29: Using a Reference Curve [caption id="attachment_9258" align="alignright" width="320"] Fig. 58: Using a Reference curve[/caption]
  • Turn on layer "Exercise > Ref. Curve Modeling" which shows a red curve of a deck contour in the bow area. In the "Top" viewport this curve shows a more elegant bow shape compared to the existing blunt bow
  • Turn on the control points of the loft curves 3, 4 and 5 (Fig. 58)
  • Move the uppermost control points of the loft curves in such a way that the bow surface meets the reference curve. Use Drag, Move, Nudge or Gumball.
  • Unlock the layer "Ship Hull Design > Loft Surface"
  • Select the loft surface and run _CurvatureGraph.
    [caption id="attachment_9259" align="alignright" width="320"] Fig. 59: Curvature graph color[/caption]
  • The curvature graph of surfaces is often confusing because it’s displayed for all isocurves at once. Nevertheless, we’ll still use it to examine the fairness of the deckline in the "Top" viewport by changing the color of the 'U' surface direction in the curvature graph dialog (Fig. 59) which makes it easier to maintain an overview
  • Relock the layer "Ship Hull Design > Loft Surface" and turn off layer "Exercise > Ref. Curve Modeling" when done.

Reference objects

Besides curves other objects can be used as a reference too, for example volumes for a cargo hold or a propulsion system setup. It is important to take a margin into account for the structure for example. Another reference object might be a cylinder for propeller clearance. When these objects are modeled in 3D they can be used for reference. Exercise 30: Using a Reference Object [video width="1920" height="1080" mp4="https://www.rhinocentre.nl/wp-content/uploads/2017/11/M1R1-Ex.-30-Ger-R6.mp4"][/video]  
Exercise 30: Using a Reference Object [caption id="attachment_9260" align="alignright" width="320"] Fig. 60: Using a Reference Object[/caption]
  • Turn on the layer "Exercise > Ref. Objects" which shows one box shaped cargo hold volume and a propeller clearance cylinder. Although it is evident that the box cuts the hull surface (Fig. 60) this is a good example to show the functionality of making an intersection curve
  • Unlock layer "Ship Hull Design > Loft Surface"
  • Run the _Intersect command and select the hull surface and box. Rhino reports: "Found 1 intersection." and an intersection curve displays exactly the shape of the intersection
  • Delete the intersection curve
  • Move loft curves 5 and 6 forward 1500mm.
Is the cargo hold enclosed now? To make sure that the cargo hold is fully enclosed an intersection curve is made from the loft surface and cargo hold box.
  • Run _Intersect again
  • On the "Select objects to intersect:" prompt, select the loft surface and cargo hold and press [Enter]
  • Rhino reports: "Found 0 intersections".
  • Use the techniques you've learned up to now to lower the bottom surface near the propeller until it nearly touches the propeller clearance cylinder.
  • Lock layer "Ship Hull Design > Loft Surface".

Adding and Deleting Control Points

Designing ship hulls with the Rapid Hull Modeling Methodology starts with creating the loft curves. Their shape is defined by a number of control points. Suppose we need more control and more control points are desired at a later time? Or it turns out that too many control points where used to model simple shaped loft curves? In Rhino it is easy to add or delete control points, so don't worry much when defining loft curves at the start of a new project. The following exercise creates more volume in the aft ship region: Exercise 31: Adding/deleting control points [video width="1920" height="1080" mp4="https://www.rhinocentre.nl/wp-content/uploads/2017/11/M1R1-Ex.-31-Ger-R6.mp4"][/video]  
Exercise 31: Adding/deleting control points [caption id="attachment_9261" align="alignright" width="320"] Fig. 61: Insert Control Point[/caption]
  • Turn on the control points of the two stern loft curves
  • Turn on layer "Exercise > Ref. Add control points" This shows two + symbols along the loft curves
  • Run the _InsertControlPoint command
  • On the "Select curve or surface for control point insertion:" prompt, pick one of the two stern loft curves
  • On the "Point on curve to add control point:" prompt, pick a point near the + symbol (Fig. 61) and press [Enter]
  • Repeat the last 3 steps with the other curve.
  • Select the control points at center line of both stern curves
  • Move them down with Nudge until the hull surface nearly cuts the propeller cylinder.
  • Turn off the layers "Exercise > Ref. Objects" and "Exercise > Ref. Add control points".

Display Mesh

Surfaces in Rhino are described with NURBS mathematics. However graphics cards can only show the NURBS surfaces in wireframe display. To show the surfaces in shaded or rendered display Rhino generates automatically a so called 'render mesh' for each surface with a default smoothness. This explains that sometimes the edge curves of a surface show smooth and accurate but the surface itself shows rough and ugly. Especially during fairing with the Glossy for Fairing display it is important to have a smooth render mesh. Exercise 32: Display Mesh [video width="1920" height="1080" mp4="https://www.rhinocentre.nl/wp-content/uploads/2017/11/M1R1-Ex.-32-Ger-R6.mp4"][/video]  
Exercise 32: Display Mesh [caption id="attachment_9262" align="alignnone" width="474"] Fig. 62: Custom Mesh & Simple Mesh Options dialog[/caption]
  • Switch the Perspective viewport display to 'Glossy for Fairing'
  • Select the loft surface
  • Zoom in at the bow area
  • In the Object Properties menu select the checkbox for a Custom Mesh (Fig. 62).
  • Click Adjust. The 'Polygon Mesh Options' dialog pops up (Fig. 62)
  • Click at Preview and look at the mesh faces on the surface
  • Move the slider to 'Fewer polygons' and click at 'Preview' again. Notice the large mesh faces along the surface and the straight lines at deck level. This doesn't look smooth
  • Move the slider to 'More Polygons' and click 'Preview' again. This looks much better. However the bulbous bow is still very rough
[caption id="attachment_9263" align="alignnone" width="512"] Fig. 63: Detailed Mesh Options dialog[/caption]
  • Click 'Detailed Controls' in the Simple Mesh Options dialog and set the values according to Fig. 63.
  • Click Preview again. The mesh faces distribution is much more refined now.
  • Press OK to accept these settings and examine the display quality of the surface.
In the detailed controls:
  • Toggle 'Refine mesh'.
  • Set maximum aspect ratio to '1' to create more or less square mesh panels and avoid thin and long mesh panels.
  • Now play with 'Maximum distance, edge to surface' setting. First set it to a bit higher value (for example 10 mm) and do a preview. Then, step by step, make this setting smaller and preview.
It is important to understand that the more refined the Display Mesh is, the larger the file size will become as each Mesh face has to be described. Furthermore editing the shape of the hull is slower with a detailed render mesh as it has to be recomputed over and over again. On the other hand a sufficient level of detail of a render mesh is necessary to be able to examine the surface smoothness. Finding the proper balance here is very important.

10- Intersections

11- Investigate hull type examples

Fig. 4.1 Environment map image
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