Project 2b: NURBS Modeling

Goal A brief introduction to NURBS modeling.
Prerequisite Exercises

In the project we will be creating a sailboat from NURBS (Non-uniform Rational B-Spline, in case you were wondering). You can think of NURBS as a form of subdivision surface, but they tend to be less straightforward to deal with. We will not be using NURBS extensively in production and so this project will be fairly self contained. Use the Surfaces menu set for this project.

  1. In the side view, use the CV Curve Tool to create a line that resembles the one shown below (Create → CV Curve Tool). You will probably find grid snapping useful (hold x). Hit Enter to complete the curve. This curve will form the basis of our hull.x
  2. With the curve selected, go to Edit → Duplicate Special (Options). Change the third value of "Rotate" (The Z value) to 30 and set "Number of copies" to 3. Click Duplicate Special to finish the action.
  3. Select the curves from highest to lowest and then do Loft (Surfaces → Loft). After you have done this, we no longer will need the curves and so delete them.
  4. With the lofted surface selected, we will do another Duplicate Special (Options). In the Options dialog, go to Edit → Reset Settings and then set the first "Scale" value (The X value) to -1. Duplicate to create the other half of the hull.
  5. Change both pieces of the hull to Isoparm mode by Right clicking each piece in turn and selecting "Isoparm" from the radial menu. Isoparms are the blue lines you will see in this mode. Once both pieces are selected, group select the center isoparms and do Attach Surfaces (Edit NURBS → Attach Surfaces). This will create a new NURBS surface that traverses the entire hull. Delete the old pieces before moving on.
  6. In the front view, change to Control Vertex (CV) Mode using the radial menu. Scale in the CVs to create a sharper keel.
  7. In the side view, switch to Isoparm mode. Insert a few new isoparms by clicking on an existing isoparm and then dragging it to the desired location. Use Insert Isoparms to finalize the new isoparms (Edit NURBS → Insert Isoparms).
  8. Move the CVs to create a keel.
  9. Create a rudder using a NURBS Cube (Create → NURBS Primitives → Cube). Adjust the CVs to create a more rudder-like shape. Note that a "NURBS Cube" is just 6 NURBS planes, so be careful that you have selected all the correct components when moving CVs.
  10. Shift select the two topmost isoparms and Loft them to create the deck.
  11. In the side view, create a closed curve using the CV Curve Tool. To create a sharp turn in the curve, snap three CVs to the same location. Make sure that the first and last CV are snapped to the same location, otherwise the next step won't work. Create two windows using NURBS Circles (Create → NURBS Primitives → Circle).
  12. Selecting the outer curve first, then the windows, create the side of the cabin using Surfaces → Planar. Delete the curves that were used to construct the cabin, select all of the CVs that define the side of the cabin, then move and rotate them into place (don't use object mode in this case as it will change the pivot point). Create the other side of the cabin by using a Duplicate Special with an X Scale of -1.
  13. Convert each side of the cabin to Trim Edge mode by Right clicking each side and selecting Trim Edge. Shift select the outermost edge of each cabin side and then Loft to create the cabin roof.
  14. To give the windows some depth, select the Trim Edge surrounding a window and Surfaces → Extrude (Options). Set the "Style" to Distance, the "Direction" to Specify, and the "Direction Vector" to X axis. Choose a small "Extrude length", which will have to be negative depending on which side of the boat you are on. Once you have created the inset, select the inner isoparm of the inset and do Surfaces → Planar to fill the hole. Do this for all four windows.
  15. Use a cylinder to create a tapered mast (Create → NURBS Primitives → Cylinder). Create the boom by duplicating and manipulating the mast.
  16. In the side view, create three CV curves using the CV Curve Tool. Each curve should define one side of the sail. Do this for the front and back sails.
  17. Select the three curves of a sail and do Surfaces → Boundary to create the sail surface. Do this for both sails. Delete the curves when you are done. Adjust the CVs in the sails to give them a more fabric-like appearance.
  18. That finishes the majority of the work on the sailboat. You can delete all of the History at once by going to Edit → Delete All by Type → History. Go through your Outliner and rename things appropriately. Make sure all the components are grouped under a single group named something reasonable like "sailboat".
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