Spline Modeling Tutorial

Splines are curves mathematically fitted to flow smoothly through a set of control points. These curves are a feature common to computer aided design (CAD) programs, whose users apply splines to create objects such as custom moldings for interior design. Learning to model with splines involves understanding the concept of extrusion, which is essentially pulling a two dimensional (2-D) object into a 3-D form. Modeling with splines allows you to quickly create a wide variety of forms that polygonal (i.e. "box") modeling methods can't easily produce.

Perform a Basic Extrusion with Spline Modeling

• 1

  Open your CAD program and click its "Create" menu, followed by its "Line" tool. This is the first step of a project that will produce a 3-D letter. The project will introduce you to several concepts and procedures you can use in future spline modeling projects.

• 2

  Click anywhere in the drawing window, then drag the mouse in a motion that traces out any letter of the alphabet. Try tracing out the letter "O" for a quick and simple shape.

• 3

  Click the "Modify" menu, then click the "Extrude" command. When prompted for the element to extrude, select the letter you drew in the previous step. The application will begin the extrusion, which appears as a 3-D version of your letter. The 3-D letter's top or bottom follows your mouse cursor as you move it.

• 4

  Click the mouse once the letter has reached the thickness you like to complete the extrusion.

• 5

  Click the "Render" command in the "View" menu to produce a shaded image of the 3-D letter.

Create a Spun (Lathed) Form with Spline Modeling

• 1

  Press "Control-N" to create a new drawing document, then click the "Create" menu's "Spline" command.

• 2

  Drag your mouse to trace out any closed shape (e.g., triangle, square) in the drawing window. You'll turn this 2-D shape into a 3-D object by spinning it around an axis of revolution -- just as a rotated wooden cylinder is carved to create ornate bed posts and other decorative carpentry.

• 3

  Click the "Modify" menu's "Spin" command, then click the shape you drew in the previous step to select it.

• 4

  Click, when prompted, the screen location around which you'd like the shape to spin. A point a few inches to the left or right of the shape's center is a suitable location for your first spun model. The application will perform the spin, revolving your 2-D shape around the axis whose point you specified.

• 5

  Click the "View" menu's "Render" command to draw a realistically lit image of the spun object.