Lecture Notes

Return to ARC550 home page

• Loft curves
• Bezier curves

Parametric elements

• Sweeps

4/1/02

• Curves
• The input to create curves and how they are realized by the application is quite different.
• The method of input is accomplished by defining points which describe the curve. This can be done several different ways.
• The method of display (on screen) is accomplished by creating a series of connected segments created by the specified points inputted by the user.
• The application then applies a smoothing routine (an algorithm) to generate the desired curve.
• We will be dealing with three types of curves:
• The Loft curve (this is a technical term not Form· Z specific)
• Starting and ending points are fixed, and the other control points defining the curve lie directly on the path of the curve. It is the goal of this algorithm to create a specific curve which will pass through all the specified points.
• The Bezier curve:
• Starting and Ending points are fixed, as in the loft curve. However, instead of the control points lying directly on the path of the curve as in the loft curve, the control points of the Bezier curve define the curve (by dictating where a line turns into a curve, and where that curve will bend away from it current direction). The control points do not actually lie on the path of the curve.
• There is a second type of Bezier curve where, the starting and ending points are once again fixed, however, this time the control points define a line tangential to the current control point.
• Parametric derivatives
• This can be defined simply as the ability to define an element (object) to which the user can attach certain characteristics resulting in a new form.
• Sweep
• Sweeps involve two items: an element and a path along which to sweep the element.
• First create a line (path) along which an element is to be swept along.
• Next, create the object which is to be swept.
• Select the sweep tool, click on the object, then on the path.
• A box is then brought up allowing the user to rotate the element, and further specify its alignment.