Chapter 2 Creating Primitives and Composites 27 Copyright Goodheart-Willcox Co., Inc. Cylinder A cylinder has a circular or elliptical base and edges that extend perpendicular to the base. See Figure 2-7. When the command is initiated, you are prompted for the center point of the cylinder base, or to enter an option. If you pick the center, you must then set the radius of the base. To specify a diameter, enter the Diameter option after specifying the center. The 3P, 2P, and Ttr options are used to defi ne a circular base using three points on the circle, two points on the circle, or two points of tangency on the circle and a radius. The Elliptical option is used to create an elliptical base. If the Elliptical option is entered, you are prompted to pick both endpoints of one axis and then one endpoint of the other axis of an ellipse defi ning the base. If the Center option is entered, you are asked to select the center of the ellipse and then pick an endpoint on each of the axes. After the base is defi ned, you are asked to specify a height or to enter the 2Point or Axis endpoint option. The 2Point option is used to set the height by picking two points on screen. The distance between the points is the height. The Axis endpoint option allows you to orient the cylinder at any angle, regardless of the current UCS, just as with a cone. The Axis endpoint option is useful for placing a cylinder inside of another object to create a hole. The cylinder can then be subtracted from the other object to create a hole. Refer to Figure 2-8. If the axis endpoint does not have the same X and Y coordinates as the center of the base, the cylinder is tilted from the XY plane. CYLINDER Ribbon Home Modeling Solid Primitive Cylinder Type CYLINDER CYL Figure 2-5. A—A circular cone. B—A frustum cone. C—An elliptical cone. A B C A B Figure 2-6. A—Cones can be positioned relative to other objects using the Axis endpoint option. B—The cone is subtracted from the box.