AutoCAD’s 3D modeling tools include extrusion, which turns a 2-D surface into a 3-D object.
AutoCAD is a program used by architects and others whose work requires precisely measured graphics. One of the ways such users work with AutoCAD is to simulate structures such as houses and bridges for the purpose of visualizing a proposed actual structure. The process of creating these simulations is called 3-D modeling. Among AutoCAD’s 3-D modeling tools, some are common to every computer-aided design program. They include primitives—basic shapes like spheres, cones and cylinders—and functions for transforming those shapes, such as rotation, movement and scaling.
1. Open AutoCAD and click the “Polygon” tool in the “Draw” panel. Click anywhere in the main drawing area to position the polygon’s center, then enter “4” at the prompt to indicate the number of sides.
2. Drag a slight distance to grow the polygon’s perimeter, then click to end the creation mode.
3. Change to a viewpoint that shows all three dimensions, beginning by clicking the “3-D Conceptual” item from the “Viewstyles” dropdown menu in the “View” panel.
4. Click the “View” tab, then click the “Orbit” tool. Drag slightly left and upward to change from a viewpoint that shows only one face of the 3-D object you’ll make to a viewpoint showing three faces. Right-click and select “Exit” to end orbit mode.
5. Convert the polygon into a 3-D surface using a process called “Extrusion.” Click anywhere on the polygon’s perimeter to select the polygon, then click the “Home” tab. Click the “Modeling” panel’s “Extrude” button. Notice that the polygon has expanded into 3-D space, becoming a box.
6. Drag the mouse pointer to grow or shrink the new box’s height to any size you choose. Then click the end the extrusion mode.
7. Notice the box’s parallel lines and how they make the box appear slightly distorted. The source of this distortion is the lack of perspective in the display. Perspective viewpoints make an object’s parallel lines appear to converge, the further the lines recede from you.
8. Change to a perspective view by right-clicking the cube in the upper right corner of the drawing window and selecting “Perspective.” Notice that the box’s distortion has disappeared, making the box look more three-dimensional.
9. Begin shaping the box: Click the box to select it, then right-click and select “Scale.” Click and drag on the multicolored tripod that appears. Notice that the box grows or shrinks along with your dragging action. Click to end the scaling mode.
10. Click the box again to select it, then click and drag one of its blue, squarish handles. Notice that one pair of the box’s corners follows your mouse pointer, while the remaining corners remain in place. This action illustrates a way you can begin shaping the box to make more complex objects.