LESSON 3-1

INTRODUCTION - WHY 3-D? You may have already found out why CAD has many advantages over manual drafting. One big advantage is that once you've drawn something, you shouldn't have to draw it again. If you manually drew a house plan, you would have to draw a front elevation, side elevations, and possibly a perspective view. With one 3-D CAD model, you can generate views from any angle either inside or outside the house. Afterwards, if your client needs something changed, you can then make the changes once. If you're drawing mechanical parts, you can generate virtual prototypes or even create rapid prototypes. In this manner Boeing was able to design and prototype the 777 jetliner. This level of engineering would be impossible without CAD. You'll be learning the 3-D concepts in the following order: o Isometric Drawings (not true 3D) o Wire-frame o Surfaces / Regions o Solid Objects You will have a chance to draw the same object different ways to see the differences between the various methods. Before entering the exciting world of 3-D, you'll have to learn some more CAD terminology 3-D CAD TERMINOLOGY 2-D A concept of displaying real-world objects on a flat surface showing only height and width. This system uses only the X and Y axes. 3-D A way of displaying real-world object in a more natural way by adding depth to the height and width. This system uses the X Y and Z axes. Boolean operations Commands that allow you to add, subtract or intersect solid objects in AutoCAD. Complex surface Generally a curved surface. Examples: car fender, landscape contour. Elevation The difference between an object being at zero on the Z-axis and the height that it is above zero. Extrude The extrude command raises the shape of a 2D outline into a 3D solid. For example, a circle would be extruded into a cylinder. Face The simplest true 3-D surface. Facet A three or four sided polygon that represents a piece (or section) of a 3-D surface. Hidden line removal A way of hiding lines that would not be visible if you were viewing the actual object you have drawn in AutoCAD. (Command: HIDE) Isometric Drawing A simple way of achieving a '3-D' appearance using 2-D drawing methods. Plan View Also known as the top view, a plan view looks directly down the WCS Z-axis to the X-Y axis. Primitive A basic solid building block. Examples would be boxes, cones, cylinders. Region A 2-D area consisting of lines, arcs, etc. Rendering A complex way of adding photo-realistic qualities to a 3-D model you have created. Shading A quick way of adding color to a 3-D object you have drawn. (Command: SHADE) Solid Model A 3-D model creating using solid 'building blocks'. This is the most accurate way of representing real-world objects in CAD. Surface Model A 3-D model defined by surfaces. The surface consists of polygons. (See facets.) Thickness A property of lines and other objects that gives them a 3-D like appearance. UCS The user co-ordinate system. This is defined by the person drawing to have easier access to portions of a 3-D model. View A particular view of the object you have created. Viewport A window into your drawing showing a particular view. You can have several viewports on your screen. Different from the viewports used in plotting. Wire-frame Model A 3-D shape that is defined by lines and curves. A skeletal representation. Hidden line removal is not possible with this model. Z-Axis The third axis that defines the depth. As computers and software get more sophisticated, working in 3D becomes more popular. You have more power in desktop machine today, than was dreamed of when CAD first appeared. Be prepared that you will likely need to learn 3D at some point in your career. Once you are comfortable working in 3D, you'll find that you will rarely want to draw in 2D again. Autodesk (the makers of AutoCAD) make other products designed specifically for certain disciplines - Architectural Desktop, Map, 3D Studio Max and more. Depending upon your budget and needs, you may need to look into programs like these. The concepts taught in these lessons will aid you when you work in any 3D program.