There are three types of 3D models in the Autocad workspace; we have Wireframe models, Surface models and Solid models. This is true of any 3D computer software actually.
The first type, wireframe models, lack faces and resemble models made from wire coat-hangers in the real world. A wireframe model is typically constructed initially from 2D objects like lines, circles and arcs, etc.
Surface models are different and initially resemble solid objects. They are created from faces, but resemble objects like boxes, spheres and cones made from cardboard. If we were to dissect a surface model we would see the interior space, like an empty cardboard box.
Solid models are also made from rectangular boxes, spheres and cones, but more truly resemble objects in the real world in that they have virtual mass, and can thus be joined together, or dissected, revealing solid mass interiors.
Note at this point that models may only be created in the full version of Autocad. AutoCAD LT users are able to open and view existing 3D models, but not generate or modify the models. So, if we have the full version, we may draw an object like the wireframe wedge shown here. We use the standard Line tool, Polyline tool or Rectangle tool to create first the base rectangle, either freehand or by entering numerical values. We then use the Line tool to draw an upright vertical line from one of the corners, and click on the opposite corner, thus creating an upright triangle. We can repeat this to create the other side of the wedge, or use the Copy tool, as we would do in the 2D workspace. Finally we draw the top horizontal line to complete the shape. This is the classic wireframe shape.
To convert this wireframe into a Surface model we add flat surfaces to the edges and vertices of the wedge. But first go to the top Visual Style tab and select Conceptual or Realistic. We will not see any changes until we add our surfaces. Alternatively, we may type 3dface into the Command line. We then click on the corner-points of each surface’s face. As we do so we can rotate our view by pressing both Shift and the mouse-wheel to orbit around the box as needed, or use the Orbit tool. This completes the first face.
We can press the Enter key again to repeat the surface command for each of the wedge’s five faces. Another method is to right-click the mouse and choose Recent Input thus repeating the last command. Experiment with the different viewing modes in the Visual Style control panel. It’s important at this point to note that the wedge thus created is not a true solid object; it’s the hollow shell mentioned above, resembling more an object made of cardboard. Also please note that this method of wireframe surface modelling is not employed very often. The Solid Modelling method alluded to above is the most used these days. In the example of the wedge we would most likely use either the Wedge tool or cut a cube in half. It’s also good to note that the colours of the solid model are usually dictated by the layer’s colour. But we may add different colours to each side of the wedge via the Properties tab. Textures are also often added via the Materials browser panel.
Tom Gillan has over seven years of experience training AutoCAD 3D to corporate clients in Sydney. For more information please visit our website Design Workshop Sydney .
The Fillet tool is one way of adding realism to objects created within the 3D environment of Autocad. Fillets are smooth, curved edges on the faces of 3D objects. Related to this are chamfered edges, which are more like geometric cutaways to edges. These are measured either by distance from the true edge or as an angle, like 45 degrees.
The process of filleting an edge is simple, and has similarities to filleting the two lines which comprise a corner in the 2D interface of Autocad. To experiment with this feature first create some objects as shown in this screenshot. These were basic shapes created using the Box tool for the top bracket. The shape below used a combination of tools: the Polyline and Circle tools, then the Polar Array function, and lastly the 3D Extrude function.
To create the fillet effect we first choose the Fillet tool, or press the F key followed by Enter on your keyboard. We then have to specify the various properties of the fillet effect, the most common being the radius of the filleted edge. To do so press the R key for radius, or you may click the blue Radius text in the bottom Command line. Then hit the Enter key.
We are then asked to specify a value for the Radius in millimetres. So type in a value and press Enter again. The user then clicks on the edge (or multiple edges) we wish to fillet, and complete the operation by pressing the Enter key again.
As mentioned above, there is a related command, namely the Chamfer tool. Again we simply follow the prompts shown within the Command line to cut away the selected edges using either a distance or an angle. This command results in a harder, more geometrical edge than the softer fillet feature.
We notice the effect of adding fillets and chamfer most when we add realistic materials like glass or metal which simulate real-world effects like reflectivity and translucency. The particular qualities of these materials are best displayed in the more realistic shapes created using the fillet and chamfer commands. The human eye instantly interprets the subtle changes in tone and colour as qualities of physical objects and materials.
The effect is further enhanced by the addition of realistic lighting with shadows where the light picks up the filleted and chamfered edges, again adding a sense of realism to the objects within the scene. Autocad 3D uses a “photometric” lighting engine, which tries to simulate the bouncing of photons within a scene incorporating qualities such as tint and temperature, intensity and falloff. This is also known as Ambient Occlusion, where light and shadows are bounced around the objects. Whereas Autocad may be slightly clunky when it comes to its modelling functions (due to its accuracy and precision), it excels in its lighting and shadows.
Autocad may thus be used in conjunction with other programs, such as SketchUp, which has a much simpler modelling process. SketchUp, however, lacks the rendering power of Autocad. So the two programs used together represent a very common workflow in architecture and engineering design.
Tom Gillan of Design Workshop Sydney has trained various business consumers on AutoCAD 3D software in Sydney for over seven years now. Visit our site for more information: http://www.designworkshopsydney.com.au/autocad-3d-courses/.