3D Drawing with AutoCAD - Section 8

CHAPTER 33: THE SPACE MODELED IN 3D

As we explained in section 2.11, Autocad has a workspace called "3D Modeling" that puts at the user's hands a set of tools on the ribbon for drawing and/or design work in three dimensions. As we saw right there, to select that workspace, simply select it from the drop-down list on the quick access bar, with which Autocad transforms the interface to show the related commands. In addition, as we also studied in section 4.2, we can start a drawing from a template file, which can contain by default, among other elements, views that also serve the purposes of the 3D drawing. In this case, we have a template called Acadiso3d.dwt (which uses units in the metric system), which, combined with the “3D Modeling” workspace, will give us the interface that we will use in this and the following chapters. .

With the new perspective that gives us this interface, not only by the view in the workspace, but also by the new commands in the ribbon, we must review issues that we already dealt with in drawing 2D, but adding the factor of Tridimensionality we have now. For example, we must study the tools to navigate in this space, which allow us to manipulate new SCP (Personal Coordinate Systems), new types of objects, specific tools for their modification, and so on.
Either way, the reader should try to get used to using the workspace appropriate to each case (drawing 2D or 3D) and even to exchange between them according to their needs.

CHAPTER 34: SCP IN 3D

When technical drawing was an activity that had to be developed exclusively with drawing instruments, such as squares, bars and rulers on large sheets of paper, the drawing of the different views of an object, which in real life is three-dimensional, was a work Not only tedious, but also very prone to error.
If a mechanical part had to be designed, if it were simple, you had to draw at least one front view, one side view and one top view. In some cases an isometric view had to be added. To those who have had to draw this way, they will remember that they began with one of the views (the front, commonly) and it was created extension lines to generate the new view on sheets of paper divided into two or three parts, according to the number Of views to create. In Autocad, however, we can draw an 3D model that will behave as such with all its elements. That is, it will not be necessary to draw a front view, then a side and a top view of an object, but the object itself, as it would exist in reality and then simply arrange it as necessary for each view. So, once the model is created, no matter where we have to see it, you will not lose any detail.

In this sense, the essence of the three-dimensional drawing is to understand that the determination of the position of any point is given by the values ​​of its three coordinates: X, Y and Z, and not only two. By mastering the handling of all three coordinates, the creation of any object in 3D, with the precision of Autocad, is simplified. So the issue goes no further than adding the Z axis, and everything we've seen so far about the coordinate system and the Autocad drawing and editing tools is still valid. That is, we can determine the Cartesian coordinates of any point in an absolute or relative way, as studied in chapter 3. Also, these coordinates can be captured directly on the screen using object references or using point filters, so if you have forgotten how to use all these tools, it is a good time to review them before continuing, in particular the 3 chapters, 9, 10, 11, 13 and 14. Walk you, take a look, we will not go, I assure you, here I wait.
Already? Okay, let's move on. Where there is difference, it is on the subject of polar coordinates, which in an 3D environment are equivalent to what are called Cylindrical Coordinates.
As you will recall, the absolute polar coordinates allow you to determine any point in the Cartesian plane 2D with a value of distance to the origin and the angle with respect to the X axis, as we illustrate with the video 3.3, which I will allow to be prescribed it of new.

The cylindrical coordinates work exactly the same, only adding a value on the Z axis. That is, any point in 3D is determined with the value of the distance to the origin, the angle with respect to the X axis and the elevation value perpendicular to that Point, that is, a value on the Z axis.
Let's assume the same coordinates of the previous example: 2 <315 °, so that it becomes a cylindrical coordinate we give the elevation value perpendicular to the XY plane, for example, 2 <315 °, 5. To see it more clearly, we can draw a straight line between both points.

Same as polar coordinates, it is also possible to indicate a relative cylindrical coordinate, putting an at sign for the distance, the angle and Z. Remember that the last point captured is the reference to set the next point.
There is still another type of spherical coordinates, which in synthesis, repeat the polar coordinate method to determine the elevation of Z, that is, the last point, using the XZ plane. But its use is, rather, infrequent.
What should be clear in all methods is that the coordinates should now include the Z axis to be in 3D environment.
Another essential to drawing in 3D is understanding that in 2D, the X-axis runs horizontally across the screen, with its positive values ​​to the right, while the Y-axis is vertical, with its positive values ​​pointing up from a point of view. origin which is usually in the lower left corner. The Z axis is an imaginary line that runs perpendicular to the screen and whose positive values ​​are from the surface of the monitor to your face. As we explained in the previous chapter, we can start our work using a “3D Modeling” workspace, with a template that lays out the screen in a default isometric view. However, even so, whether it is this view or a 2D view, there will be, in both cases, many details of the model to be built that will be outside the user's view, since they will either be available only from a view. orthogonal different from the default (top), or because an isometric view is needed whose starting point is the opposite end to the one on the screen. Therefore, it is essential to start with two essential topics to successfully tackle the study of 3D drawing tools: how to change the view of the object to make it easier to draw (a topic that we started in chapter 14) and that, in short, we could define such as methods for navigating in 3D space and how to create Personal Coordinate Systems (PCS) like the ones we studied in chapter 15, but now considering the use of the Z axis.
Let us see then both subjects.