Autodesk AutoCAD 2013 Practical 3D Drafting and Design: Take your AuotoCAD design skills to the next dimension by creating powerful 3D models.

The location of all entities in AutoCAD is related to a coordinate system. Any coordinate system is characterized by an origin and positive directions for the X and Y axes. The Z axis is obtained directly from the X and Y axes by the right-hand rule: if we rotate the right hand from the X axis to the Y axis, the thumb indicates the positive Z direction.

Picture that when prompting for a point; besides specifying it in the drawing area with a pointing device such as a mouse, we can enter coordinates using the keyboard.

The format for the absolute Cartesian coordinates related to the origin is defined by the values of the three orthogonal coordinates, namely, X, Y, and Z, separated by commas:

X coordinate, Y coordinate, Z coordinate

The Z coordinate can be omitted.

For instance, if we define a point with the absolute coordinates 30, 20, and 10, this means 30 absolute is in the X direction, 20 is in the Y direction, and 10 is in the Z direction.

Frequently, we want to specify a point in the coordinates, but one that is related to the previous point. The format for the relative Cartesian coordinates is defined by the symbol AT (@), followed by increment values in the three directions, separated by commas:

@X increment, Y increment, Z increment

Of course, one or more increments can be 0. The Z increment can be omitted.

For instance, if we define a point with relative coordinates, @0,20,10, this means in relation to the previous point, 0 is in X, 20 is in Y, and 10 is in Z directions.

When we want to specify a point but decompose it step-by-step, that is, separate its coordinates based on different locations, we may use filters. When prompting for a point, we access filters by digitizing the X, Y, or Z axes for individual coordinates, or XY, YZ, or ZX for pairs of coordinates. Another way is from the osnap menu, CTRL + mouse right-click, and then Point Filters. AutoCAD requests for the remaining coordinates until the completion of point definition.

Imagine that we want to specify a point, for instance, the center of a circle, where its X coordinate is given by the midpoint of an edge, its y coordinate is the midpoint of another edge, and finally its Z coordinate is any point on a top face. Assuming that Midpoint osnap is predefined, the dialog should be:

Command: CIRCLE
Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: .X
of midpoint of edge
(need YZ): .Y
of midpoint of edge
(need Z): any point on top face
Specify radius of circle or [Diameter]: value

The classic environment is based on the toolbars and the menu bar and doesn't use the ribbon. AutoCAD comes with AutoCAD Classic workspace, but it's very simple to adapt and view the suitable toolbars for 3D.

The advantages of using this environment are speed and consistency. To show another toolbar, we right-click over any toolbar and choose it. Typically, we want to have the following toolbars visible besides Standard and Layers: Layers II, Modeling, Solid Editing, and Render:

Since the 2009 version, AutoCAD also allows for a ribbon-based environment. Normally, this environment uses neither toolbars nor the menu bar. AutoCAD comes with two ribbon workspaces, namely, 3D Basics and 3D Modeling; the first being less useful than the second.

The advantages are that we have consistency with other software, commands are divided into panels and tabs, the ribbon can be collapsed to a single line, and it includes some commands not available on the toolbars. The disadvantage is that as it's a dynamic environment, we frequently have to activate other panels to access commands and some important commands and functions are not always visible:

If a correct layers application is fundamental in 2D, in 3D it assumes extreme importance. Each type of 3D object should be in a proper layer, thus allowing us to control its properties:

Last but not least, the best and the easiest process to assign rendering materials to objects is by layer, so another good point is to apply a correct and detailed layer scheme.

Transparency, as a property for layers or for objects, has been available since Version 2011. Besides its utility for layers, it can also be applied directly to objects. For instance, we may have a layer called 3D-SLAB and just want to see through the upper slab. We can change the objects' transparency with PROPERTIES (Ctrl + 1).

To see transparencies in the drawing area, the TPY button (on the status bar) must be on.

Another recent improvement in AutoCAD is the ability to hide or to isolate objects without changing layer properties.

We select the objects to hide or to isolate (all objects not selected are hidden) and right-click on them. On the cursor menu, we choose Isolate and then:

There is a small lamp icon on the status bar, the second icon from the right. If the lamp is red, it means that there are hidden objects; if it is yellow, all objects are visible:

Shown on the following image is the application of transparency and hide objects to the left wall and the upper slab:

Let's start with object snapping, probably the most frequently used tool for precision. Every time AutoCAD prompts for a point, we can access predefined object snaps (also known as osnaps) if the OSNAP button on the status bar is on. To change it, we only have to click on the OSNAP button or press F3. If we want an individual osnap, we can, among other ways, digitize the first three letters (for instance, MID for midpoint) or use the osnap menu (CTRL + right-click). Osnaps work everywhere in 3D (which is great) and is especially useful is the Extension osnap mode, which allows you to specify a point with a distance in the direction of any edge.

But what if we want to specify the projection of 3D points onto the working XY plane? Easy! If the OSNAPZ variable is set to 1, all specified points are projected onto the plane. This variable is not saved and 0 is assigned as the initial value.

More great news is that ORTHO (F8) and POLAR (F10) work in 3D. That is, we can specify points by directing the cursor along the Z axis and assign distances. Lots of @ spared, no?

OTRACK (F11), used to derive points from predefined osnaps, also works along the Z-axis direction. We pause over an osnap and can assign a distance along a specific direction or just obtain a crossing:

Starting with Version 2011, AutoCAD allows you to specify 3D object snaps. Also, here we can access predefined 3D osnaps keeping 3DOSNAP (F4) on, or we can access them individually. There are osnaps for vertices, midpoints on edges, centers of faces, knots (spline points), points perpendicular to faces, and points nearest to faces.

Using the LINE command, coordinates, and auxiliary tools, let's create a cabinet skeleton. All dimensions are in meters and we start from the lower-left corner. The ORTHO or POLAR button must be on and the OTRACK and OSNAP buttons with Endpoint and Midpoint predefined.

Basically, all drawing commands can be used in 3D, provided that we have the correct working plane, LINE being the exception.

The LINE command can have its endpoints anywhere, so it's a real 3D command. But circles, arcs, and polylines (including polygons and rectangles) are drawn on the working plane (called active coordinate system) or a plane parallel to the working plane.

Here is the list of the most important editing commands that work the same way in 2D or 3D: ERASE, MOVE, COPY, SCALE, JOIN, EXPLODE, and BREAK.

Some commands work only on the objects plane, not necessary the active working plane. Examples are FILLET, CHAMFER, and OFFSET.

There are also some that work only in relation to the active working plane such as MIRROR, ARRAYCLASSIC (ARRAY before version 2012), and ROTATE.

Next are editing commands that have special 3D features:

No one can use AutoCAD without inquiring for information from time-to-time. The DIST command allows you to obtain the 3D distance, and also increments in X, Y, and Z directions, between two points. Another important command is ID (or from the Tools menu bar, Inquiry | ID Point), for inquiring about the absolute coordinates of points.

Blocks work exactly the same way in 2D or 3D. When inserting a block with non-uniform scale, we can specify a different scale for the Z direction.

Regions are 2D opaque closed objects that are frequently used in 3D. Besides 3D, they can be very useful for extracting areas, inertia moments, and other geometric properties.

To create regions, we must have their contours already drawn. Contours can be lines, arcs, circles, ellipses, elliptical arcs, and splines. In 2D, regions are created with two commands:

We are going to create some 2D objects and from them, some regions.

Almost all linear entities that we know from 2D have a property called Thickness, whose value represents a height along the Z axis (a better word actually should be height). This is the only 3D feature available in AutoCAD LT and can be applied to text (if made with a text style that uses an SHX font), but beyond that is quite limited.

The best way to change the value of thickness is with the PROPERTIES command, Ctrl + 1. A line is still a line or a text still text, but with a proper visualization, these entities can transmit a 3D feeling:

Polylines created with the PLINE command are 2D, not allowing for vertices with different Z coordinates. These polylines are designed by lightweight polylines. But what if a single object is needed to be composed by segments whose endpoints have different Z coordinates?

The answer is to create 3D polylines. Three processes are available:

And in what situations may we have utility for 3D polylines?

3D polylines are particularly useful to measure objects that develop in different directions, such as piping or wiring, and to define paths for other 3D objects such as piping. The creation of 3D solids and surfaces from linear objects is the subject of Chapter 4, Creating Solids and Surfaces from 2D.

Splines are smooth linear objects, normally without corners that pass through or near specified points. Spline is short for Nonuniform Rational B-Spline (NURBS). Splines are described by a set of parametric mathematical equations, but have no fear, for AutoCAD will internally deal with this, we will not have to!

Splines are used whenever we need smooth curves and are also the foundation for NURBS surfaces, the most used surfaces in the automotive or aeronautic projects.

To create a spline we apply the (guess?) SPLINE command (alias SPL). By default, the command only prompts for the location of fit points, and the spline passes through the specified points. An Enter finishes the spline and the Close option creates a closed spline.

We can control splines by two sets of vertices:

When selected, the small blue triangle allows switching between Fit points and Control vertices. To edit a spline is very simple: we select it, without command, and work with grips. We can either click a grip and move it, or we can place the cursor over a grip and on the grip menu choose to move the vertex, add one, or remove that vertex. This last process is known as multifunctional grip.

With the HELIX command we can create 2D or 3D helixes or spirals. By default, the command prompts for the center point of the base, base radius, top radius, and height. As options, we have the position of the axis endpoint, the number of turns, the height of one complete turn, and the twist (if the helix is drawn in the clockwise or the counterclockwise direction). To edit a helix object, we can use grips or the PROPERTIES command.

If we explode a helix object, the result is a spline. The BLEND command, new in Version 2012, creates a special spline that connects two open linear objects. The command only prompts for the selection of the first curve and the selection of the second curve. Selections must be near the endpoints to connect. The Continuity option allows for the choice of the applied type of continuity: Tangent with a tangency continuity (known as G1 continuity), or Smooth with a curvature continuity (known as G2).