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| Understanding Model and Paper Spaces; what you should know. (1) |
Introduction
After discontinuing the publication
of this series for a while, I’m glad to announce the final chapter of the Practising
AutoCAD— for All Levels (2D only) course, which I prepared and
dedicated to all who are in need of it the most, such as newly graduated architects
and to the architecture students and related specialties indeed… As the
majority of tutorials available in the market those days, don’t handle the essential
commands and tools that concern mainly architects and related professions, it
is being hard to find such very oriented and easy-to-learn courses though.
Therefore, and if you didn’t yet read
the previously published chapters in this series, I highly recommend doing so
now; afterward, you will have sufficient basic knowledge to perform any of AutoCAD’s
tasks that you might encounter in your career.
Anyway, here are the related links
sorted by order of knowledgeability:
As you already noticed, my course covers only the AutoCAD-2d so far, as the 3d is to
be discussed later within a more detailed section, to be published soon.
Besides,
what characterizes my tutorials from others is that they are very brief and
concise, as they go directly to the point, without twists
and turns. However, in this
chapter, we will be exploring some commonly used 3d tools —such as solid
modeling— to create some familiar solids, and we will need to demonstrate
their activity in the next example.
Understanding the Modeling Tools
Mainly, there
are two principal methods utilized in generating 3d models in AutoCAD but
they will be discussed later in more detail in the next chapter as I did
mention earlier; Those are Surface modeling and Solid modeling.
Anyway, if
we had to define each one of those two methods, we have to note the following:
- The surface modeling uses multiple faces connected to create geometric forms and models; for instance, a simple cube has to be created with six squares of faces connected via their edges. Likely, a pyramid is a composition of four triangular faces attached to the four edges of a square-shaped face which is its base.
- Solid modeling on the other side, adopts an easier method to create models, and it offers many advantages, especially in mechanical designs and engineering: It is a way of defining 3D objects as solid forms rather than wireframes with surfaces linked together.
When you are creating a 3D model using solid modeling
you start with the basic forms of your model like cubes, cylinders, or cones,
for example. Those basic solids are called primitives. Then using more
of these, you can start to add to or subtract from your basic forms. (Fig.1)
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| Fig.1- The solid primitives, Photo-source: flylib.com |
For example, to create the model of a tube, you first create
two solid cylinders, one with a smaller diameter than the other, and move
them so they’ll have their centers aligned. And then if we subtract the smaller
one from the largest one we will obtain a tube-shaped model. (See Fig.2)
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| Fig. 2- Creating a tube using solid modeling, Photo-source: flylib.com |
Similarly,
we can create an endless of geometrical forms and shapes by simply deducting
and adding them from each other.
How to Create Solid Forms?
As we noted
earlier, we will use the solid modeling method to create a simple model that we will need to demonstrate in the next exercise on using the layout in
our presentations.
In this
part, we will begin to draw the object shown in Fig.3. During the process, you
will explore the creation of solid models by using the various primitives
provided initially by the AutoCAD™ and then setting up special
relationships between its elements. Since it is
not our current target, we will be using the simplest architectural and geometrical model to accomplish our mission.
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| Fig.3- The volumetric building construction model that we will be modeling with the solid modeling tools, viewed with the Hidden Visual Style mode. |
Displaying the 3D Basics Workspace Panels
As advised, the first thing to do when working in the 3D modeling
space is to switch to the 3D Basics workspace located in the top-left
part of the UI, next to the quick commands bar (fig.4); It provides easy
access to all the basic 3d commands needed to create the solid primitives and
many of the tools you might use to edit them.
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| Fig.4- Displaying the 3D Basics Workspace with its related Panels |
The
indicated workspace can be picked among a list of other predefined workspaces
such as 3D Modeling, AutoCAD Classic, and Drafting and Annotation. By default, the
third is the workspace by choice if you’re working in 2D mode, but you can always
customize your list depending on your most-used commands and favorite tools, by
right-clicking any panels and deselecting or selecting the desired one to display
from the panels’ drop-down list.
By switching to
the 3D Basics Workspace, various panels with 3d commands make their appearance
at the top of the UI in a stacked row called the Ribbon menu. See
Figure 4 above for more clarification.
You are now
ready to start your first 3d session.
Creating Primitives
Primitives
are the basic construction blocks for solid modeling. At first, you might feel
that you are limited to having only six or eight primitives —depending on your ACAD’s version— to work with. But if you think further, you can imagine the
huge number of geometrical volumes that you can create by just joining,
substracting, and merging those primary forms.
So, let’s
begin by creating the basic support of our volumetric building, featuring a variety
of elements in a relationship with similar familiar architectural elements such
as the panoramic elevator, an expedition with a spherical structure dome, or
openings along the façade.
Prepare your
drawing for the exercise as follows:
2- In the Drafting Settings dialog box set the Snap spacing to 0.5 each and turn on the Grid and Snap modes by turning F7 and F9 on, respectively.
3- Turn on the dynamic input readout by pressing F12; Doing so, you will be able to type the given values on-screen to help you measure the lengths directly, required to accomplish the exercises that follow.
Likely, you can employ the ViewCube in the top-right corner of the drawing area, to generate the same preset views previously cited. (Fig.8)
Now begin to construct the suggested model:
1- Start the Box tool by typing Box in the command line, and start by entering the given width and length respectively (as per 7 x 9 units) when prompted as we proceed with the operation. So first, at the Specify corner of box or [Center] <0, 0, 0>: prompt, pick a point at the origin (0, 0) to locate the first corner of the model.
2- Likely, at the prompt that follows, type (@7,9), and by pressing enter you will create a box with a width of 7 and a length of 9.
3- At the Specify height: prompt that will appear next, you will have to enter a value of 2 as for the height of the box on the Z-axis.
Congratulations! You did by now
draw your first primitive, a box equal to (7 wide x 9 length x 2 height) units. (Fig.5)
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| Fig.5- The first primitive box is completed. |
Now let’s
try to change the view taken for the model so you can see the scene more
clearly from another angle; You can do this via several methods, among them is by typing _View in
the command line which initiates the View Manager dialogue box that
provides a list of Presets Views, featured with orthogonal and
isometric views, but mainly the isometrics views, based on the orthographic WCS (World Coordinates System) of the ACAD drafting system. (Fig.6)
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| Fig.6- The View Manager dialog box |
For
instance, selecting the preset SW isometric view will give us an
orthographic view from the SW corner defined by the following convention:
Another
useful conversion of the UCS accredited by the AutoCAD is to convert the X and
Y-axis into their geographical alternatives, i.e. the North, West, South, and the East direction that could replace the x and y axes as follows:
- The North direction represents the positive portion of the Y-axis,
- The South direction symbolizes the negative Y-axis,
- The West direction is the negative X-axis,
- And finally, the East direction is the positive portion of the X-axis. (Fig.7)
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| Fig.7- A schematic view showing an approach for the Preset Views |
Likely, you can employ the ViewCube in the top-right corner of the drawing area, to generate the same preset views previously cited. (Fig.8)
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| Fig.8- The Preset Isometric Views dialog box: SW, SE, NE, and NW Isometrics |
How to Convert a Closed 2D Polyline into a 3D Solid?
Here we can
proceed with the exercise in two different ways although they both lead to an
identical result. The first method consists of simply drawing the second solid wherever you want in the model space and then moving it to its appropriate final location.
But another method involves changing the position of the UCS to be able to model in place, without the need of moving the model later to its correct place.
Now let’s
add another geometric solid element, such as an L-shaped form with the second
method, which consists of changing the UCS origin to the top of the first drawn
element. To do so, we will simply type UCS in the command line and press
Enter. At the next prompt Specify
origin of UCS or [Face/NAmed/OBject/Previous/View/World/X/Y/Z/ZAxis]
<World>: we will pick on
the desired new point which is the coordinate (0,0,+2).
Name the
newly created UCS when prompted as new_UCS.
Also, you
have just defined the new working plan* for your new solid element to be
created.
(*) The working plan is the XY-plan where the modeling work takes place and where all the 2d commands are allowed to function correctly as the commands won't work properly if the objects aren’t coplanar.
In other terms, we have changed the Z-axis value of the WCS initially positioned at (0,0,0) to the new position with a positive Z-coordinate value equal to +2. This means a new UCS Origin inherited from (0,0,0) to (0,0,+2) as shown in Figure 9.
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| Fig.9- The new UCS position at the top of the box, and exactly positioned over the origin at the new coordinates (0,0,+2) |
This time we’ll create a new solid generated from a polyline. How is that? Let’s keep exploring…
1. Click the Polyline tool from the Draw Panel. You can either type PL in the Command-Prompt box for a similar procedure.
2. At the Specify start point: prompt, start your polyline from the point with the coordinates (+7,+9) which replaced the point (+7,+9,+2) as the current UCS is now new_UCS, defined earlier.
3. Then complete the remaining shape shown in Figure 10, and close the Polyline command when prompted to do so, by typing Close or just C, at the prompt Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
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| Fig.10- The Polyline is drawn in-place |
By doing so, you will ensure the creation of a closed polyline that only allows the usage of the command in the next step.
Use ACAD’s Polylines to help organize your lines and arcs into single entities and make them ready to accept several 3d tools not allowed to use in ordinary line objects.
Note that by selecting a polyline, the quick properties menu displays the Closed property section that allows you to turn it Yes or No. (The Quick Properties menu must be enabled first from the Drafting Settings dialog box or by pressing CTRL+SHIFT+P).
4. From the Create Panel, click on the Extrude button. Alternatively, you can type EXT in the Command-Prompt box.
5. At the Select objects to extrude or [MOde]: prompt, pick the last polyline that was drawn, and press Enter.
6. At the Specify height of extrusion or [Direction/Path/Taper angle/Expression] <0.0000>: prompt, type 10 and press Enter.
7. The polyline now extrudes in the Z-axis to form the model shown in Figure 11 below.
8. Now type RE to regen your screen and refresh your work.
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| Fig.11- The converted polyline box |
So far, you
have drawn two primitives’ boxes by using the Box and the Extrude
commands.
Just for variation,
this exercise had you create the second form by converting a polyline into a
solid, but you could just as easily have used the Box option for that as
well. Note that the Extrude option can convert closed polylines, 2d faces, regions,
and circles into solids. While 2d and 3d polylines and regular lines can be
converted into surface meshes, 3D Faces, and 3D polylines cannot be extruded
into solids.
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Other Primitives Options
Before
continuing, let’s explore the options for primitives that we haven’t had a
chance to use yet.
- The Cone draws a circular cone with a circular base; Drawing a circular cone is much like drawing a circle, with an additional prompt asking for a height.
- The Sphere acts like the Circle command, but instead of drawing a circle, it draws a sphere.
- The Torus creates a (donut-shaped solid). You
are prompted for two diameters or radii, one for the diameter or radius of the
torus and another for the diameter or radius of the tube of the torus.
- Wedge creates a wedge-shaped solid; This command acts much like the
Box command we used before. You have the choice of defining the wedge by two
corners or by its center and corner. Note that the wedge side is z-axis direction
sensitive; it is defined according to the rotation about the z-axis. Now,
knowing the basics, practice more to learn how it acts and to manipulate it!
In the next post, we will be creating and combining
solid primitives. The commands needed to create such complex solids are
available on the Edit Panel from the 3D Basics Workspace.
(Fig.12)
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| Fig.12- The Edit Panel from the 3D Basics Workspace list |
To be continued in the next post... So till then, stay safe and stay tuned.
Have a good day!
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References in this article:
1. https://flylib.com for some, illustrated and explicative photos.2. AutoCAD© 2002 Complete, Sybex Publications
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