>> This is a short lecture on the basics of solid modeling,
creating 3D solids using AutoCAD.
AutoCAD solid modeler is primarily based
on constructive solid geometry or CGS which relies
on the construction of primitives or primitive solids
which are nothing but simple solids that are combined
by Boolean operations to form more complicated
or composite solids.
The general steps involved
in constructive solid geometry are --
the first is construct simple 3D primitive solids.
Those are the ones are either readily available,
or you can create primitive solids also from 2D shapes
by converting them to 3D solids using the operations
of extruding or revolving.
And then next step is move this primitive
in the correct relative location relative to each other;
and then apply Boolean operations such as union,
subtract, or intersect.
Combine these primitives to form a composite solid.
So in our construction view we will be following these three
basic steps.
And, if necessary, you might need to make design changes
to the features of the composite solid
by using solid editing commands.
Primitives are nothing but the basic building --
basic building blocks that make up more complex solids.
Examples of primitives are box, cone, cylinder, sphere, torus,
wedge; and extrude and revolve also will allow us
to create primitives.
Extrusion is an operation that creates a solid
from a two-dimensional object by extruding
or adding a Z dimension to the closed 2D object.
It has to be a 2D closed object that is either a region,
a circle, a polygon, or a polyline.
It is a sweeping operation that allows the addition
of a Z dimension to your otherwise 2D shape.
This command extrudes an existing closed 2D shape
such as a circle, polygon, ellipse, polyline, spline.
And only closed 2D shapes can be extruded.
There are two methods
of determining the direction of extrusion.
By default, it is extruded perpendicular to the plane
of the 2D shape, or it can also be extruded along a path.
So in the default method it just sweeps it
in the Z direction linear sweep,
but you can also get the path of the sweeping.
Revolving is another method of creating a primitive solid
from a 2D shape by revolving about the selected axis.
And the shapes that can be revolved can be a polyline,
a polygon, circle, ellipse, or a spline.
And one object at a time can be revolved.
Boolean operations are used to combine the primitives
to create more complicated solids.
Union simply joins the selected solids together.
Subtract subtracts -- subtract subtracts one set of solids
from another, so you can have more than one solid
in applying the subtract operation.
Intersection creates a solid out of the intersection
or the common volume from the selected solids.
After you have created your solid,
you can also edit features of the solid.
We have face options for editing.
We can change features for the face as well
as for the edge shown here as options as well as body options
from an existing solid.
I will illustrate some of the basic procedures
of creating solid models in AutoCAD.
Let's start by changing our workspace from drafting
and annotation to 3D basics.
This will show some of the commands in 3D construction.
Let's start by creating a cylinder.
We'll center this over here and of this radius and a height 3.
And then let's change our view to SE Isometrics
so we can see our solid model being developed.
Let's move that a little bit.
And then the next thing I'm going to do is I'm going
to create a primitive, this time a box,
a rectangular box somewhere here, the same width or depth
as the cylinder and then a height 1.
Next thing I'm going to do is I'm going
to move this rectangular box from its current location
at the midpoint of this edge here to the mid --
the center of the cylinder.
They're now in their correct positions relative
to each other.
I'm going to union them
which actually adds the two solids together
so that now it's just one solid.
Let's create somewhere here another -- another box, okay?
So this size here, also height 1,
and then another cylinder here.
Okay. We'll center it at the midpoint of this edge.
And the radius goes to this corner here,
this vertex also of height 1.
And I'm going to union the two, this cylinder and this box.
Press Enter so that there's only one.
Next thing I'm going to do is move this piece right now.
Press Enter.
With this base point on this midpoint to the midpoint
of this edge here, and then I will subtract.
This is the object to subtract from.
Enter. And then object
to subtract is this little thing here.
And then we have our solid.
So this is an illustration.
It might be helpful to show a different visual style.
So you go to Visualize and then select a conceptual
which changes the way it shows the solid.
One problem -- one thing that can be problematic
for students is the creation of the wedge, the primitive wedge.
It goes according to AutoCAD's logic for its orientation.
Let me show you how it goes.
Pick one corner of the base, corner of the base.
And that's the wedge in that particular orientation based
on our current UCS.
Sometimes it's easier to create your own wedge of, you know,
a specified orientation just by starting with a triangle --
so that's the line command --
and then turning this into a region by region here.
Select the three lines here to create the region.
Press Enter.
Now it's a region, and those three lines are combined
together into one.
And I can change that into a wedge by extruding.