WEBVTT

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>> This is a short lecture on
the basics of solid modeling,

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creating 3D solids
using AutoCAD.

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AutoCAD solid modeler
is primarily based

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on constructive solid
geometry or CGS which relies

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on the construction of
primitives or primitive solids

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which are nothing but simple
solids that are combined

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by Boolean operations
to form more complicated

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or composite solids.

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The general steps involved

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in constructive solid
geometry are --

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the first is construct
simple 3D primitive solids.

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Those are the ones are
either readily available,

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or you can create primitive
solids also from 2D shapes

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by converting them to 3D
solids using the operations

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of extruding or revolving.

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And then next step is
move this primitive

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in the correct relative
location relative to each other;

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and then apply Boolean
operations such as union,

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subtract, or intersect.

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Combine these primitives
to form a composite solid.

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So in our construction view we
will be following these three

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basic steps.

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And, if necessary, you might
need to make design changes

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to the features of
the composite solid

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by using solid editing commands.

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Primitives are nothing
but the basic building --

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basic building blocks that
make up more complex solids.

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Examples of primitives are box,
cone, cylinder, sphere, torus,

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wedge; and extrude and
revolve also will allow us

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to create primitives.

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Extrusion is an operation
that creates a solid

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from a two-dimensional
object by extruding

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or adding a Z dimension
to the closed 2D object.

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It has to be a 2D closed
object that is either a region,

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a circle, a polygon,
or a polyline.

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It is a sweeping operation
that allows the addition

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of a Z dimension to
your otherwise 2D shape.

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This command extrudes an
existing closed 2D shape

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such as a circle, polygon,
ellipse, polyline, spline.

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And only closed 2D
shapes can be extruded.

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There are two methods

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of determining the
direction of extrusion.

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By default, it is extruded
perpendicular to the plane

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of the 2D shape, or it can
also be extruded along a path.

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So in the default
method it just sweeps it

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in the Z direction linear sweep,

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but you can also get the
path of the sweeping.

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Revolving is another method
of creating a primitive solid

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from a 2D shape by revolving
about the selected axis.

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And the shapes that can be
revolved can be a polyline,

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a polygon, circle,
ellipse, or a spline.

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And one object at a
time can be revolved.

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Boolean operations are used
to combine the primitives

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to create more complicated
solids.

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Union simply joins the
selected solids together.

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Subtract subtracts -- subtract
subtracts one set of solids

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from another, so you can
have more than one solid

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in applying the subtract
operation.

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Intersection creates a solid
out of the intersection

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or the common volume
from the selected solids.

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After you have created
your solid,

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you can also edit
features of the solid.

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We have face options
for editing.

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We can change features
for the face as well

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as for the edge shown here as
options as well as body options

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from an existing solid.

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I will illustrate some
of the basic procedures

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of creating solid
models in AutoCAD.

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Let's start by changing
our workspace from drafting

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and annotation to 3D basics.

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This will show some of the
commands in 3D construction.

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Let's start by creating
a cylinder.

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We'll center this over here and
of this radius and a height 3.

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And then let's change
our view to SE Isometrics

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so we can see our solid
model being developed.

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Let's move that a little bit.

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And then the next thing I'm
going to do is I'm going

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to create a primitive,
this time a box,

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a rectangular box somewhere
here, the same width or depth

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as the cylinder and
then a height 1.

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Next thing I'm going
to do is I'm going

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to move this rectangular box
from its current location

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at the midpoint of this
edge here to the mid --

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the center of the cylinder.

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They're now in their
correct positions relative

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to each other.

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I'm going to union them

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which actually adds
the two solids together

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so that now it's just one solid.

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Let's create somewhere here
another -- another box, okay?

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So this size here,
also height 1,

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and then another cylinder here.

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Okay. We'll center it at
the midpoint of this edge.

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And the radius goes
to this corner here,

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this vertex also of height 1.

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And I'm going to union the two,
this cylinder and this box.

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Press Enter so that
there's only one.

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Next thing I'm going to do
is move this piece right now.

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Press Enter.

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With this base point on this
midpoint to the midpoint

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of this edge here, and
then I will subtract.

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This is the object
to subtract from.

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Enter. And then object

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to subtract is this
little thing here.

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And then we have our solid.

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So this is an illustration.

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It might be helpful to show
a different visual style.

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So you go to Visualize and
then select a conceptual

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which changes the way
it shows the solid.

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One problem -- one thing
that can be problematic

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for students is the creation of
the wedge, the primitive wedge.

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It goes according to AutoCAD's
logic for its orientation.

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Let me show you how it goes.

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Pick one corner of the
base, corner of the base.

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And that's the wedge in that
particular orientation based

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on our current UCS.

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Sometimes it's easier to create
your own wedge of, you know,

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a specified orientation just
by starting with a triangle --

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so that's the line command --

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and then turning this into
a region by region here.

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Select the three lines
here to create the region.

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Press Enter.

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Now it's a region, and those
three lines are combined

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together into one.

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And I can change that
into a wedge by extruding.