WEBVTT

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>> Okay. This lecture is

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on orthographic projection
and multiviews.

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The orthographic projection
has this prefix ortho,

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which means perpendicular

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as in orthogonal planes
or orthogonal lines.

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They're perpendicular
to each other.

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Orthographic projection refers
to a system drawing views

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of a given object by
projecting points onto planes

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in the direction that's
perpendicular to the planes.

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So you have projection lines
that represent the line of sight

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and the line of sight
are perpendicular

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to the projection plane.

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As a result, the projection
lines are also perpendicular

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to projection planes.

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And this gives rise
what's called multiviews.

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Multi means many.

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So these multiviews are
two-dimensional views

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of an object projected
upon two or more planes

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of the projection
using orthographic

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projection techniques.

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Here's an illustration of
an orthographic projection

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that result into a view.

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We have a 3-D object
here in the back, okay.

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And we place a projection plane.

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In this case, it's in
front of the object.

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So it's called a
frontal projection plane.

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And then, we look at the
features such as vertices

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and edges of the given 3-D
object and project them

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into the projection
plane perpendicular

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to the plane itself and they
would trace an image here,

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as shown here.

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This little image on
the projection plane

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in this particular image
is called front view

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because it's projected
onto the frontal plane.

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Now if you do this to two
or more projection planes,

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you'll get multiviews.

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Here's an example of a
collection of multiview

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for exactly the same object
here but this time projected

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into three projection planes:
one that gives you the top view,

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another that gives
you the front view,

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another that gives
you right side view.

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And notice the placement
of these principal views.

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Front view is in the middle.

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The right side is always
to the right of the front.

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and the top is always
above the front.

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To illustrate this even further,

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let's consider this
three-dimensional object here,

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okay.

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We're going to use what's
called a glass box model,

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meaning we're going to put this
three-dimensional object inside

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a glass box.

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You see that thin outline of a
line that looks like an aquarium

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or a glass box that's
slightly bigger

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than the overall
dimensions of the object.

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So you put the object
inside the glass box, okay,

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such that the faces of the
glass box are parallel to some

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of the major surfaces of
a plane of the 3-D object.

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And then, the next thing
you do is you project, okay,

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the features through
orthographic projection

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of the object into each of
three projections planes:

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the top horizontal
plane, the frontal plane,

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and the right profile plane.

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So that's the orthographic
projection part of it.

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And then, what you do
is you remove the object

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and then you cut the glass box
along this edge right here,

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along the edges.

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And then, you open up the
box, okay, and then fold it

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to obtain the views, okay.

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This technique is called the
third-angle projection that's

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used in the US.

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For in the top is going
to be placed directly

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above the front view and
the ride-side view directly

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to the right of the front.

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So here's another demonstration
of the glass box as it unfolds

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after we cut it and open it.

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There we go.

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And take note, this
is now your top view.

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This is your front view.

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And this is your ride-side view.

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And notice the perfect alignment
of features in the top.

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Between the top and the front,
the front and the ride-side view

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and also between the right-side
view and the front view

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if we fold it back, okay.

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So I'll talk some more
about the multiviews, okay.

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We use common projection planes,

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also known as principal
projection planes,

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as we saw the frontal plane
giving you the front view,

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the horizontal plane, the top
horizontal plane giving you the

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top view, and the right profile
plane p giving you the right

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side view.

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And then, we cut the glass box
open to get the three views.

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But in addition to these three,

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sometimes you also have
the bottom of the box

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as your projection plane,

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the rear of the box,
or the left side.

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So you may have six
of them, six views.

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Dimensions are necessary in
order to define the object.

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So we have a three-dimensional
object.

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A three-dimensional object
has three dimensions obviously

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and the dimensions
are the height,

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the width, and the depth, okay.

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And as I mentioned earlier,
okay, these dimensions,

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the height dimensions
for instance,

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should be aligned perfectly

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between the two corresponding
views, the width dimensions

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between the top and
the front view,

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as well as the depth dimensions

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between the top and
the right views.

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If you notice some of the
lines that we saw earlier

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in our multiviews
are dashed, okay.

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They represent hidden
edges of the object.

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Okay, here's an illustration
of the alignment

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of the dimensions
in a multiview.

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Here's the width.

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And as you can see, the
width dimension is shared

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between the top and the front.

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Here's the height.

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It's showing in both the
front and the right-side view.

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And this is the depth, okay,
and it's shown in the top view

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and the ride-side view.

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And the way you check
the alignment is

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by using what's called
a miter line.

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This 45-degree line here is
a miter line to make sure

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that the depth, as it's
shown in the right side view,

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is exactly the same as the
depth shown in the top view.

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Vertical parallel
projections lines, right,

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should correspond features in
the top and the right-side view.

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Horizontal ones should
correspond alignment of features

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between the front
and the right side.

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How do you select which
one is the front view?

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The front view seems
to be the center view.

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As a general rule, you want the
front view to be as descriptive

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as possible representing
the most natural position

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of use of the object.

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And as a general rule,
okay, you select width

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as the longest dimensions,

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which should be shown
in the front view.

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Also, for it to be
most descriptive,

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you want to make sure
that the front view has

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as few hidden lines as possible,
hidden features as possible.

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Here's an illustration.

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This is the natural
position of this 3-D object.

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And we select this as the
front view, the number one,

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because it's descriptive
of the overall contour.

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The number two, it also captures
this biggest dimension of width.

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And here is an illustration
of the glass box model again,

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this time showing the six rather
than the three principal views.

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So you have the front view,
the right side view, top view.

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And then, we can also project
into the left plane here.

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The left profile plane will
give you the left-side view.

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You can project down into
the bottom plane, down here.

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That will give you
the bottom view.

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And there's a plane back
here you can project it

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to give you the rear view.

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And here's an illustration of
how you open your glass box

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if you want to show the
six principal views.

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Here's the front.

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But the way you add the three
other views are...

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the left should be to
the left of the front,

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the bottom is below the front,
and then the rear is actually

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to the left of the left.

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And notice the alignment of
the corresponding dimensions.

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Okay, selecting this as
the front makes sense,

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because it has the
widest dimension here.

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Representing the
right here is better

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than representing the left
because it's more descriptive,

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because this is shown
as a solid line

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from the right-side view here.

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Displaying here would be solid.

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On the other hand, from the
left, it becomes hidden.

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So it's better to use the
right compared to the left,

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at least for this object.

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In addition to solid lines
that represent visible lines

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of the object and
the hidden lines,

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that we also have seen
represented by dashed lines

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for the edges of the
object, are currently hidden.

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We also have centerlines
and we talked about this

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in week one lecture in
the alphabet of lines.

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Centerlines are generally
represented as long, short,

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sequence of long, short,
long, short dashes.

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And they're used to indicate
the positions of centers

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of all circles and arcs.

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And we have other types
of lines: dimension lines,

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extension or witness lines.

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Phantom, section,
and cutting planes,

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we'll talk about when we
get to sectional view.

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Here's an illustration
of hidden lines to show

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that this plane here, as viewed
from the front, is not visible,

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but the line inside the edges,
one on this side and one

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to this side, are still there,
but they're hidden, okay.

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Same thing here.

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The limiting element

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of the cylindrical hole will
be represented as hidden lines,

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both in the top and
the front view.

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Now notice also the center lines
here, long, short, long, long,

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short, long, okay,
representing the position

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of both the cylindrical hole
and the semi-circular part here.

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And here also, long,
short, long, long short,

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long in both directions.

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What this slide is indicating is

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that when you have a smooth
transition from a curved surface

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into a plane, there is no
line that separates those two

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because the transition
is smooth.

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On the other hand,
in a case like this,

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there should be a
solid line here, right,

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representing this edge here
or this skinny long plane here

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as viewed from the front.

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Line precedence, this is what
you will follow in terms of what

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and when to represent,

00:11:17.176 --> 00:11:19.446 A:middle
which type of line
whenever you have two

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or more lines coincidently
in the same position.

00:11:22.536 --> 00:11:25.136 A:middle
When one type of lines falls
in line with a different type

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of line, draw the line that
is most important based

00:11:28.616 --> 00:11:29.886 A:middle
on precedence.

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So object lines take precedence
over any other type of line.

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Now between hidden
line and centerlines,

00:11:38.606 --> 00:11:41.176 A:middle
hidden lines have
precedence over centerlines.

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So if you have a
position wherein hidden

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and centerlines should
both be there,

00:11:47.676 --> 00:11:48.846 A:middle
forget about the centerline.

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Hidden lines take precedence.

00:11:51.416 --> 00:11:53.496 A:middle
In sectioning, as you
will see later on,

00:11:54.106 --> 00:11:56.436 A:middle
cutting plane lines
take precedence also

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over centerlines.

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Different type of planes.

00:12:00.376 --> 00:12:01.446 A:middle
We talked about this.

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Indication of the relative
orientations with respect

00:12:05.406 --> 00:12:07.096 A:middle
to your projection plane.

00:12:07.626 --> 00:12:11.106 A:middle
A normal plane is one
that is parallel to one

00:12:11.106 --> 00:12:13.966 A:middle
of the three principal
projection planes,

00:12:14.466 --> 00:12:18.806 A:middle
either frontal, horizontal,
or profile plane.

00:12:19.516 --> 00:12:21.916 A:middle
And as a result, this
normal plane will be seen

00:12:22.486 --> 00:12:27.316 A:middle
in only one view as true
size and the other views,

00:12:27.316 --> 00:12:29.666 A:middle
it will just be an
edge or an edge view.

00:12:30.216 --> 00:12:33.716 A:middle
An inclined plane is
tilted with respect

00:12:33.716 --> 00:12:34.976 A:middle
to two principal
projection planes.

00:12:35.236 --> 00:12:38.916 A:middle
And as a result, it can
be seen in two views

00:12:38.986 --> 00:12:40.806 A:middle
but not in its true size.

00:12:41.316 --> 00:12:44.706 A:middle
On the other hand, an oblique
plane is one that is tilted

00:12:44.706 --> 00:12:47.246 A:middle
with respect to all the
principal projection planes.

00:12:47.626 --> 00:12:50.116 A:middle
And as a result, will
be visible but not

00:12:50.116 --> 00:12:52.936 A:middle
in its true size in
those three views.

00:12:53.136 --> 00:12:54.566 A:middle
Here's an illustration here.

00:12:55.666 --> 00:13:01.076 A:middle
The blue one, A, is parallel
to the frontal plane.

00:13:01.076 --> 00:13:03.176 A:middle
And as a result, you
see it in its true size

00:13:03.176 --> 00:13:05.166 A:middle
and shape in the front.

00:13:05.166 --> 00:13:08.036 A:middle
B is also normal
and it's parallel

00:13:08.036 --> 00:13:09.986 A:middle
to the top horizontal plane,

00:13:10.426 --> 00:13:13.446 A:middle
therefore it's showing
its true size in the top.

00:13:13.586 --> 00:13:16.806 A:middle
But if you look at the front,
it's on its edge as well

00:13:16.806 --> 00:13:18.186 A:middle
as the right side view.

00:13:18.736 --> 00:13:21.836 A:middle
C is another normal plane.

00:13:22.116 --> 00:13:24.036 A:middle
It's parallel to
the profile plane.

00:13:24.036 --> 00:13:25.416 A:middle
You see the true size here.

00:13:25.816 --> 00:13:29.726 A:middle
However, C is only shown on
this edge here, in the front,

00:13:29.726 --> 00:13:34.406 A:middle
and also on its edge,
the top view.

00:13:34.406 --> 00:13:36.206 A:middle
D is an example of
an inclined line.

00:13:36.206 --> 00:13:39.206 A:middle
As you can see, it's shown
as planes in two views,

00:13:39.706 --> 00:13:45.206 A:middle
top and the horizontal and
the top and the right explains

00:13:45.206 --> 00:13:49.316 A:middle
that therefore the sizes of
D here, shown in the views,

00:13:49.696 --> 00:13:53.156 A:middle
are actually smaller than
the actual true size in D.

00:13:53.596 --> 00:13:55.326 A:middle
And D is shown as an edge

00:13:55.616 --> 00:13:57.076 A:middle
and that they're
viewed at the front.

00:13:57.726 --> 00:14:03.096 A:middle
An example of an oblique plane
is E. And as you can see,

00:14:03.166 --> 00:14:07.976 A:middle
E is shown as the planes end,
as the plane in the three views.

00:14:08.556 --> 00:14:12.256 A:middle
But none of the three views is
showing its true size and shape.

00:14:13.806 --> 00:14:17.216 A:middle
Sometimes when we're trying
to visualize 3-D objects,

00:14:17.216 --> 00:14:20.366 A:middle
in order to determine how
to represent them in views,

00:14:20.366 --> 00:14:24.926 A:middle
it might be useful to label
planes, plane a, plane b,

00:14:24.926 --> 00:14:27.066 A:middle
plane g, for instance,

00:14:27.066 --> 00:14:30.396 A:middle
so you can easily
locate them in the views.

00:14:30.746 --> 00:14:35.936 A:middle
In others, okay, it might even
be better to represent lines

00:14:36.146 --> 00:14:39.156 A:middle
and label line and vertices.

00:14:39.436 --> 00:14:43.556 A:middle
For instance here,
point three, four, five,

00:14:43.556 --> 00:14:49.836 A:middle
six actually represent plane
C. Here's another illustration

00:14:50.486 --> 00:14:53.956 A:middle
of labeling of surfaces
and planes.

00:14:54.496 --> 00:14:58.856 A:middle
Here's an example of
labeling vertices and lines.

00:15:00.086 --> 00:15:06.876 A:middle
For labs number 4A and 4B, you
will be given a 3-D object,

00:15:07.456 --> 00:15:10.486 A:middle
okay, and you will be
asked to sketch on paper

00:15:10.486 --> 00:15:14.156 A:middle
and pencil the three principal
views: top, front, right.

00:15:14.496 --> 00:15:16.606 A:middle
You will have a second
part wherein you're going

00:15:16.606 --> 00:15:19.746 A:middle
to be creating multiviews
in AutoCAD.

00:15:20.306 --> 00:15:23.506 A:middle
And when you do that
in AutoCAD, okay,

00:15:23.536 --> 00:15:27.036 A:middle
it's best to group entities
together into layers.

00:15:28.146 --> 00:15:30.266 A:middle
All the object lines
should go to layers.

00:15:30.266 --> 00:15:32.056 A:middle
Now layers-- What is a layer?

00:15:32.706 --> 00:15:37.246 A:middle
A layer is a way of grouping
entities, entities meaning lines

00:15:37.246 --> 00:15:39.146 A:middle
and arcs and objects, together.

00:15:39.666 --> 00:15:44.676 A:middle
If you imagine seeing an
architect using tracing paper,

00:15:44.946 --> 00:15:46.486 A:middle
tracing paper is
kind of transparent,

00:15:46.946 --> 00:15:50.236 A:middle
an architect may use
many different papers

00:15:50.236 --> 00:15:54.146 A:middle
for different parts
of the plans.

00:15:54.146 --> 00:15:56.976 A:middle
So for instance, you might
have a layer or a paper

00:15:56.976 --> 00:16:00.326 A:middle
for electrical, another
one for the walls,

00:16:00.836 --> 00:16:03.486 A:middle
another one for furniture,
and so on and so forth.

00:16:03.486 --> 00:16:06.956 A:middle
So you can view each layer
individually if you want

00:16:06.956 --> 00:16:10.066 A:middle
or you can overlay the
layers together if you want

00:16:10.066 --> 00:16:12.816 A:middle
to see how they fit well
connected to each other.

00:16:12.816 --> 00:16:15.466 A:middle
And that's the whole
idea behind layers also.

00:16:16.606 --> 00:16:19.306 A:middle
So you will have a layer
for all the object lines,

00:16:19.306 --> 00:16:22.256 A:middle
for all the hidden lines,
for all the section lines

00:16:22.256 --> 00:16:24.436 A:middle
and hatching associated
with sectional views,

00:16:24.906 --> 00:16:27.186 A:middle
texts and dimension, and
maybe for title border.

00:16:27.186 --> 00:16:29.926 A:middle
So for instance, if I just want
to see all the object lines

00:16:29.926 --> 00:16:32.726 A:middle
without the other
details, I'll turn this on

00:16:32.896 --> 00:16:34.646 A:middle
and turn off the rest of them.

00:16:35.786 --> 00:16:40.816 A:middle
And then, the next step is
after you've created the layers,

00:16:41.136 --> 00:16:46.536 A:middle
you create basic construction
lines representing the overall

00:16:46.536 --> 00:16:49.676 A:middle
outline of the front, top,
and right-side views, okay,

00:16:49.676 --> 00:16:51.466 A:middle
using third angle projection.

00:16:51.866 --> 00:16:56.546 A:middle
Again, front and the middle,
right to the right of the front,

00:16:56.596 --> 00:16:59.636 A:middle
and top above the front, okay.

00:16:59.706 --> 00:17:02.816 A:middle
And make sure that you
observe appropriate spacing

00:17:02.816 --> 00:17:03.916 A:middle
between the views.

00:17:04.516 --> 00:17:08.466 A:middle
Then, you start creating
construction lines in order

00:17:08.546 --> 00:17:12.786 A:middle
to locate height dimensions
between the front view

00:17:12.786 --> 00:17:13.866 A:middle
and the right-side view.

00:17:14.176 --> 00:17:16.676 A:middle
Those will be horizontal
construction lines

00:17:17.436 --> 00:17:23.366 A:middle
and then vertical construction
lines to align dimensions

00:17:23.366 --> 00:17:26.216 A:middle
of width between the
front and the top.

00:17:26.666 --> 00:17:28.706 A:middle
And then you use the
miter line in order

00:17:28.706 --> 00:17:32.536 A:middle
to transfer depth measurements,
okay, between the top view

00:17:32.806 --> 00:17:34.706 A:middle
and the right-side view.

00:17:34.706 --> 00:17:39.296 A:middle
And then from there, it might
be a good idea to start locating

00:17:39.296 --> 00:17:43.276 A:middle
on the planes and start
representing those normal planes

00:17:43.276 --> 00:17:47.106 A:middle
with object lines, okay and
then work on the inclined

00:17:47.496 --> 00:17:50.916 A:middle
and then work on
the oblique planes.

00:17:50.916 --> 00:17:53.836 A:middle
Once you have all the
following lines figured out,

00:17:53.876 --> 00:17:57.316 A:middle
you can now start
looking for hidden lines

00:17:57.316 --> 00:18:01.166 A:middle
and then add other types of
lines, such as centerlines

00:18:01.586 --> 00:18:03.136 A:middle
for all circles and arcs.

00:18:03.996 --> 00:18:06.586 A:middle
Whenever you have a
coincident of line,

00:18:06.896 --> 00:18:10.436 A:middle
make sure that you
can follow our rules

00:18:10.436 --> 00:18:12.696 A:middle
for precedence of lines.

00:18:14.036 --> 00:18:17.516 A:middle
And then optional, add
dimensions and texts,

00:18:17.516 --> 00:18:19.716 A:middle
at least for some of the labs.

00:18:20.196 --> 00:18:23.616 A:middle
Dimensions are and
texts are optional.