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College of EngineeringEngineering Education Innovation Center

Orthographic Projection Basics

Chapter 10 of Text

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Objectives

• Discuss the principles of orthogonal projection

• Show how and why orthogonal projection is used to create multiple views of an object for formal engineering drawings

• Create a multiview drawing from a 3-D object

Note: The terms orthogonal and orthographic are used to refer to the same drawing type.

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Why Orthographic Drawings? • The best way to communicate what an object

looks like is to show someone an image. • Isometric sketches distort the features of an

object and may lead to misinterpretation.• Objects must be represented in a way that

prevents misinterpretation. • Multiview drawings show how an object looks

from multiple angles.• Multiviews help to prevent any mis-

communications that may happen when looking at only isometric pictorials.

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Orthographic Projections

• Orthographic projections are another way of representing a 3D object in 2D space.

• In an orthographic projection, the object is projected perpendicularly onto a viewing plane.

• By using a multiview drawing, we can eliminate misinterpretations that isometric views alone allow.

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Orthographic Projections• When drawing an

orthographic multiview, it sometimes helps to visualize the object inside of a glass box.

• Imagine that the object is projected on to each surface of the glass box.

• The box is then unfolded to form the multiview drawing.

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How Many Views Do We Need?• Just projecting one view of a surface isn’t

enough to completely describe the object

This single view can be interpreted in at least 6 different ways!

• To completely describe the object multiple views are shown.

• Generally, the front, top, and right side are sufficient to fully represent an object.

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Orthographic Projection• Use your snap cubes to build the following

object. • Look at if from the front, right, and top

sides.

Top

221

Front RightCLICK

Note: These are the 3 views associated with the object you just built.

Top

Front Right

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Orthographic Projections• Typically, the front, top, and right side

views are sufficient to fully describe an object.

Top

Front Right

Right

Top

Front

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View Alignments • In orthographic

projections, the views are aligned such that each point on the object is lined up with itself all three views.

• Each view shows two dimensions– Top: width and depth– Front: height and width– Right side: height and depth

A

A A

A

B

B

B

B

Hei

ght H

eight

Width

Width

Dep

th

Depth

Width

Height

Depth

CLICK

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Orthographic Projections

• Use this time and your snap cubes to practice building objects and sketching orthographic projections.

• In class assignment