Visualization and Design
Engineering Graphics
Stephen W. Crown Ph.D.
Objective


How to represent a 3-D object effectively on a
2-D drawing surface (pictorials)
How to visualize a 3-D object using solid
primitives
Overview
Sketching Review
 Pictorials

• Perspective
• Parallel projection

Other Visualization Tools
• Solid primitives
• Miscellaneous
Sketching (review)

Definition
A rough freehand drawing used to document,
communicate, and refine ideas developed
primarily in the ideation phase of the design
process
Follows standard practices
 A developed skill
 Should be the first step of any CAD or
mechanical drawing (including
homework assignments)

Pictorial Sketches


Definition: A sketch developed for ease of
visualization that shows an objects height,
width, and depth in a single view
Particularly useful for non-technical audiences
• Assembly drawings
• Marketing

Helpful in the ideation phase of the design
process
• How we picture objects in our mind
• How we visualize spatial relationships
Pictorial Sketches

Parallel Projection
•
•
•
•
Parallel lines are always drawn parallel
Easy to draw
Often appears distorted
Two common types
– Oblique Pictorials
– Isometric Pictorials

Perspective Projection
• Conveys information about distance and size
• Not as common as parallel projection
Parallel Projection Pictorials

Oblique Pictorials
• The simplest pictorial to sketch
• Surfaces which are parallel to the front face are
undistorted as in a multiview drawing
– Circular features should be placed in the front view if
possible
– Draw the front face first
• Lines which are perpendicular to the front face are
drawn at an angle of 30 to 45o
Parallel Projection Pictorials

Oblique Pictorials
• Cavalier Oblique
– Depth is drawn full size
– Object looks distorted (depth is exaggerated)
• Cabinet Oblique
– Depth is drawn to 1/2 of full size
– Depth appears more accurate (2/3 is best)
• Circular features which are not parallel to
the front plane appear elliptical
Axonometric Pictorials
• Trimetric
• no equal angles
• gives the most visually pleasing
view
• Dimetric
• Two equal angles
• Isometric
• Three equal angles (120o)
• Height drawn along vertical axis
• Width and depth drawn at 30o to
horizontal axis
• Other orientations (reversed and
long axis)
Parallel Projection Pictorials

Isometric Pictorials
• Most common
• Surfaces on all principle planes are
distorted
– All circles appear as ellipses
– Perpendicular lines are drawn at 60 or 1200
angles
• Height drawn along vertical axis
• Width and depth drawn at 30o to horizontal
axis
Parallel Projection Pictorials

Isometric Pictorials
• Begin drawing by blocking in height, width
and depth of entire object.
• Continue to block in smaller features
• Add curved surfaces last
– circles appear as ellipses
– lines tangent to arcs locate the edge of curved
surfaces
• Isometric grid paper is often helpful
– follow direction of axis and count intersections
– use tracing paper or grid paper with light lines
Isometric Projection and
Isometric Drawings
• Rotate about the Z axis 45o
• Rotate about the X axis by an angle of q=sin-1(2/3)½
• An isometric projection is a true size projection
½
 length along projected axes is L*(2/3)
• An isometric drawing is drawn full scale along axes
 objects are increased in size by a factor of (3/2)½
Perspective Projection Pictorials
The most difficult to draw
 The most visually accurate
 The use of vanishing points

• One point
– Lines of height and width are parallel
– Like a “perspective oblique”
• Two points
– Only lines representing height are parallel
– most common perspective view
• Three points
– No lines are parallel
Other Visualization Tools

Solid primitives
•
•
•
•
•
•
•
Box (Parallelepiped)
Cylinder
Cone
Sphere
Wedge
Extrude a 2-D shape
Revolve a curve about an axis
Other Visualization Tools

Operations on solid primitives
• Add
– assembly
– welding
• Subtract
– drilling
– milling/machining
• Intersection
– only regions where both part are in
common are retained
– helpful to produce mating parts
Other Visualization Tools

Right hand rule
• Your thumb, index finger, and middle finger
represent the X, Y, and Z axis respectively.
• Point your thumb in the positive axis direction
and your fingers wrap in the direction of
positive rotation
Other Visualization Tools
Always rotate parts using full 90 degree
rotations
 Number vertices in different views of
multiview and isometric drawing
 Practice
