Transcript Oblique Drawing

CHAPTER 14
Pictorial Drawings and
Technical Illustrations
Learning Objectives
• Draw three-dimensional objects using
3-D coordinates
• Construct objects using isometric,
diametric, or trimetric methods
• Construct objects using oblique
drawing methods
Learning Objectives
• Draw objects using one-, two-, or
three-point perspective
• Apply a variety of shading techniques
to pictorial drawings
• Given an orthographic engineering
sketch of a part or assembly, draw the
part in pictorial form using proper line
contrasts and shading techniques
Pictorial Drawings
• Often accompany 2-D orthographic
multiviews
• Provide a realistic 3-D view
• Help improve visualization
• Now created using CADD or illustration
programs
• ASME Y14.4M, Pictorial Drawing
standard
Pictorial Drawings
• Useful for a variety of applications
• Clarify basic and complicated
engineering designs
• Help designers and engineers work out
spatial problems
• Most often the basis for technical
illustrations
Pictorial Drawings
Uses of Pictorial Drawings
• Design
• Instruction
manuals
• Parts catalogs
• Advertising
literature
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Technical reports
Presentations
Assembly
Construction
Isometric Projections and
Drawings
• Equal (iso) measure (metric)
• Simplest form of axonometric
projection
• Single scale for all axes
Isometric and Nonisometric Planes
Regular Isometric
• Most common
• View the top of the object and the
object from either side
Reverse Isometric
• View the bottom of the object
Long-Axis Isometric
• Common for long objects
Isometric Construction: Box or
Coordinate Method
• Most common form of isometric construction
• Used on objects that have angular or radial
features
Isometric Construction: Centerline
Layout Method
• Used on objects with many circles and arcs
• Circles in isometric are isometric ellipses
Isometric Circles and Arcs
Establishing Isometric
Intersections
Drawing Isometric Sections
Drawing Isometric Threads
• Equally spaced elliptical arcs
• Detailed thread representation
Drawing Isometric Spheres
Dimetric Pictorial Representation
• Form of axonometric projection
• Two different scales for measurement
• Missing image – go to page 566
Trimetric Pictorial Representation
• Most involved form of axonometric
projection
• Three different scales for measurement
Exploded Pictorial Drawings
• Exploded assembly
• Show the relationship of parts in a
realistic manner
• Commonly used in:
• Parts catalogues
• Owner's manuals
• Assembly instructions
Exploded Pictorial Drawings
• Isometric drawings most common
• Can include centerlines between part
and subassembly axes
• Can use solid extension lines between
non-cylindrical features, parts, and
subassemblies
• Can include balloons
Exploded Pictorial Drawing
Oblique Drawing
• Shows three faces of the object
• Useful if one face of an object needs
to be shown flat
Cavalier Oblique
Cabinet Oblique
General Oblique
Perspective Drawings
• Most realistic pictorial illustration
• Show depth and distortion perceived
by the human eye
• Objects appear smaller the farther away
they are until they vanish at a point on
the horizon
 One-point
or parallel perspective
 Two-point or angular perspective
 Three-point perspective
General Perspective Drawing
Concepts
One-Point Perspective
• Plan view is oriented so the front
surface of the object is parallel to the
picture plane
• Elevation view is placed below and to
the right or left of the plan and rests
on the ground line
• Used most often when drawing
interiors of rooms
Two-Point Perspective
• Two principal planes are at an angle to
the picture plane
• Two vanishing points provide another
dimension to the depth of the perspective
• Most popular form of perspective drawing
• Exteriors of houses and small buildings
• Civil engineering projects
• Machine parts (occasionally)
Three-Point Perspective
• Time consuming to construct
• Often occupy a considerable area on
the drawing sheet
• Used to illustrate objects having great
vertical measurements, such as tall
buildings
Drawing Circles and Curves in
Perspective
• Circles in perspective typically appear
as ellipses
• Any circle on surface parallel to the
picture plane appears as a circle
• Construction using the coordinate
method
Basic Shading Techniques
• Line-contrast
shading
• Straight-line
shading
• Block shading
• Stipple shading