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Lec6BPictorial Drawings

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					Pictorial Drawings
Axonometric Projections
   Step by Step:
Isometric Sketching
                 Isometric Projection vs.
                         Sketch




Isometric projections are foreshortened because the object is tipped
with respect to the viewing plane. Isometric sketches are not usually
foreshortened because they still appear proportionate when showing
the dimensions full size along isometric axis lines. It is easier just to
sketch the full dimension.
                      Locating Features




To locate a feature such as the upper block, make measurements from an
existing corner as shown here.
                      Inclined Surfaces in
                            Isometric




Inclined surfaces can not be measured along inclined lines in an isometric
sketch. To locate inclined surfaces you must make measurements along the
isometric axis lines.
                Circles in Isometric
• Circles appear as ellispses
  when drawn in an
  isometric sketch.
• To sketch an isometric
  circle, locate the center
  and then sketch the box
  that would enclose the
  circular shape. Draw the
  ellispse tangent to the
  lines of the box.
Arcs in Isometric Sketches
                    Arcs are usually
                    sketched by
                    locating their
                    centers and
                    then boxing in
                    the enclosing
                    parallelogram.
                    Sketch the arc
                    tangent to the
                    enclosing box,
                    which is drawn
                    along isometric
                    lines.
Hidden Lines
         Hidden lines are not usually
         shown in isometric sketches
         unless they are needed to
         show a feature that would be
         unclear.
         Usually the orientation for
         the isometric drawing should
         be chosen so that hidden
         lines aren’t needed.
         Holes are assumed to go
         completely through the
         object unless their depth is
         indicated with a note or with
         hidden lines.
Exploded Isometric
    Assembly
           Isometric drawings are
           frequently used to show
           how parts assemble as
           in this automobile
           power module.
                     Oblique Pictorials




The advantage of oblique pictorials like these over isometric pictorials is
that circular shapes parallel to the view are shown true shape, making
them easy to sketch.
Oblique pictorials are not as realistic as isometric views because the
depth can appear very distorted. Oblique views cannot usually be
generated directly from a 3D model using CAD. It is primarily a sketching
technique.
     Unnatural Appearance of
        Oblique Drawing




Oblique drawings of objects having a lot of depth can appear very
unnatural due to the lack of foreshortening.
            Perspective Drawings
• Perspective drawings produce the view that is
  most realistic. A perspective drawing shows a
  view like a picture taken with a camera
• There are three main types of perspective
  drawings depending on how many vanishing
  points are used.
• These are called one-point, two-point, and three-
  point perspectives.
                 One Point Perspective




Orient the object so that a principal face is parallel to the viewing plane
(or in the picture plane.) The other principal face is perpendicular to the
viewing plane and its lines converge to a single vanishing point.
Terminology
                  One-point Perspective
                       Sketching
1. Sketch front
   surface of
    object and
    locate
    vanishing
    point.
                       Sketch receding lines

2. Sketch lines
   receding
    from
    intersections
    and points of
    tangency on
    front surface to
    vanishing
    point.
3   Estimate the
    depth of the
    object you will
.   show and
    block in the
    back surface
    between the
    receding lines.
Shading Techniques

				
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posted:9/23/2012
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