4.01 Principles of Sketching and Visualization
Sketching is an important communication tool, a traditional means of documenting
ideas, and an important way to communicate ideas to others. It is a problem-solving tool to
visualize how elements relate to each other and work together. The possibilities in sketching
range from quick thumbnail sketches to documenting an idea with full color and renderings
that accurately represent an object with photographic-like realism. It is important to
recognize that ideas that exist in the mind can be communicated through the process of
sketching. The geometry of a sketch consists of lines, circles, ellipses and polygons.
There are specific rules to remember when sketching as well as useful techniques.
1. Hold the pencil about 1-½ inches from the tip at a 50 to 60 degree angle.
2. Right-handed move from left to right. Left-handed move from right to left.
3. Rotate paper to facilitate natural ease of drawing.
4. Vertical lines are drawn from top to bottom.
5. Long lines are generated by the using short lines that do not overlap.
6. Make lines parallel to edge by using a finger sliding on edge to control it.
7. Practice making circles using a fingernail as a compass (pivot) point while rotating
paper under it. Circles and arcs can be generated using bisected squares as construction
guides.
8. Use very lightly drawn preliminary target points to create shapes. Try point-to-point
method for determining proper length and placement.
9. For ellipses use bisected rectangles as construction guides.
A picture can explain an idea better than a lot of words. Most of today’s languages began
as pictures. Many occupations such as architecture, electronics, engineering, mapping and
topography use several types of drawings. The four basic types of drawings include:
sketches, illustrations, multi-view drawings, and pictorial drawings. (R5, pg. 162)
4.01 Principles of Sketching and Visualization
A multi-view or working drawing is a two-dimensional drawing of a three-dimensional
object. They are the most common drawing used in industry. This type of drawing allows for
an object to be viewed from several different angles. These angles are referred to by industry
as views. There are six different views of an object. This is easily understood when an object
is placed in a transparent box. Each of these views is created by simply projecting them onto
the box’s sides and unfolding them to create a flat two-dimensional surface. Multi-views are
created using a technique called orthographic projection. In orthographic projection, the
different views are drawn at right angles or perpendicular to one another. There are six
planes of projection that correspond to the sides of the transparent box. The six views are:
top, bottom, front, back, right-hand side, and left-hand side. Typically multi-view or
Orthographic drawings are constructed from three views: top, front and right or left-hand
side. It is not necessary to include more than three views unless the object you are drawing
has additional information that needs to be communicated.
Figures produced using ProDesktop 2000i.
The drawing on the left is an isometric and the one
on the right is a multiview of the same object.
Pictorial Drawings are viewed in such way that several faces appear in a single view.
This gives the illusion that the object is three-dimensional even though it is drawn on a twodimensional surface. The three most common pictorial drawings are: isometric, oblique and
perspective.
4.01 Principles of Sketching and Visualization
Isometric drawings are based on three lines or axes, which are equally spaced at 120
degrees apart. The word isometric means “of equal measure.” The drawing is created by
rotating the object with the left or right corner on the front of the object faces you. Next, tilt
the object forward so that the top surface is seen creating three lines that are equally spaced.
The main lines that makeup these edges are drawn at 30 degrees. In isometric sketches or
drawings, circles appear as ellipses and can be drawn using the rectangular method or ellipse
templates.
Oblique drawings have a front face that is drawn as if it is viewed straight-forward. The
top and side faces are drawn at an angle of 30 degrees or 45 degrees to the horizontal.
30 or 45
degrees
4.01 Principles of Sketching and Visualization
The front of an oblique drawing always shows the true shape of the object from a head-on
view. They are two types of oblique drawings, cabinet and cavalier. The difference is the
cabinet is drawn at one-half the depth of the objects true depth while the cavalier is drawn at
true depth.
Cavalier
Cabinet
Depth is
true
size.
Depth is ½
the original
size.
Perspective drawings are the most realistic of all the pictorial drawings. The object appears
three-dimensional by using four factors.
(1) The position of the viewer relative to the object drawn.
(2) How the object is drawn from the ground line to the vanishing point. The vanishing
point is the point where the lines meet in the distance.
(3) The position of the vanishing point should always be located on the horizon line.
(4) The complexity of the object and its detail. (R5, pg. 170)
4.01 Principles of Sketching and Visualization
There are three types of perspective drawings: one-point, two-point and three-point.
One-points are the most common and are generally used by artist. Architects and product
illustrators use the two-point perspectives. And three-point are limited to the field of
commercial art.
Shading is a technique commonly used in technical illustrations. This shows the object
in shadow and light as it would normally appear in its natural setting.
The sun and ceiling lights are typical overhead sources. In technical illustration light
sources normally appear in the upper left corner, shining on the object, Fig. 4-1. The surfaces
that face the light source will have no shading, while the surfaces away from the source are
shaded. The shadow is cast from the object on the opposite side of the light source. The
direction of the shadow is the same direction of the light source. Fig. 4-3 shows the light
source from the upper right corner behind the chess piece. The light source in Fig. 4-2 shows
a source from the left side of the sphere. The right and left orientation of the light source is
not as you view the illustration but from the sources view point.
Fig. 4-1
Fig. 4-2
Fig. 4-3