3 Visualization

Visualization

  • PERSPECTIVE
  • OBLIQUE DRAWING
  • ISOMETRIC DRAWING
  • ONE-VIEW DRAWING
  • TWO-VIEW DRAWING
  • ORTHOGRAPHIC PROJECTION
  • HIDDEN SURFACES
  • CURVED SURFACES
  • INCLINED SURFACES

Now that you have learned about the kinds of lines found on prints, the next step is to develop your visualization abilities. The ability to ”see” technical drawings; that is to ”think in three dimensions,” is the most important part of this course. Since most engineering and architectural prints utilize some form of orthographic projection (multi-view drawing), that type of drawing will be emphasized.

Before going into a study of orthographic projection, you should be able to recognize several other types of drawings. They are; 1. Perspective drawing, 2. Oblique drawing, and 3. Isometric drawing. As a group, they are called “pictorial drawings”. They are found on prints and are easy to visualize, so let’s look at their differences.

Perspective

Perspective is the most realistic form of drawing. Artists use one-point perspective, two-point (shown here), and three point to create visual depth. Perspectives are used by architects and for industrial pictorials of plan layouts, machinery, and other subjects where realism is required. Objects drawn in perspective grow smaller as they recede into the horizon.

Geometric solid in 2 point perspective. The image is a black and white diagram illustrating two-point perspective in drawing. It shows a 3D shape, similar to a rectangular block, receding into two vanishing points on the horizon line. The horizon line is horizontal, spanning across the top of the image. Lines converge towards each vanishing point from the edges of the block. The vanishing points are labeled "VP" at both ends of the horizon line. The diagram demonstrates how perspective affects the appearance of objects in space.

Oblique

Oblique drawings are drawn with one plane (front) of the object parallel to the drawing surface. The side, or other visible part of the object is generally drawn at 30◦ or 45◦. Note that only the side is on an angle. Many times these types of drawing are not drawn to scale.  The receding lines are drawn at 45◦ or 30◦ and will be drawn at a different scale as the vertical and horizontal lines.  This make the drawing seem “out of shape”.  This type of drawing is not used very often in industry.

Geometric shape drawing on oblique 30 or 45 degree angles. The image depicts a simple diagram of a three-dimensional geometric shape resembling stairs, commonly used to demonstrate oblique drawing techniques. The shape has three visible faces: the front, the top, and the right side. An arrow points to the diagonal projection and is labeled "30° OR 45°", indicating the angle commonly used in oblique drawings. Another arrow points to the shape itself, labeled "OBLIQUE DRAWING."

Isometric

Isometric drawings have less distortion than oblique drawings, and are used more frequently by industry for that reason. An isometric drawing has both visible surfaces drawn at 30◦. These are the most used type of drawings in the piping industry and take a good deal of practice to fully understand how to draw.  They best represent what is being built and what it will look like from the different sides with one drawing.

 

Geometric solid drawn isometrically. The image is a black and white isometric drawing of a three-dimensional geometric shape resembling two rectangular blocks stacked in a step-like arrangement. The shape consists of a lower rectangular block and a higher one on the right. The lines defining the blocks are solid and clear. Two 30-degree angles are indicated at the base, showing the orientation of the shape in space. The text "ISOMETRIC DRAWING" is positioned to the right of the shape.

 

Directions: Name the types of drawings shown below. Check your own answers.

Geometric shapes for the student to identify. The image features a series of five isometric shapes, each resembling a three-dimensional block structure. The shapes are numbered from 1 to 5 with arrows pointing to each one, suggesting an ordered sequence or labeling system. The first shape is composed of three stacked cubes forming an ascending staircase-like structure. The second shape, similar in structure, consists of three stacked cubes but arranged in a uniform vertical alignment. The third shape is a V-shaped arrangement of blocks, appearing to have a notch or indentation in the middle, creating two protruding arms. The fourth shape consists of two cubes side by side with a third cube placed on top of the left cube, forming an L-shape. The fifth shape resembles a right angle made by placing one cube on top of another cube, forming a corner structure. The shapes are outlined with thin black lines against a plain white background.

 

Single View 

A single view of an object is sometimes all that is needed for a complete visual explanation. When dimensions, material, and other information is Included, an object requiring only a single view is easy to understand.

Most one-view drawings are of flat objects, made from materials such as sheet metal and gasket stock.  Spherical objects, such as a cannonball, would require only one view and a note indicating the material and diameter of the sphere.

The object shown in the one-view drawing below could be made of any appropriate material that might be specified. In appearance, it is much like the gasket used as part of the cooling system on many cars. All that would need to be noted is the material type and thickness required.

Drawing of a gasket needing only 1 view. The image is a technical drawing of a gasket with three main circular sections arranged horizontally. The central circle is the largest, with a labeled diameter of 3.50 units, while the two smaller circles are at each end with a labeled diameter of 1.00 unit each. They are connected by two symmetrical arcs on either side, creating an oblong shape. The drawing also includes labeled measurements: two radii specified as R2.50 for the arcs connecting the circles and another radius R1.40 for an outer boundary. An overall length of 6.00 units and a central dimension of 3.00 units are marked at the bottom. The word "GASKET" is written near the lower right part of the drawing.

 

Two View

Sometimes “two-view” drawings are use on prints. Two views may be all that is needed to show the shape of an object. Objects that are cylindrical, such as a length of pipe, are usually shown on a print with two views. In such a case, two views is sufficient to explain the shape. Notice in the two-view drawing shown below that the length of the pipe is shown in one view, while the diameter is called out in the other. Without the view on the right, what might this shape be mistaken for?  Square tube, channel…

 

Front and end view of a dimensioned section of a pipe. The image is a technical drawing depicting a cylindrical object, such as a pipe, from two perspectives: a side view on the left and an end view on the right. In the side view, the object is represented as a rectangle with two horizontal dashed lines inside, indicating the hollow interior. The dimensions show a width of 3.72 units. The end view shows a circle with a diameter labeled as 1.50 units, indicating the inner dimension of the cylinder. The drawing includes a leader line pointing to the circle with the dimension noted. The material specification is noted below the circle as "MAT’L: W.I. PIPE".

 

Orthographic Projection

Orthographic projection is a name given to drawings that usually have three views.  Often, the three views selected are the top, front, and right side. It is possible, of course, to select other views such as the left side or bottom. Generally, though, it’s the top, front and right side that are traditionally seen by the person reading prints.

Since most prints make use of the orthographic projection system, and because the top, front, right side views are most often used, it is important that you have their order, or arrangement on the print fixed in your mind. To help you understand this system, think of a chalkboard eraser, a short length of 2″ x 4″ lumber, or a common brick. It looks like this:

 

The image depicts a simple three-dimensional line drawing of a rectangular prism, oriented in a way that three of its faces are visible: the front, top, and right side. The drawing is presented in black lines on a white background. Arrows point to each visible face, with accompanying text labels identifying them as "FRONT," "TOP," and "RIGHT SIDE."

 

When seen on a print, using orthographic projection, it would appear like this.

3 orthographic views of a single part. The image depicts a simple engineering drawing with three labeled views of a geometric object. There are three rectangular outlines: one at the top labeled "TOP VIEW," one at the bottom left labeled "FRONT VIEW," and one at the bottom right labeled "RIGHT SIDE VIEW." Each rectangle is labeled with lines pointing to them, indicating their respective view.

This system of orthographic projection may be difficult to understand or visualize at first, but you will grasp it with some practice. Here’s a basic example of how it works, using a simple object.

Orthographic view of a block identifying the individual views. The image is a line drawing of a three-dimensional object, depicted to illustrate different views: front, top, and right side. The object resembles an L-shaped block with two levels. The lower level is a larger rectangular block, while the upper level is a smaller rectangular block positioned on top of the right-hand side of the lower block. Arrows point to different sides of the object, labeling the views: "FRONT VIEW" on the left, "TOP VIEW" on the upper side, and "RIGHT SIDE VIEW" on the right. The drawing includes text indicating these views.

 

Orthographic projection does not show depth, so the object shown above will appear flat. With practice, however, you will learn to scan the three views and “read” depth into them. Remember that the location of the top, front and right side views does not change. The projection lines between the orthographic views below show the height, width, and depth relationship that exists between each view and the other two views.

 

Explaining the 3 view orthographic layout of a part The image displays a technical drawing layout on a rectangular white background. It features three views of an object, separated by horizontal and vertical projection lines. In the top left quadrant is a rectangle labeled "TOP VIEW." Below this, on the left, is a larger rectangle labeled "FRONT." To the right of the front view is a smaller rectangle labeled "RIGHT SIDE." A diagonal projection line connects the top view to the right side view, with a label "PROJECTION LINES" and an arrow pointing to the lines. The layout follows a standard engineering drawing format.

 

In case you did not understand the three-view on the last page, let’s take another look at the same thing. This time numbers will be used for identification for the surfaces.

 

Isometric view of a geometric shape with labels indicating the associated views. The image displays a three-dimensional geometric shape resembling a staircase with two steps. This shape is composed of multiple rectangular blocks, each labeled with a number from 1 to 5. The largest block, labeled "1," forms the base. On top of this is another block labeled "2" that creates the higher step. The surface upon which one would step if ascending the stairs is labeled "4," and the surface of the lower step is labeled "3." The rightmost face of the lower block is labeled "5." The lines are drawn in black, and the numbering is displayed across each face.

Using orthographic projection, the object with the surfaces numbered appears like this:

 

Orthographic layout of the previous isometric shape. The image is a white rectangular canvas with five numbered rectangular and L-shaped figures, each outlined in black. In the upper left area, two adjacent rectangles labeled "2" and "3" form a wider rectangular block. Below them, an L-shaped figure labeled "1" is positioned in the lower left part of the canvas. On the right side, there is a vertically stacked pair of rectangles labeled "4" on top and "5" at the bottom.

 

Notice that the front view (1) is the key to the drawing, because it most clearly shows the shape of the object. It tells you the object is “L” shaped from the front. The other two views don’t tell you much by themselves. By looking at surface 1, however, you can see that 2 is taller than 3. Therefore, in “reading” the surfaces, 2 should appear to be closer to you than 3. Now look at 4 and 5. Which surface is projected closest to you?·

Answer: Surface 5 (rotate and place at bottom of layout)

 

Now draw a simple box and tape all sides together to form a cube.  The cube will be 2”x 2”x 2”. Once the instructor has approved your drawing you will proceed to cut out and tape edges together to form a cube.

Visualization Quiz

Directions:

All visible surfaces on the objects shown are numbered. To complete this quiz, you are to place those numbers on the corresponding surfaces of the orthographic drawings.

Geometric shape with numbers on each face. The image displays an isometric and orthographic projection of an L-shaped object. The top section includes an isometric view of a 3D L-shaped block. The block has five numbered rectangular faces. The front and side perspectives are labeled. Below, the orthographic projections are shown. The top view shows an L-shape, the front view shows two joined rectangles, and the side view shows two vertical rectangles.

 

 

Isometric view of a geometric shape with numbered faces for identification. The image shows a diagram consisting of geometric shapes and their unfolded views in two distinct sections. At the top is an isometric drawing of a rectangular prism labeled with the numbers 1 through 6, representing each face of the prism. Below, there are three rectangles arranged in a grid on a white background. The first rectangle on the top left is an L-shape. The second, on the bottom left, is divided into two squares, one smaller than the other. The third is a single tall rectangle with a smaller portion inside aligned to the right.

 

Isometric view of a geometric shape with surfaces numbered for identification. The image is divided into two parts. The upper section features an isometric drawing of a three-dimensional structure formed by stacking rectangular blocks. The blocks are numbered 1 to 8 and stacked in a right-angled shape. Block 4 forms the base, supporting blocks 1, 2, and 7. A second vertical stack includes blocks 3, 8, and 4. The lower section contains outlines of the blocks, presented in various orientations across a large rectangular area. The shapes are laid out separately, illustrating different perspectives or combinations of the blocks.

 

You may be wondering at this point why something like orthographic projection is used on prints when isometric or oblique drawings are so much easier to visualize. The answer is that both of those types of pictorials are used for relatively uncomplicated drawings. When an object is complex, however, neither can equal the orthographic system for clear presentation of dimensions, notes, and configuration details.

 

Hidden Surfaces

Another advantage of orthographic projection is that it allows the person reading the print to have the ability to see the inside, or surfaces of an object which normally could not be seen.

With complicated objects this can become very useful.

In the drawing below, the hidden line in the right side view represents the entire surface of the flat area between the two higher sides.

Geometric shape with hidden faces. The image illustrates a three-dimensional geometric shape alongside its orthogonal projections. The top right corner features a 3D L-shaped object. The object is composed of two connected rectangular prisms, with a notch cut out of one side to form an L-shape. Arrows labeled "TOP," "FRONT," and "SIDE" indicate the corresponding views on the 2D projections below. The central part of the image displays three separate rectangular outlines depicting the top, front, and side views of the object. Each view is labeled accordingly. A dashed line in the side view represents a hidden surface. Lines connect the 3D shape to its corresponding 2D projections.

 

 

In this example, the hidden lines result from a square hole through the middle of the object.

Geometric shape with center removed. The image displays a technical drawing with multiple views of a three-dimensional object featuring a square hole in the center. In the top left, there is a top view showing a horizontal rectangle with two dashed lines indicating the position of the hole. Below it, the front view displays a square with a smaller square hole in the center, labeled "SQUARE HOLE." The side view, to the right of the front view, shows a vertical rectangle with two dashed lines, representing the depth of the hole. In the upper right corner, an isometric perspective provides a three-dimensional view of the object, displaying the front face with the hole and sides extending back, labeled "TOP," "FRONT," and "SIDE."

 

Geometric shape with section removed. The image is an engineering drawing showcasing the orthographic projection of a three-dimensional object with a rectangular cutout. It includes three views: top, front, and side, all aligned with a labeled isometric view for reference. The top view shows a rectangle with a dashed line representing the cutout, indicating a hollow section. The front view displays a larger square with a similar dashed line marking the cut, providing a frontal perspective of the recessed area. The side view is a narrow rectangle with a dashed line showing the section's depth. The isometric view combines these perspectives, showing a three-dimensional block with a recessed rectangular cutout. The labels "TOP," "FRONT," and "SIDE" indicate the respective orientations of the views.

 

The hidden lines in this example are there because a part of one corner of the front surface was cut away, or “recessed.

Hidden Surfaces

Directions: Draw the hidden lines which are missing in the views below. Each problem has one incomplete view.

Geometric shapes with the 3 orthographic views. The image is divided into four quadrants, each containing sets of geometric shapes. The shapes are primarily rectangular prisms and right angles, resembling blocks used in spatial reasoning or construction puzzles. Each quadrant holds three to four arrangements of these shapes, drawn in simple line art. In the top left quadrant, there are three shapes: a U-shaped block, an L-shaped block, and three rectangular prisms of varying lengths. The top right quadrant features an arrangement of vertical, stacked rectangles, with some rectangular prisms adjacent to them. The bottom left quadrant displays an L-shaped block, a three-part segmented block, and a simple 90-degree block. Finally, the bottom right quadrant has a stepped-block configuration, a long rectangular prism with a dashed line, and a small, simple step-like block. Each shape is distinct, focusing on three-dimensional form representation in two-dimensional space.

Curved Surfaces

Curved surfaces are perhaps tricky to “see” until you remember that the curve is only shown in one view. You must put the curve in the other views yourself, through visualization. Try to think that when there is a sharp change of direction like at a corner, then that will produce a line visible in another view.  When the change of direction is smooth like a curve, no line will be seen.

Isometric object and the 3 orthographic views needed with curved surfaces. The image displays a technical drawing of a mechanical part, shown in three different views: top, front, and isometric. The part appears to be an L-shaped bracket with a cylindrical hole near the corner of the L. The top view shows the rectangular outline of the part, indicating the position of the hole near one end. The front view shows the L-shape with the cylindrical hole marked. The isometric view presents a three-dimensional perspective, highlighting the curved section of the bracket and the hole, which is visible as a circular cutout on the vertical side.

 

 

Here’s another example of curved surfaces:

Isometric part with curved surfaces and the 3 orthographic views. The image features a technical drawing of an L-shaped bracket from multiple perspectives. In the top right, there is an isometric view showing the bracket with two vertical walls and a flat base. The base has four equally spaced, circular holes. The front view, located at the bottom left, displays a vertical wall with a concave cutout. The right side view is directly to the right of the front view, illustrating the vertical wall of the bracket. Lastly, the top view is shown at the top left corner, depicting the arrangement of four holes on the base in a square pattern.

 

Curved surfaces exercise.

 

Directions: Draw the lines which are missing in the views below. Each problem has one incomplete view. Do not draw center lines.

Isometric and Orthographic views of 4 parts that the student needs to complete what is missing. The image is divided into four quadrants, each containing two-dimensional technical drawings of various mechanical components. The lines are clean and uniform, depicting the shapes precisely without any shading or color variations. Top Left Quadrant: Features a straight cylindrical shape, a curved bracket, a U-shaped channel, and a small rectangular block. Top Right Quadrant: Contains a long rectangular bar, a piece with a distinctive hook-like extension, and a smaller rectangular piece with vertical lines. Bottom Left Quadrant: Displays a shape with a semicircular cutout and a hole, a flat rectangular piece with vertical lines, and a rectangular piece with a single hole. Bottom Right Quadrant: Includes a component with a large cutout similar to a square bracket, a rectangular block, and a piece with a curved line intersecting a square.

Inclined Surfaces

Inclined surfaces are those which are at an angle, or slanted. In other words, they are surfaces which are neither horizontal nor vertical. In viewing orthographic drawings you need to be alert to angles and inclined surfaces, for they are often found on the prints you will be reading later.

Notice the hidden line in the right view created by the inclined surface on this object:

Isometric part and the accompanying orthographic views. The image shows a geometric shape displayed from different angles. In the upper left corner, there is a horizontal rectangle divided into three equal squares. Below it, there is a larger shape resembling an irregular quadrilateral, with one edge extended at an angle. To the right, an upright rectangle is shown, divided in half by a dashed line across its width. The largest shape, found in the upper right corner, appears to be a 3D object resembling a ramp or wedge. It has a rectangular base and sides that gradually incline towards a narrow top.

 

Here is an object with two inclined surfaces.

Isometric part with 3 orthographic views. The image features a technical drawing of a geometric shape, depicted in three different views. On the left, there is a top view showing a rectangle with a smaller rectangle inside it, aligned along the top. Beneath it is a front view displaying a trapezoidal shape extending from the top of the rectangle. Next to these is a side view, represented as a simple rectangle with a dashed line down the center, indicating a hidden feature. On the right, there is an isometric view of the shape, showing it as a three-dimensional rectangular prism with an internal V-shape extending diagonally from top to bottom, aligned with the trapezoid in the front view.

 

Inclined surfaces exercise

Directions: Draw the lines which are missing in the views below. Each problem has one incomplete view.

Isometric and orthographic views of 4 parts. The image is divided into four quadrants, each containing a variety of simple geometric shapes in black outlines on a white background. In the top-left quadrant, there is a horizontal rectangle at the top, followed by a shape resembling a trapezoidal prism. Beneath them is a shape resembling a house with a triangular roof, and a vertical rectangle to its right. In the top-right quadrant, a long horizontal rectangle is placed above an envelope shape composed of a rectangle with a diagonal line from the bottom corners meeting at a point halfway up the rectangle. To its right is a narrow vertical rectangle with a horizontal line dividing it. The bottom-left quadrant contains a large horizontal rectangle with a diagonal line from the top left corner to the bottom edge, next to a smaller square. In the bottom-right quadrant, there's a square with a diagonal line across it, a step-like shape composed of three square-like segments, and a vertical rectangle with a horizontal line dividing it near the top.

 

License

Icon for the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

Blueprint Reading For CAD I Copyright © by SBCCOE is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book