Chapter 3: Orthographic Projection
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Questions and Answers

What happens to a circular hole in perspective drawing?

  • It turns into a square
  • It remains circular
  • It becomes an ellipse (correct)
  • It disappears entirely

    • A right angle in perspective drawing can appear as an obtuse angle.

    True

    What are the three dimensions considered in multiview drawing?

    Height, Width, Depth

    In multiview drawing, the observer can either revolute the object or __________ around it.

    <p>move</p> Signup and view all the answers

    Match each view of the object with its corresponding position:

    <p>Top view = View from above Front view = View from the front Right side view = View from the right side Rear view = View from the back</p> Signup and view all the answers

    Which drawing technique requires understanding the relative orientation of views?

    <p>Multiview drawing</p> Signup and view all the answers

    The depth of an object is irrelevant in multiview drawing.

    <p>False</p> Signup and view all the answers

    What is the glass box concept in relation to drawing methods?

    <p>It allows for the visualization of the object from multiple angles.</p> Signup and view all the answers

    What shape should the intersection between hidden lines form?

    <p>L, T, V, or Y corner</p> Signup and view all the answers

    A center line should always start and end with a short dash.

    <p>False</p> Signup and view all the answers

    What type of line denotes a visible line in the drawings?

    <p>V</p> Signup and view all the answers

    The hidden line should join a visible line, except it extends from a visible line ______.

    <p>space</p> Signup and view all the answers

    In a circular view, where should the short dash of a center line cross?

    <p>At the center of the circle or arc</p> Signup and view all the answers

    Match the line types with their descriptions:

    <p>Visible line = Denoted by 'V' Hidden line = Denoted by 'H' Center line = Denoted by 'C' Dashed line = Used to represent a space or connection</p> Signup and view all the answers

    For small holes, the center line is presented as a thin continuous line.

    <p>True</p> Signup and view all the answers

    What is the minimum gap that should be left when a center line forms a continuation with a visible or a hidden line?

    <p>3~4 mm</p> Signup and view all the answers

    In a multiview drawing, what happens in the case of intersection?

    <p>An edge becomes a line</p> Signup and view all the answers

    In a multiview drawing, a tangential relationship indicates that an edge and a line exist.

    <p>False</p> Signup and view all the answers

    What are the three types of planes mentioned?

    <p>Normal plane, Inclined plane, Curve surface</p> Signup and view all the answers

    When lines coincide in a drawing, the most important line is a _____ line.

    <p>visible</p> Signup and view all the answers

    Match the following line types with their descriptions.

    <p>Visible line = Represents an edge that can be seen Hidden line = Represents edges that are not visible Center line = Indicates the center of circles or symmetrical objects Construction line = Used as guidelines for drawing other lines</p> Signup and view all the answers

    What is the order of precedence for lines in multiview drawings?

    <p>Visible line, Hidden line, Center line</p> Signup and view all the answers

    Modifying an object's features has no effect on its multiview drawing.

    <p>False</p> Signup and view all the answers

    What should you attempt when relating object features to lines in a multiview drawing?

    <p>Interpret the meaning of lines</p> Signup and view all the answers

    What concept helps in visualizing the projection of an inclined plane?

    <p>Glass box concept</p> Signup and view all the answers

    An obliqued line maintains its angle during projection.

    <p>False</p> Signup and view all the answers

    What is the purpose of transferring a depth in drawing?

    <p>To ensure accurate representation of three-dimensional measurements.</p> Signup and view all the answers

    The projection of a ______ surface can either tangent or intersect with an adjacent plane.

    <p>curved</p> Signup and view all the answers

    Match the type of projection to its correct description:

    <p>Inclined line = Projects at an angle and is not vertical or horizontal Curved line = Representation of a line that bends between two points Obliqued line = Projects at a slant across the view plane Miter line = Used for transferring angles and creating connections between views</p> Signup and view all the answers

    Which of the following best describes a miter line?

    <p>A line used to create connections between front and side views</p> Signup and view all the answers

    In projection drawings, it's essential to provide space between front and side views.

    <p>True</p> Signup and view all the answers

    What do the letters 'BT', 'AT', and 'BR' typically denote in projection drawings?

    <p>They represent different view orientations or reference points.</p> Signup and view all the answers

    Which of the following shapes has no edges?

    <p>Sphere</p> Signup and view all the answers

    All surfaces can only be plane and cannot be curved.

    <p>False</p> Signup and view all the answers

    What is used in multiview drawing to indicate the existence of a hidden edge?

    <p>Hidden line</p> Signup and view all the answers

    A surface is defined as an area that is bounded by edges or _______.

    <p>surface limit</p> Signup and view all the answers

    Match the following shapes with their characteristics:

    <p>Prism = Has flat surfaces and straight edges Cylinder = Has one curved surface and two flat surfaces Sphere = Is perfectly round with no edges Cone = Has one curved surface and one flat surface</p> Signup and view all the answers

    What is the primary purpose of projection theory in orthographic projection?

    <p>To graphically represent a 3-D object on 2-D media</p> Signup and view all the answers

    Orthographic projection includes both parallel and oblique lines of sight.

    <p>False</p> Signup and view all the answers

    What type of drawing shows a virtual 3D view of an object?

    <p>Axonometric drawing</p> Signup and view all the answers

    The _____ projection uses parallel lines of sight.

    <p>orthographic</p> Signup and view all the answers

    Which of the following are types of projections mentioned in the content?

    <p>Multiview and Axonometric</p> Signup and view all the answers

    Match each type of projection with its characteristic:

    <p>Multiview drawing = Accurate representation of object details Pictorial drawing = Easy to visualize but less accurate Perspective drawing = Creates depth in visual representation Orthographic projection = Uses parallel lines of sight</p> Signup and view all the answers

    A disadvantage of multiview drawing is that it requires training to visualize.

    <p>True</p> Signup and view all the answers

    What are the two primary variables that projection theory is based on?

    <p>Line of sight and plane of projection</p> Signup and view all the answers

    What is the function of a rib and web in structural design?

    <p>Act as structural supports</p> Signup and view all the answers

    A spoke is the rod that connects the hub to the rim of a wheel.

    <p>True</p> Signup and view all the answers

    What is the definition of a lug in mechanical terms?

    <p>A lug is an ear or extension built as part of an object for attachment.</p> Signup and view all the answers

    In section view representation, omit the section lines on the section view of ______, ______, and ______ if the cutting plane is passed flatwise through.

    <p>rib, web, lug</p> Signup and view all the answers

    Match the following terms with their corresponding descriptions:

    <p>Rib = Thin, flat structural support Web = Flat feature for support Spoke = Rod from hub to rim of wheel Lug = Extension for attachment</p> Signup and view all the answers

    What is an aligned section?

    <p>A section drawn by rotating features about symmetry axis</p> Signup and view all the answers

    Conventional breaks are used to display long objects in a small scale by removing unimportant long portions.

    <p>True</p> Signup and view all the answers

    What is the recommended practice when cutting through a spoke?

    <p>Omit section lines if the cutting plane is passed longwise through.</p> Signup and view all the answers

    Study Notes

    Chapter 3: Orthographic Projection

    • This chapter covers orthographic projection, a method of representing three-dimensional (3D) objects on two-dimensional (2D) media.
    • Orthographic projection uses parallel projection lines, normal (orthogonal) to the projection plane.

    Contents

    • Projection theory
    • Multiview drawing
    • Line convention

    Purpose of Orthographic Projection

    • To graphically represent 3D objects on 2D media (e.g., paper, screen).
    • This method makes object features transferable for communication, overcoming the inconvenience of communicating 3D objects directly.

    Concept of Orthographic Projection

    • Based on two variables:
      • Line of sight (LOS): An imaginary ray of light between the observer's eye and the object.
      • Plane of projection: An imaginary flat plane upon which the image created by the LOS is projected.

    Types of Lines of Sight

    • Parallel projection: Projection lines are parallel.
    • Converge projection: Projection lines converge at a vanishing point.

    Line of Sight (LOS) in Orthographic Projection

    • The projection lines in orthographic projection are parallel and normal (orthogonal) to the plane of projection.

    Orthographic Projection

    • In this course, only parallel and orthogonal projections (i.e., orthographic projection) are considered.
    • Oblique projection is not covered.

    View Types

    • Image on a projection plane.
    • View depends on the relative orientation between an object and a plane.
      • Multiview drawing: Shows a 2D view of an object.
      • Axonometric drawing: Shows a virtual 3D view of the object.

    Summary of View Types

    • The type of views and projections cover aspects of various types: parallel and converge projections, orthogonal, oblique views - including multiview, pictorial, and perspective drawings.

    View Comparison

    • Multiview drawing:
      • Advantage: Accurately depicts object details (size and shape).
      • Disadvantage: Requires training for visualization.
    • Pictorial drawing:
      • Advantage: Easy to visualize.
      • Disadvantage: Can lead to shape and angle distortion.
    • Perspective drawing:
      • Advantage: Object representation resembles how our eyes perceive it.
      • Disadvantage: Difficult to create, and often distorts size and shape.

    Definition of Multiview Drawing

    • A set of related images created by viewing the object from different directions.
    • Adjacent views are needed to provide a complete object description. (Height, Width, Depth).

    Methods for Creating Multiview Drawings

    • Revolve the object with respect to the observer.
    • The observer moves around the object.
    • Glass box concept: Revolution of the planes of projection (Top view, Front view, Right side view, Rear view, Left side view, Bottom view).

    Relative Orientation of Views

    • Demonstrates the relationships between different views. (Top view, Front view, Rear view, Left side view, Right side view, Bottom view).

    Problem Solving Steps in Multiview Drawing

    • Given a 3D representation of an object:
      • Identify the features
      • Match the identified features with the lines (or areas) in the views.
      • Establish line (or plane) types (normal, inclined, oblique)

    Object Features in Multiview Drawing

    • Edge: Represents the boundary between two faces.
    • Surface Limit: Represents the last visible part of the curved surface.
    • Surface: Defined area bounded by edges or surface limits (can be plane or curve).

    Projection of Lines, Planes, and Curved Features in Multiview Drawings

    • Normal lines
    • Inclined lines
    • Oblique lines, planes and curved objects (including cases of intersection and tangency with adjacent surfaces).

    Transferring Depth in Multiview Drawings

    • Direct measurement: Use a ruler.
    • Miter line: 45-degree line for accurate depth transfer (and precise depth measurement transfer).

    Projection of an Object with Curved Surfaces

    • Curved surface can be tangent or intersect adjacent planes.
    • In intersection, edge becomes a line in the multiview.
    • Tangential case: no edge or line in multiview.

    Examples of Multiview Drawings

    • A variety of objects and their corresponding multiview drawings are given, demonstrating practical applications.

    Further Practice

    • Suggestions for practicing multiview drawing - Interpretation of lines; Modifying the object and observing changes in the drawing

    Types of Planes

    • Normal
    • Inclined
    • Curved surface

    Line Conventions

    • Precedence of coincide lines
    • Hidden line drawing
    • Center line drawing

    Hidden Line Drawings

    • Rules for drawing hidden lines, to show their existence.
    • Intersection between hidden lines (forming L, T, V, or Y corners).
    • Curve hidden lines starting on center lines.  (Detailed applications and examples provided).

    Center Line Drawings

    • Must start and end with a long dash.
    • In circular views, short dashes should cross the center of the circle/arc.
    • Center lines should not extend between views.
    • For small holes, a center line is presented as a thin continuous line.
    • Gap when a centerline continues with a visible or hidden line. (Specific examples provided for appropriate application.)

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    Related Documents

    Chapter 3 Orthographic Projection PDF
    Chapter 4 Conventional Practice in Section View PDF

    Description

    This quiz covers orthographic projection, a crucial method for representing 3D objects in 2D formats. Test your knowledge on the principles of projection theory, multiview drawing, and line conventions as they apply to this essential graphic representation technique.

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