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 (A)

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 (A)</p> Signup and view all the answers

The depth of an object is irrelevant in multiview drawing.

<p>False (B)</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 (C)</p> Signup and view all the answers

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

<p>False (B)</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 (A)</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 (A)</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 (B)</p> Signup and view all the answers

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

<p>False (B)</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 (B)</p> Signup and view all the answers

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

<p>False (B)</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 (A)</p> Signup and view all the answers

An obliqued line maintains its angle during projection.

<p>False (B)</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 (D)</p> Signup and view all the answers

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

<p>True (A)</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 (C)</p> Signup and view all the answers

All surfaces can only be plane and cannot be curved.

<p>False (B)</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 (B)</p> Signup and view all the answers

Orthographic projection includes both parallel and oblique lines of sight.

<p>False (B)</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 (C)</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 (A)</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 (A)</p> Signup and view all the answers

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

<p>True (A)</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 (A)</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 (A)</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

Flashcards

Edge

A boundary line where two surfaces meet. Think of it as the sharp edge of a box or the seam between two pieces of paper.

Surface

The flat or curved area that makes up the outside of an object. Imagine the smooth face of a cube or the curved exterior of a ball.

Surface limit

A line marking the end of a surface. It's like the border of your drawing.

Normal Line

A line that is perpendicular to a plane and represents the direction an object is facing.

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Normal Plane

A flat surface that is perpendicular to a line of sight. Think of it as a transparent wall.

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Multiview drawing

A type of drawing where an object is viewed from multiple directions, creating related images that show its complete form.

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Projection line

The line that represents the intersection of a plane of projection and the object.

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Depth in Multiview drawing

A visual representation of an object's height, width, and depth, where depth is shown by angles and perspectives.

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Moving observer method

A method of creating multiview drawings by moving the observer around a stationary object.

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Revolving object method

A method of creating multiview drawings by rotating the object while the observer remains in a fixed position.

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Orthographic Projection

A method to represent a 3D object on a 2D surface like paper or screen.

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Line of Sight (LOS)

An imaginary line extending from the observer's eye to a point on the object.

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Plane of Projection

An imaginary flat surface where the image created by the Line of Sight is projected.

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Orthogonal Projection

A type of projection where the lines of sight are parallel to each other and perpendicular to the plane of projection.

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Oblique Projection

A type of projection where the lines of sight are parallel to each other but not perpendicular to the plane of projection.

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Axonometric Drawing

A drawing that shows a 3D view of an object, typically using perspective techniques to create a sense of depth.

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Perspective Drawing

A type of drawing that utilizes perspective techniques to create a realistic representation of a 3D object.

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Inclined Line

A line that is not parallel or perpendicular to the projection planes.

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Inclined Plane

A plane (flat surface) that is not parallel or perpendicular to the projection planes.

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Obliqued Line

A line that intersects the projection planes at an oblique angle.

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Obliqued Plane

A plane that intersects the projection planes at an oblique angle.

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Curve Line

A line made of curves.

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Curve Surface

A surface made of curves.

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Direct Measurement (Depth Transfer)

A method of transferring depth information from a side view to a front view directly using measurements.

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Miter Line (Depth Transfer)

A line drawn at a 45-degree angle to transfer depth information from one view to another.

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Hidden Line

A line representing an edge that is not visible from the current viewpoint.

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Center Line

A line that starts and ends with a long dash, used to indicate the center of an object or feature.

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Visible Line

A line that represents an edge that can be seen from the current viewpoint.

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Hidden Line Corner

An intersection between hidden lines that creates a corner resembling the letter L, T, V, or Y.

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Curved Hidden Line

A hidden line that starts on a center line and represents an edge that cannot be seen from the current viewpoint.

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Small Hole Center Line

A representation of a small hole, depicted as a single thin line.

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Center Line Extension

A center line should not extend between views.

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Center Line Gap

There should be a gap between center lines and visible or hidden lines.

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Intersection Line

A type of line used in multiview drawings to indicate the boundary between two surfaces, forming a visible edge on the object.

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Dashed Line

A type of line used in multiview drawings to represent an edge that is obscured from view by another surface. It is indicated by a series of short dashes or dots.

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Construction Line

A line used in multiview drawings to indicate features that are not part of the final object. It is typically represented by a thin, light line.

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Edge Line

A line in a multiview drawing signifies an edge when two surfaces meet. If not visible from the viewpoint, it's presented as a dashed line.

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Precedence of Lines

When drawing lines that coincide, the most relevant line takes precedence, covering up the others. The order of importance is visible, hidden, center, then construction lines.

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Rib and Web

A thin, flat feature of an object, acting as structural support.

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Spoke

A rod radiating from the hub to the rim of a wheel.

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Aligned Section

A section view obtained by rotating the object's features around a symmetry axis, showing them in a principal view.

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Conventional Break

A technique for representing long objects in drawings by removing a portion and indicating the break with lines.

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Convention for Section Lines

Omitting section lines in a section view, particularly when the cutting plane passes flatwise through certain features.

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Misleading Impression of Spoke

Misleading impression can occur using a normal section view of a spoke. It leads to an incorrect interpretation of the spoke's shape.

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Multiple Section View

When displaying multiple section views you should show the object at its true shape.

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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

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