Visual Communication terminology and theory.

Projection

Process of reproducing a spatial object onto a plane. Done by projecting points

Which of the following are the elements planar projection?

• 3D object or scene is projected

• Line of sight (LOS)

• 2D projection plane

• Projected 2D image formed on projection plane

Line of sight (LOS)

An imaginary ray of light between the observers eye and the object

2D projection plane

An imaginary flat plane where the images lines of sight are projected

Perspective Projection

• Mimics what the human eye sees.

• Works by converging to a single viewpoint.

• Distance changes size of projection

• Not very useful in engineering application because it doesn’t show the true size.

Center of projection (CP)

Represents position of the observer in perspective projection. It’s a finite distance from the object

Parallel Projection

• Plane of projection is always parallel to the object

• It’s useful for ability to do realistic depiction of an object and show the true size

Pictorial projection

A type of projection which includes all three dimensions, hence creating an illusion of depth.

Multiview projection

Presents an object in a series of projections which only show two of an object’s dimensions

Orthographic projection

• A parallel projection technique where the plane of projection is between the observer and the object.

• The object is perpendicular to the lines of site

• lines of site are parallel

Oblique Projection

Parallel projectors intersect a projection plane at an oblique angle. One principle face of the object will be parallel to the projection plane

Features of Oblique projection

• More focus on the front side of an object or face

• Combines the ease of sketching in two dimension with a need to represent the third

• Useful when majority of features are on the front face of an object

Engineering design

Process of devising a system, component, or process to meet desired needs and specifications within constraints.

It’s and interactive, creative, decision-making process which uses basic sciences, mathematics, and engineering sciences to apply when in converting resources into solutions

Wicked problems

ill-formulated problems with confusing information.

Can be many clients and decision makers with conflicting values so ramifications in the whole system is confusing

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Axonometric projection

When orthographic projections are subdivided based on orientations of the object with respect to the projection plane.

All principal axes are inclined.

Classifications of Axonometric Projection

• Trimetric: No angles between principle axes are equal

• Dimetric: 2 angles between principle axes are equal

• Isometric: All angles between principle axes are equal

What is the difference between Isometric and Oblique Projections?

Oblique sketching: The front face of the object is squared with the paper and the depth is drawn at an angle to the horizontal.

Isometric: No faces are squared with the paper

Multiview Drawing

Based on parallel projections. It’s application is to represent features more accurately than a pictorial view can represent.

In general they should minimize views needed to describe object and avoid repetition

Freehand sketching

Sketching without a tool

Partitioning Lines

A technique

Contour Sketch

Created by observing the outline of a object. The technique can improve sketching ability

What is Transfer of Depth

Something done by using a 45 degree miter line to do feature alignment with the two depth sides in a Multiview drawing

What are the line conventions?

• Visible line

• Hidden line

• Center line

• Dimension & Extension lines

• Section lines

Applications of visible lines:

• Edge view of a surface

• Edge between two intersecting surfaces

• Extent of a contoured surface

Limiting element

A line that represents the furthest outside of a feature in a curved surface. It is not the boundary between faces. This line is tangent to the curved edge at each end of a cylinder

What are hidden lines used for?

They represent:

• a hidden edge of a surface

• a hidden change of planes

• the hidden extents or limiting extents of a hole

What are center lines used for

To represent the axis of a cylinder or hole.

Note that a circular view would use crossing centerlines

What is the line precedence?

Visible line takes priority over hidden line. Hidden line takes priority over center line

What decisions much be made to determine the best views?

• Best position of the object

• Front show should show object in its natural, assembled state and be most descriptive

• A minimum number of views should be chosen to completely describe the object

How do you create a Three-View Sketch?

• Use light construction line to create properly proportions bounding box views

• add front view details

• project further details from front views to adjacent views

• then go bold starting with curved features

What is foreshortening?

When features get foreshortened due to lines of sight not being perpendicular to a feature

Fundamental Views

^{True size is shown. This happens when parallel to the plane of projection, hence making it perpendicular to the line of sight. Also is true length when perpendicular to the plane of projection}

Normal line

Also known are true-length line. Is parallel to the plane of projection

Normal Face

Also known as principal plane. Happens when parallel to the plane of projection, causing it to be perpendicular to the line of sight. Therefore, it is true size

Inclined Face

It will be a normal surface when rotated about a line parallel to a principal axis. It will be perpendicular to one principal plane the inclined to other views. They will appear foreshortened

Oblique Face

A planar surface that has been rotated about two principle axes. It will be inclined in all principal projections planes. Therefore, none will show the true size.

What are fillets/rounds? What do they do?

They connect two object with a tangent arc in 2D and create a round transition between adjacent faces of a 3D solid

Fillets: Inside corner

Round: outside corner

What can happen when drawing fillets or rounds

They can be ignored and still drawn as edges despite being theoretically not being drawing since there’s no change in plane

Intersections and Tangency

When plane surfaces intersects with a curved surface, a line can be drawn with respect to intersecting surfaces

When tangent, no edge is shown

Third angle projection

Standard in use and Canada when box is drawn from third quadrant.

First angle projection

Standard in Europe and other countries. Object is drawn from the first quadrant

What is visualization?

The process by which a shape information on a drawing is translated so that the viewer can understand the objects’ representation.

It should be possible to create a 3D drawing from a Multiview drawing

What are visualization techniques?

• Study completed Multiviews of completed objects

• Create physical model from clay, wax or Styrofoam

• Decompose complex geometries into simple geometries

• Study or adjacent areas

• similar shaped surfaces

• Surface labeling

• Vortex labeling

• solving missing-line problems

• solving missing view problems

• Sketching well proportions pictorial view of the object

What do adjacent areas represent?

• surfaces are different levels

• inclined or oblique surfaces

• cylindrical surfaces

• combination of the above

Explain the similar shaped surfaces technique

Similar shaped surfaces retain their basic configuration in all views except when viewed on the edge

Explain vortex labeling

In addition to labeling surfaces, vertices of complicated surfaces should be labeled and then projected

What is solving missing-line problems?

Accomplished by identifying edges in one view that don’t appear in an adjacent or related view. When projecting the location of these edges, locations of missing lines can be identified

What is solving missing-view problems?

When trying to find a missing third view, edge features that are provided can be projected to help find the missing view

How do you sketch a well-proportioned pictorial view of an object

First sketch the object’s bounding box, then use given views to identify prominent object features. These features can be added to the pictorial sketch

What is a similarity and a difference between isometric drawing and isometric projection

The same methods is used for drawing both. However isometric drawing has actual dimensions while isometric projection dimensions should be multiplied by 0.8

What is the theory of isonomic projection?

The object gets rotated 45 degrees about the vertical access, then it’s tilted forward until the body diagonal appears as a point in the front views.

Isometric lines

A line parallel to a leg in the isometric axis. True-length distance can be measured along these lines

Isometric Planes

Anything parallel to the cube faces

What are the standards for hidden lines, center lines, and dimensions in isometric drawing.

Hidden lines are typically omitted unless absolutely necessary to describe the object. Center lines are typically not shown since isometric drawings communicate to non-technical people.

What is dimensioning?

The process of adding size information to a drawing.

What is the dimensioning criteria?

• Only use dimensions needed to completely define a part

• Dimensioned part should not be subject to different interpretations

• Don’t specify manufacturing methods that will be used in building a part

• Arrange dimensions for optimum readability

• Dimensions should appear in true profile views and refer to visible object edges

List dimensioning terminology

Group dimensions

Dimensions are grouped in a drawing. Object lines should not be used as extension lines

What is the purpose of section view?

When there’s complex parts containing several internal features. Often that’s apparent when those details show up as hidden lines with Multiview projection.

What are types of section views?

• Full section: completely through and object

• half section: halfway through an object

• offset section: ben to go through features which aren’t aligned

• broken-out section: Go through part of the object

What is an application of auxiliary views

Represent inclined features and show true size for something not normal to observer

Auxiliary view conventions

• hidden lines are typically ommited

• Letters “TS” are added to state it’s undistorted

What is the purpose of displaying results

• communication

• exploration

• storage

• calculation

• decoration

What are two ways of displaying informatoin

Tables: For numerical data and small data sets

Figures: illustrations that aren’t table. They’re for large datasets

Time series

Used to display data sets with real variability

Graphical integrity

When the visual representation of data is consistent with the numerical representation

Misleading figures

Sometimes a graph is presented in a way that is confusing because it’s not in a standard, expected format. An example is making the graph upside-down

Lie factor

A way to describe the amount of distortion in a graph. This is associated with graphical integrity

Design and Data variation. What is appropriate

There should never be more design variation than data variation. The reason is because it can lead to ambiguity and deception

What is the role of context in graphical integrity?

Enables it to be truthful and revealing

Data density

Note that eye can do a lot of distinctions in a small area

Data density = number of entries/area of graph

Data-ink

A ratio of how much data there is to ink.

Ideally the ratio should be maximized to not use redundant ink

Chart Junk

When the interior decoration of graphics doesn’t tell the reader anything new. Often related to low data-ink ratio

Moiré Vibration

Is a form of chart junk which is an optical effect creating a shake-illusion

The Grid

When there’s one or more sedate graphical elements. It should be suppressed so that its presence doesn’t compete with data

Duck

When the decoration dominates data

Self-Promoting graphics

When there’s an additional fake perspective. It’s a form of chart junk

Ideal graphic presentation

• use sans serif typeface

• Have sufficiently large font

• Don’t do all capital letters

• Do light against dark background or vise-versa

• Keep text blocks to only be 2 or less lines

• Lists should only have 2-4 items and listed items should be parallel

• Have a lot of white space

• Limit numbers on a slide