Lecture 3: Projections

Question 1

Projection variables (2)

Answer 1

Line of sight and plane of projection

Question 2

Line of sight

Answer 2

Imaginary line between an observer’s eye and an object

Question 3

Plane of projection

Answer 3

Imaginary flat plane where an image is projected

Question 4

2D projection

Answer 4

Created by connecting the points where the line of sight pierces the projection plane

Question 5

Types of projection (2)

Answer 5

Perspective and parallel

Question 6

Perspective projection

Answer 6

Lines of sight are not parallel and converge at a point. The further away form an object the viewpoint is, the more the projection angle decreases.

Question 7

Parallel perspective

Answer 7

Lines of sight are parallel to each other and go an infinite distance/do not converge.

Question 8

1 point perspective

Answer 8

View plane is parallel to a plane of the object, with the lines perpendicular to the view plane appear to converge at the vanishing point.

Question 9

2 point perspective

Answer 9

Horizontal lines appear to recede at 2 vanishing points at either end of the projection image. Vertical lines are parallel to each other.

Question 10

3 point perspective

Answer 10

Horizontal lines appear to recede at the 1st and 2nd vanishing points. Vertical lines are not parallel and recede at the third vanishing point.

Question 11

Atmospheric/aerial perspective

Answer 11

Lines become less clear and less detailed the farther away the object is. Colors are more bluish in hue and muted.

Question 12

Oblique projection

Answer 12

Parallel projection in which the lines of sight are not perpendicular to the projection plane. X (width) and Z (height) axes are drawn at full scale while the Y (depth) axis is drawn at an angle to the horizontal and may have a different scale or be foreshortened.

Question 13

Cavalier oblique projection

Answer 13

The depth axis is drawn full scale

Question 14

Cabinet oblique projection

Answer 14

The depth is drawn half scale

Question 15

Orthographic projection

Answer 15

All the lines of sight are perpendicular to the projection plane, resulting in every plane of the object being visible. Different projection types are made by orienting the object differently relative to the projection plane.

Question 16

Types of orthographic projections (2)

Answer 16

Axonometric and multi-view

Question 17

Axonometric orthographic projection

Answer 17

One corner of the object is oriented towards the observer.

Question 18

Types of axonometric projections (3)

Answer 18

1. Isometric: 120°/120°/120°
2. Dimetric: 150°/105°/105°
3. Trimetric: 120°/105°/135°
   *these angles are between the axes’ projections and not the true angles between the axes.

Question 19

Multi-view orthographic projection

Answer 19

One object face is parallel to the projection plane, with 6 standard projection planes. (top, bottom, front, back/rear, left, right)

Question 20

Visible lines

Answer 20

Solid and highest weight, for visible lines and boundaries

Question 21

Hidden lines

Answer 21

Dashed, for edges and boundaries that can’t be seen

Question 22

Center lines

Answer 22

Dots and dashes, for the center of circles, axes, symmetry planes, etc…

Question 23

Construction lines

Answer 23

Solid and the lowest weight, for creating objects

Question 24

Which side is the front of an object?

Answer 24

Side with the most features of the object and the least number of hidden lines