Engineering Graphics: Pictorials, Projections, and Orthographic Views

Comprehensive vocabulary flashcards covering engineering projections, pictorial drawings (isometric and oblique), sketching procedures, CAD constraints, orthographic views, line types, and line precedence.

Pictorials

Pseudo $3\text{D}$ drawings that are drawn in $2\text{D}$ but look $3\text{D}$.

Line of Sight

An imaginary ray of light between an observer's eye and an object, which can be parallel or converge.

Plane of Projection

An imaginary flat plane upon which the image created by the line of sight is projected.

View

An image on a projection plane that depends on the relative orientation between an object and a plane.

Multiview Drawing

A drawing that shows a $2\text{D}$ view of an object.

Axonometric Drawing

A drawing that shows a virtual $3\text{D}$ view of an object.

Isometric Pictorials

Drawings constructed on an isometric axis using full scale that provide a quick method of examining tentative design details and illustrating assemblies.

Regular Isometric

An isometric orientation formed by looking down on the top of the object.

Reverse Axis Isometric

An isometric orientation formed by looking up on the bottom of the object.

Long Axis Isometric

An isometric orientation formed by looking from the right (or left) of the object.

Isometric Hidden Line Rule

The rule that hidden lines are omitted in isometric sketching unless absolutely necessary to completely describe the object.

Isometric Scale Rule

Linear features on or parallel to the three axes are drawn at $80\%$ of full scale to represent true size, though any scale may be used as long as it is uniform on all axes.

Isometric Ellipse Alignment

Circles appear as ellipses whose major axis is aligned with the long diagonal of a defining box, touching the box at the midpoint of its sides.

Oblique Pictorials

Pictorial drawings where only one axis is positioned at an angle between $0^\circ$ and $90^\circ$.

Angled Axis (Oblique)

The axis in oblique pictorials where features may be drawn full scale, foreshortened, or half scale (most common).

Topology Optimization

A technique for optimum material distribution in a given design domain that refers to "digging holes" in the domain.

Constraints

Rules applied to sketches in order to fix the design.

Fully Constrained

The condition where a sketch design is completely fixed, represented visually by turning from a blue to a black sketch.

Geometric Constraints

Rules that define specific points on geometric objects and determine their orientations to other objects.

Dimensional Constraints

Rules that determine the distance and size of a design.

Glass Box Method

A method where an object is imagined in the center of a transparent box, and different views are projected onto its $6$ sides (or $6$ principle planes) as mirror images with different line types.

Standard Views

A subset of principle views necessary to describe the shape of an object, consisting of TOP, FRONT, and RIGHT views.

View Alignment

The standard layout rule where the TOP and FRONT views align vertically and share width, while FRONT and RIGHT side views align horizontally and share height.

Visible Line

A solid, thick line used for visible edges and boundaries.

Center Line

A thin line with alternating long lines and short dashes used for axes of symmetry (only for circles, not arcs), circle of centers, and paths of motion.

Hidden Line

A medium thick dashed line used for edges and boundaries that cannot be seen.

Phantom Line

A thin line used for indicating alternate positions of moving parts, adjacent positions of related parts, or repeated detail.

Cutting Plane Line

A very thick line with arrows indicating the direction of sight, used for showing an imaginary cut to view interior features.

Section Lines

Thin parallel lines ($/////$) used for showing areas that have been cut by the cutting plane.

Break Line

A line type used for showing imaginary breaks.

Line Precedence

The order of importance when two lines overlap (omitting the less important): 1. Cutting Plane line, 2. Visible line, 3. Hidden line, 4. Phantom line, 5. Center line.

Perspective Projection

A projection where the observer is at a finite distance and rays/projectors converge at the observer's eye, which does not provide exact size and shape.

Orthographic Projection

A projection where the observer is assumed to be at infinite distance and rays/projection lines are parallel to each other and perpendicular to the plane of projection.

Oblique Projection

A projection where the observer is at infinite distance and rays/projection lines are parallel to each other but not perpendicular to the plane of projection.

Isometric Projection

A projection where the observer is at infinite distance, rays/projection lines are parallel to each other and perpendicular to the plane of projection, and all faces of the object are equally inclined to the planes of projection.