Orthographic Projection

TODAY’S OBJECTIVE… Introduce the basic principles of orthographic projection Construct an orthographic Multiview of a simple object Visualize 3-D objects from multiview orthographic drawings

TWO TYPES OF DRAWINGS Orthographic Pictorial Multiview Axonometric Six Principle Views Section Full Half Offset Partial Revolved Auxiliary Primary Secondary Pictorial Axonometric Isometric Dimetric Trimetric Oblique Cavalier Cabinet Others Perspective One Point Two Point Three Point

IT IS A 3-D WORLD The three dimensions are Height Width Depth Pairing the dimensions with one another creates three planes used in orthographic projection Profile Plane = Height + Width Horizontal Plane = Width + Depth Vertical Plane = Height + Depth

ANGLES OF PROJECTION First Angle Third Angle Projection Plane is placed on the other side of object from viewer Object is placed in the first quadrant Primarily used in Europe and Asia Third Angle Projection Plane is placed between the object and the viewer Object is placed in the third quadrant Primarily used the United States

ORTHOGRAPHIC PROJECTION Ortho – Greek word meaning perpendicular Orthographic literally means perpendicular view To look straight at an objects hides a dimension Show the views of a 3-D object projected in 2-D Most common is the front top and side views

MULTIVIEWS (third angle of projection) Picture an object in the center of a glass cube Project the surfaces onto the faces of the glass cube

Multiviews: Unfold the cube so that it lies in a single plane Multiple views of the object are now visible on the same plane in space

There are SIX PRINCIPLE VIEWS Front, Top, Right, Left, Bottom & Back In this class we know which view we are looking at by it’s relationship to the front side view – NEVER LABEL YOUR VIEWS in this class!

There are SIX PRINCIPLE VIEWS Although there are six principle views you only need to draw the ones that are necessary to define the object It is common to show three principle views in this class, front, top & side

MULTIVIEWS: FRONT VIEW: Height and Width (Profile Plane) When the glass cube is unfolded: FRONT VIEW: Height and Width (Profile Plane) TOP VIEW: Width and Depth (Horizontal Plane) RIGHT SIDE VIEW: Depth and Height (Vertical Plane)

MULTIVIEWS: Align views with each other (features project from one view to the next)

POINTS, LINES & SURFACES Point – a location in space - often the intersection of at least two object lines When projecting a point to the adjacent view, it is always on a straight line parallel to the plane of projection Such that when projecting a point from the front side view to the top side view it would be directly above it

POINTS, LINES & SURFACES (Object) Lines – represent the intersection of two surfaces & are projected by using their endpoints Four Types of object lines (three are straight) Normal – (Horizontal & Vertical) appear true length on two planes of projection and as a point in the third Inclined – parallel to one plane of projection (true size) an inclined to the other two (foreshortened) Oblique – not parallel, not perpendicular to any plane of projection (foreshortened in all three planes of projection) Curved (not straight) – only circles and arcs of circles can be projected using its endpoints

POINTS, LINES & SURFACES Four types of surfaces Normal – Given three views, a normal surface will appear true in size & shape in one and as an edge in the other two Inclined –will appear foreshortened in two views & the edge view will be neither horizontal or vertical Oblique – will appear foreshortened in all three view Curved – Cylinders appear as a circle in one view and as rectangle in the adjacent view This lesson will focus on normal surfaces

MULTIVIUEWS: NORMAL SURFACES Parallel to one of the three planes of projection in which it appears true in size & shape Later we will even work with rounded surfaces!

MULTIVIUEWS: NORMAL SURFACES Parallel to one of the three planes or two panes of glass in our transparent cube Show true size and shape in the view they are parallel to Shown as edges in other principle views

MULTIVIUEWS: LINE TYPES When two surfaces meet it creates a line (edge) When that edge is visible we use an object line (a clear, crisp & dark solid line) When that edge is behind a surface (not visible) we use a hidden line (a clear, crisp & dark dashed line) When a hidden line is directly behind an object line the object line takes precedent

Selecting the Front Side View Is the front of the car shown in the front side view? Why or why not? Profile View Best view that shows shape or contour Most details Fewest hidden lines Natural or functioning position Principle Surface area parallel to plane of projection Minimize depth

Select an appropriate front side view and begin to hand sketch a multiview (Front, Top, side) of this part now. Do not worry about scale but do your best to project (align) points, lines and surfaces to the adjacent views .