Visualization and Graphics Introduction Drafting, Sketching & Dimensioning

Objectives Understanding graphics as a communication tool Technical sketching Freehand Instrument Computer Projections Orthographic Pictorial Today’s objectives are: Sketching and Isometric Pictorials - At the end of the session, students should be able to: Infer that technical drawings are effective tools for communication of technical ideas Differentiate between multi-view and isometric drawings Develop isometric sketches of tangible objects on isometric grid sheet Just doing a brief overview of first two topics. We will spend most of the time on Introduction to Projections in particular isometric projection.

Visualization Visualization is often used as a mode of communication between engineers Sketches, tables, graphs, computer generated drawings, blueprints are various ways in which engineers communicate via visual mediums

How Would You Describe This? In teams of two, describe using only words How effective is this approach? Instructor: This is an in-class interactive exercise(active learning). Allow students about 5 minutes to discuss with partner and then ask random students to put in words their description. Then ask the class the question shown on the slide.

Three Basic Types of Technical Drawings Freehand sketches Instrument drawings Computer drawings In this class we will focus primarily on Freehand Sketching and Computer Based drawing CAD programs have replaced much of Instrument drawing process. Technical sketches are how engineers “think” and communicate with each other. All the way from napkin session at lunch to formal computer based solid models and flow charts.

Introduction to Projections Present 3-D objects with 2-D media Two Basic Categories Orthographic Pictorial Definitions: Projection: the process or technique of reproducing a spatial (3-D) object upon a plane or curved (2-D) surface Orthographic sketches present the object in a series of projections, each one showing only two of the object’s three dimensions. Pictorial sketches present the object in a single view with all three dimensions represented Discuss the trade-offs in using any type of projection; some are more realistic, some are easier to draw, and some are easier to interpret by non-technical people

Projections: Four Basic Types Note: Isometric is a special case of Axonometric Orthographic Projections Axonometric Course emphasizes on multi-view (orthographic) and isometric (one type of axonometric pictorial) projections only Multiview projections are a collection of 2-D views Pictorials are 3-D Pictorials Oblique Perspective

Types of Axonometrics

Pictorial Drawings Shows an object like you would see in a photograph Give a three dimensional view of a room or structure Three common types Isometric (Axonometric) Oblique Perspective

Pictorial Sketch of Kitchen

Review Questions 1-2

Isometric Drawings The most common pictorials Constructed with the two faces 30 degrees above the horizontal The axes are 120 degrees between each axis Lines that are horizontal are drawn at 30 degrees Vertical lines remain vertical

Isometric Projection CUBE One type of axonometric pictorial (3-D) projection ‘Iso-’ means ‘equal ‘metric projection’ means ‘a projection to a scaled measure’ The three dimensions are not only shown in one view, but also the dimensions can be scaled from this drawing START WITH A CUBE All of the normal drawing planes (top, front, side) are equally foreshortened or tilted, and all of the major axes (X, Y, Z) are at equal rotations from each other (120 degrees apart), as in the illustration above. And, because all of the major planes are equally foreshortened, all of the measurements in these planes are equal as well as shown above. This means that the same measuring scale may be used in drawing both the width, height, and depth of objects. Isometric means equal measure All planes are equally or proportionately shortened and tilted All the major axes (X, Y, Z) are 120 degrees apart

Making an Isometric Sketch Defining Axis 30o 60o Isometric Axis Derive the axes from a vertex of the cube

Isometric of a Cube

Isometric Dimensioning Dimension lines are parallel to the isometric axes Extension lines are extended in line with these axes

Oblique Drawings The front view is draw like it would be using orthographic projection The front view shows all features with true shape and size The top and side view are then projected back from the front view Views can be at any angle 15, 30 or 45 degrees are common

Oblique Drawing

Oblique Drawings Continued Useful when the front contains more details and features than the side view A mental image can be created more quickly than with orthographic alone Two types of oblique drawings cavalier cabinet

Review Questions 3-5

Cavalier Oblique The entire drawing uses the same scale Sometimes creates a distorted appearance

Which is the cube ?

Were you right?

Cavalier Oblique Front view true size Receding Axis Angle (Normally 30°, 45° or 60°) is Variable Depth dimension (receding axis) true size

Cabinet Oblique Front view true size Receding Axis Angle (Normally 30°, 45° or 60°) is Variable Depth dimension (receding axis) half size

Cavalier Oblique Drawing

Cabinet Oblique Measurements on the receding axes are reduced by half More visually realistic representation Often used for drawing cabinets

Cabinet Oblique Drawing

Side by Side Comparison Cavalier Oblique Cabinet Oblique

Review Questions 6-8

Perspective Drawings The most realistic of all pictorial drawings Receding lines in the drawing “meet” at a vanishing point instead of being parallel Eliminates distortion at the back part of pictorial drawings Two types parallel (one-point) perspective angular (two point) perspective

Perspective Drawing

Parallel Perspective (One Point) One face of the object is shown as the front view Lines parallel to the front view remain parallel Lines that are perpendicular to the front view converge at a SINGLE VANISHING POINT

Angular Perspective (Two-Point) Similar to isometric drawings One edge of the object is place in front The two faces that meet at this edge recede to DIFFERENT VANISHING POINTS All lines parallel to each face go to the different vanishing points

Angular Perspective Drawing

Types of Perspectives

Horizon Below Object

Exploded Pictorial Drawings Used to show relative position of parts or construction details Used to clarify assembly sequence Common in appliance and cabinetry service manuals

Exploded Pictorial Drawing