Visualization and DesignVisualization and Design

Engineering GraphicsEngineering Graphics

Stephen W. Crown Ph.D.Stephen W. Crown Ph.D.

ObjectiveObjective

How to represent a 3-D object effectively on a How to represent a 3-D object effectively on a 2-D drawing surface (pictorials)2-D drawing surface (pictorials)

How to visualize a 3-D object using solid How to visualize a 3-D object using solid primitivesprimitives

OverviewOverview

Sketching ReviewSketching Review PictorialsPictorials

• PerspectivePerspective• Parallel projectionParallel projection

Other Visualization ToolsOther Visualization Tools• Solid primitivesSolid primitives• MiscellaneousMiscellaneous

Sketching (review)Sketching (review)

DefinitionDefinition A rough freehand drawing used to document, A rough freehand drawing used to document,

communicate, and refine ideas developed primarily communicate, and refine ideas developed primarily in the ideation phase of the design processin the ideation phase of the design process

Follows standard practicesFollows standard practices A developed skillA developed skill Should be the first step of any CAD or Should be the first step of any CAD or

mechanical drawing (including homework mechanical drawing (including homework assignments) assignments)

Pictorial SketchesPictorial Sketches

Definition:Definition: A sketch developed for ease of A sketch developed for ease of visualization that shows an objects height, width, visualization that shows an objects height, width, and depth in a single viewand depth in a single view

Particularly useful for non-technical audiencesParticularly useful for non-technical audiences• Assembly drawingsAssembly drawings• Marketing Marketing

Helpful in the ideation phase of the design processHelpful in the ideation phase of the design process• How we picture objects in our mindHow we picture objects in our mind• How we visualize spatial relationshipsHow we visualize spatial relationships

Pictorial SketchesPictorial Sketches

Parallel ProjectionParallel Projection• Parallel lines are always drawn parallelParallel lines are always drawn parallel

• Easy to drawEasy to draw

• Often appears distortedOften appears distorted

• Two common typesTwo common types– Oblique PictorialsOblique Pictorials– Isometric PictorialsIsometric Pictorials

Perspective ProjectionPerspective Projection• Conveys information about distance and sizeConveys information about distance and size

• Not as common as parallel projectionNot as common as parallel projection

Parallel Projection PictorialsParallel Projection Pictorials

Oblique PictorialsOblique Pictorials• The simplest pictorial to sketchThe simplest pictorial to sketch• Surfaces which are parallel to the front face are Surfaces which are parallel to the front face are

undistorted as in a multiview drawingundistorted as in a multiview drawing– Circular features should be placed in the front view if Circular features should be placed in the front view if

possiblepossible– Draw the front face firstDraw the front face first

• Lines which are perpendicular to the front face are Lines which are perpendicular to the front face are drawn at an angle of 30 to 45drawn at an angle of 30 to 45oo

Parallel Projection PictorialsParallel Projection Pictorials

Oblique PictorialsOblique Pictorials• Cavalier ObliqueCavalier Oblique

– Depth is drawn full sizeDepth is drawn full size– Object looks distorted (depth is exaggerated)Object looks distorted (depth is exaggerated)

• Cabinet ObliqueCabinet Oblique– Depth is drawn to 1/2 of full sizeDepth is drawn to 1/2 of full size– Depth appears more accurate (2/3 is best)Depth appears more accurate (2/3 is best)

• Circular features which are not parallel to the Circular features which are not parallel to the front plane appear elliptical front plane appear elliptical

• TrimetricTrimetric• no equal anglesno equal angles• gives the most visually pleasing gives the most visually pleasing

viewview• DimetricDimetric

• Two equal anglesTwo equal angles• IsometricIsometric

• Three equal angles (120Three equal angles (120oo))• Height drawn along vertical axisHeight drawn along vertical axis• Width and depth drawn at 30Width and depth drawn at 30oo to to

horizontal axishorizontal axis• Other orientations (reversed and Other orientations (reversed and

long axis)long axis)

Axonometric PictorialsAxonometric Pictorials

Parallel Projection PictorialsParallel Projection Pictorials

Isometric PictorialsIsometric Pictorials• Most commonMost common• Surfaces on all principle planes are distortedSurfaces on all principle planes are distorted

– All circles appear as ellipsesAll circles appear as ellipses– Perpendicular lines are drawn at 60 or 120Perpendicular lines are drawn at 60 or 1200 0 anglesangles

• Height drawn along vertical axisHeight drawn along vertical axis• Width and depth drawn at 30Width and depth drawn at 30oo to horizontal to horizontal

axisaxis

Parallel Projection PictorialsParallel Projection Pictorials Isometric PictorialsIsometric Pictorials

• Begin drawing by blocking in height, width and depth Begin drawing by blocking in height, width and depth of entire object.of entire object.

• Continue to block in smaller featuresContinue to block in smaller features• Add curved surfaces lastAdd curved surfaces last

– circles appear as ellipsescircles appear as ellipses

– lines tangent to arcs locate the edge of curved surfaceslines tangent to arcs locate the edge of curved surfaces

• Isometric grid paper is often helpfulIsometric grid paper is often helpful– follow direction of axis and count intersectionsfollow direction of axis and count intersections

– use tracing paper or grid paper with light linesuse tracing paper or grid paper with light lines

Isometric Projection and Isometric Projection and Isometric DrawingsIsometric Drawings

• Rotate about the Z axis 45Rotate about the Z axis 45oo

• Rotate about the X axis by an angle of Rotate about the X axis by an angle of =sin=sin-1-1(2/3(2/3))½½

• An isometric projection is a true size projectionAn isometric projection is a true size projection length along projected axes is L*(2/3)length along projected axes is L*(2/3)½½

• An isometric drawing is drawn full scale along axesAn isometric drawing is drawn full scale along axes objects are increased in size by a factor of (3/2)objects are increased in size by a factor of (3/2)½½

Perspective Projection PictorialsPerspective Projection Pictorials The most difficult to drawThe most difficult to draw The most visually accurateThe most visually accurate The use of vanishing pointsThe use of vanishing points

• One point One point – Lines of height and width are parallelLines of height and width are parallel– Like a “perspective oblique”Like a “perspective oblique”

• Two pointsTwo points– Only lines representing height are parallelOnly lines representing height are parallel– most common perspective viewmost common perspective view

• Three pointsThree points– No lines are parallelNo lines are parallel

Other Visualization ToolsOther Visualization Tools

Solid primitivesSolid primitives• Box (Parallelepiped)Box (Parallelepiped)• CylinderCylinder• ConeCone• SphereSphere• WedgeWedge• Extrude a 2-D shapeExtrude a 2-D shape• Revolve a curve about an axisRevolve a curve about an axis

Other Visualization ToolsOther Visualization Tools Operations on solid primitivesOperations on solid primitives

• AddAdd– assemblyassembly– weldingwelding

• SubtractSubtract– drilling drilling – milling/machiningmilling/machining

• IntersectionIntersection– only regions where both part are in common are retainedonly regions where both part are in common are retained– helpful to produce mating partshelpful to produce mating parts

Other Visualization ToolsOther Visualization Tools Right hand ruleRight hand rule

• Your thumb, index finger, and middle finger Your thumb, index finger, and middle finger represent the X, Y, and Z axis respectively.represent the X, Y, and Z axis respectively.

• Point your thumb in the positive axis Point your thumb in the positive axis direction and your fingers wrap in the direction and your fingers wrap in the direction of positive rotationdirection of positive rotation

Other Visualization ToolsOther Visualization Tools Always rotate parts using full 90 degree Always rotate parts using full 90 degree

rotationsrotations Number vertices in different views of Number vertices in different views of

multiview and isometric drawingmultiview and isometric drawing PracticePractice