# Study Lesson 5 Pictorial sketching. Contents Freehand sketching techniques Pictorial projections -...

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Study Lesson 5

Pictorial sketching

Contents

Freehand sketchingtechniquesSketching is one of the primary modes of communication in the initial stages of the design process. Sketching also is a means to creative thinking. It has been shown that your mind works more creatively when your hand is sketching as you are engaged in thinking about a problem. [Lieu & Sorby 2009]

2-D geometry 1. Straight line (Horizontal, vertical and Inclined)2. Arc, circle and curveA two-dimensional geometry is always composed ofExampleUse your experiences gainedfrom the chapter applied geometry.Analyze the composition of 2-Dgeometry and list the constructionsteps.Suggestionfor practicing

Tools preparation & recommendations2. Sketching paper1. Pencil3. Eraser

Techniques : Sketching a lineVertical lines should sketchfrom top to bottom.Horizontal lines should sketchfrom left to right.Inclined lines that are mostlyvertical, sketch them fromtop to bottom.Inclined lines that are mostlyhorizontal, sketch them fromleft to right.Sketch the line in the following directionsFocus on the end point.+++++

Preferhorizontal linePrefervertical lineTechniques : Sketching a lineYou can rotate the paper on the desk to suit yourpreferences line tracing direction.

Techniques : Sketching an arcTo sketch an arc of a given radius it is necessary to use construction lines to locate its center and its tangent points.Explanation1. Sketch two lines intersect at the center of an arc.2. Sketch a square bounding box with the length of its sides equal to radius of an arc.3. Sketch a diagonal line. [option]4. Mark the point on diagonal line far from the center of an arc for a distance 2/3 of the length of the line.5. Sketch an arc through the tangent points and marked pointPlay1/32/3Radius of an arcRadius of an arc

Techniques : Sketching a small circleTo sketch a circle of a given diameter it is necessary to use construction lines to locate its center and its tangent points.Explanation1. Sketch two lines intersect at the center of a circle.2. Sketch a square bounding box with the length of its sides equal to radius of a circle.3. Sketch the diagonal lines. [option]4. Mark the point on diagonal line far from the center of a circle for a distance 2/3 of the half-length of the line.5. Sketch a circle through all marked points and tangent points.Play1/32/3Radius ofa circleRadius ofa circle

Place one pencils tip at the center as a pivot, and set another pencils tip at the radius-distance from the center.Hold the hand in this position and rotate the paper.Techniques : Sketching a large circle

Pictorialprojection

Types of a pictorial projectionParallel & normalto picture planeParallel & obliqueto picture planeAxonometric ProjectionOblique Projection

Type of an axonometric projection2. DimetricTwo anglesare equal.1. TrimetricNone of the anglesare equal.3. IsometricAll anglesare equal.Axonometricaxes

1. Cavalier2. CabinetType of an oblique projectionThis obliqued anglecan be any anglesbut for convenienta 45o is chosen

Isometric projectionvs. Isometric sketch

Isometric projection45The projected lengths of the edges parallel to the axonometricaxes are approximately 81% of their true length.3-D object (Cube)Axonometric projection35o16'Isometric view

Isometric sketchIsometric sketch has a similar shape as an isometric projection view except that their edges parallel to the axonometric axes are drawn in full size.Isometric projectionIsometric sketching/drawingForeshortenFull size

Angle & distance in isometric sketchAngles in an isometric sketch distort from the actual anglefound in the object.Actual or true distance can be measured along the isometriclines of the isometric sketch.Example 90o angleappears as 120o.90o angleappears as 60o.CorrectWrong

Orientation of isometric axesIsometric axes can be arbitrarily oriented to create different views of a single object.RegularisometricReverse axisisometricLong axisisometricView point is lookingdown on the top ofthe object.View point is lookingup on the bottom ofthe object.View point is lookingfrom the right (or left)of the object.

Class activity : Identify the nonisometric linesClick on the following buttonthat you think that it representsan nonisometric line.ABBCCDDEEFAFBGCHDIEIFJGHHIIJ

Isometric sketchingFrom an orthographic views

Overview of the process1. Analyze the alignment of a given orthographic viewsProceduresExamples2. Select a suitable orientation of isometric axes.FrontFrontTFRBFRTFLFront3. Interpret the lines/areas in orthographic views as a plane or surface.4. Sketch that plane or surface in an isometric axes.FrontNormalplane

Sketching a normal planeFront-Right-TopFront-Right-BottomFrontFrontGivenGiven

Class activity : Sketching a normal planeFront-Right-BottomGiven1. View alignment is2. Identify the front view3. Sketch the plane (1 min)FrontAnswer

Sketch an inclined planeFront-Right-TopFrontGivenDid you see that the parallel lines in orthographic views still be the parallel lines in an isometric sketch?

Front-Right-TopGiven1. View alignment is2. Identify the front view3. Sketch the plane (1 min)AnswerClass activity : Sketching an inclined planeFront

Sketching a circle and an arc (appeared on the normal plane)Circle appears as ellipse in a pictorial sketch.In case of isometric sketch, the ellipse is called isometric ellipse.The square that circumscribes an isometric ellipse is called isometric square. Isometric ellipseIsometric squareTangent pointsTangent points

Isometric ellipses : Their orientations

Play3. Sketch diagonal lines.5. Draw the arcs through the marked and tangent points.Explanation2. Sketch an isometric square.1. Locate the center of an ellipse by two isometric lines. Isometric ellipses : Sketching method4. Mark the point on diagonal line far from the center of an ellipse for a distance 2/3 of the half- length of the line.1/32/31/32/3

3. Construct a perpendicular bisector from each tangent point.4. Locate the four centers.5. Draw the arcs with these centers and tangent to isometric square.ExplanationSuitable for the case of instrumental drawing.2. Sketch an isometric square.1. Locate the center of an ellipse. Isometric ellipses : Four-center methodPlay

Sketching an arcIsometric arc is a part of anisometric circle.Steps for sketchingan isometric arc are1. Locate its center by two isometric lines.2. Create an isometric square circumscribes an arc.3. Draw a radial diagonal line.4. Divide the diagonal line into 3 equal parts.5. Sketch an arc.1/32/32/31/390o arc180o arcPlayTry to sketch an arc orientedon a different planes by yourself

Front-Bottom-RightFrontGivenExample

1. In orthographic views, choose a finite number of points along the curve. 2. Plot these points in the isometric axes.3. Sketch the curve.The concept used is similar to plotting a curve.Sketching an irregular curve (appeared on the normal plane)

Isometric sketchingof an object

Guidance 1A parallel line always parallel to each other regardless ofthe kind of views, i.e. orthographic and isometric views. The third dimension of an object is created by extruding a 2D geometry or surface.It helps us control the shape of the sketch.Examples 11.Sketch the front viewExplanation2. There are parallel lines along the depth direction. 3. Extrude the front surface4. Sketch the rear surface.In this example, hidden lines can be omitted.

Guidance 1Examples 2 A parallel line always parallel to each other regardless ofthe kind of views, i.e. orthographic and isometric views. The third dimension of an object is created by extruding a 2D geometry or surface.It helps us control the shape of the sketch.1.Sketch the top viewExplanation2. There are parallel lines along the height direction. 3. Extrude the top surface4. Sketch the bottom surface.In this example, hidden lines can be omitted.

Guidance 1Examples 3A parallel line always parallel to each other regardless ofthe kind of views, i.e. orthographic and isometric views. The third dimension of an object is created by extruding a 2D geometry or surface.It helps us control the shape of the sketch.

Guidance 2Examples 4Many of the complex shape objects come from a combination of a simple shape object.Strategy 1 : Sketch a group of simple objects before combining them.Strategy 2 : Sketch a main body of an object before gradually adding details or modifying.+Hidden lines are omitted becauseplanes of each object becomes a singleplane

Guidance 2Examples 5Many of the complex shape objects come from a combination of a simple shape object.Strategy 1 : Sketch a group of simple objects before combining them.Strategy 2 : Sketch a main body of an object before adding details or modifying.Omit center lines for clarity.Hidden linecan be omittedwithout losing object information

Suggestion for practicing1. Pick up 2 or 3 simple shape objects.2. Choose a prefer combination method.3. Sketch the result.Strategy 11. Pick up one simple shape object.2. Identify a prefer modification.3. Sketch the result.Strategy 2ExampleExample= ?= ?= ?

FrontExample : object modification (strategy 2)FrontFrontModify byaddinga shallow holeModify byaddinga base

Obliquesketching

Example : Advantage of an oblique sketchIsometricOblique (cavalier)E

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