Pictorial Projection.pdf

Fall2005- ENGR 3200U 1

Pictorial Projection


Axonometric Projection

Axon Metric

Axis To Measure

Greek


Axonometric ProjectionDefinition:A parallel projection technique used to create a pictorial of an object by rotating the object on an axis relative to the projection, or picture plane


Four Principle Projection Techniques

A & B & C observer at infinity

A & B are orthographic


Difference between multiview and axonometric drawing

In multiview only two dimensions are visible in each view

In Axonometric the object is rotated and tilted to display all three dimensions


Classification of Axonometric ProjectionClassification by the angles between the lines comprising the axonometric axes.

Pleasing to the eye Easy to draw


Isometric Projection1- Rotation 45 about a vertical axis 2- Tilt the object forward till the body

diagonal AB appears as a point in the front view


Isometric ProjectionThe tilting angle is 35 and 16'Isometric Axes: The three axes meet at A, B form equal angles of 120Isometric Line: Any line parallel to an isometric axisIsometric Plane: Any plane parallel to the cub faces


Isometric Scale

Isometric orientating Foreshortening

Isometric scale = Cos (35, 16') = 0.81647

Approximately 80% of the true lengths

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Isometric Scale

Isometric Drawing = Isometric projection 1.23

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Creating the Isometric Scale

Or approximation with a scale

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Size Comparison;Isometric Drawing and True Isometric Projection

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Four Types of Isometric Drawings

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Hidden LinesOnly when it is absolutely necessary

Choose the most descriptive view

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Center LinesFor dimensioning or to show the symmetry

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Dimensioning based on ANSI Y14.4 19891) Dimension lines, extension

lines, and line being dimensioned shall lie in the same plane

2) All dimensions and notes should be unidirectional, reading from bottom upward

3) All dimensions and notes should be located outside of the view whenever possible

For Production

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Dimensioning based on ANSI Y14.4 1989Aligned Dimensioning

For illustration

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Isometric Ellipses

1) Major and minor axes are always perpendicular

3) On the top plane, major axis is horizontal and the minor axis is vertical

4) Major axis is always perpendicular to the axis of the hole

To represent holes and cylinders in the isometric views

2) Major axes are measured 60 to the horizontal on the front and the profile planes

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Isometric Ellipse Templates

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Angles in Isometric Views

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Irregular Curves in Isometric Views

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Isometric Assembly Drawing

1- Assembled2- Exploded

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Isometric Assembly DrawingApplication in production & instruction manuals

balloons

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Oblique Projection

A pictorial drawing in wich the most descriptive or natural view is treated as the front view and is placed parallel to the plane of projection

Favored by furniture manufacturer & cabinetmakers

Excessive distortion

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Orthographic & Oblique Projections

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Oblique Projection TheoryA parallel projection in which the projections are not perpendicular to the projection plane The actual angle of projection is not fixed

However angle between 30 and 60 degrees are preferred

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Classifications of Oblique Drawing1- Cavalier2- Cabinet3- General

Front surfaces are drawn true size and receding angle is usually between 45 and 60 degree

Anywhere from full to half length

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Comparison of Cavalier & Cabinet Oblique Drawings

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Oblique Orientation Rules

Place complex features parallel to the frontal plane

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Place the longest dimension of the object parallel to the frontal plane

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The first rule override the second rule

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Oblique Projection Sketching

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Perspective Projection

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Perspective Projection Terminology

Perspective drawing and orthographic side view of a roadThe line that sky meets the ground = Horizon Line = Eye Level

1- Objects positioned in the picture plane are shown true size2- as objects move further behind the picture plane, they are projected as smaller images3- All parallel lines, not parallel to the picture plane, converge at the vanishing point.

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Vanishing PointAn object positioned at an infinite distance from the picture plane appears as a point, called the vanishing point

Changing the vanishing point changes the perspective view

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Ground Line Position

Ground line represents the plane on which the object rests

Changing the ground line position changes the perspective view

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Classifications of perspective Projection Parallel or one

point perspective

Angular or two point perspective

Three point perspective; no edge or plane is parallel to the projection plane

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Perspective Drawing Variables Selection

1- Distance of object from picture plane2-Position of station point3-Position of the ground line relative to horizonNumber of vanishing points

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Procedure of on-point perspective sketch

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Pictorial Projection.pdf