Dr. Anwar Abu-Zarifa. Islamic University Gaza. Industrial Engineering Department1 Unit 5 Shap Description (Orthographic Projection) نظرية الأسقاط

Dr. Anwar Abu-Zarifa . Islamic University Gaza . Industrial Engineering Department 11

Unit 5Unit 5Shap DescriptionShap Description(Orthographic Projection)(Orthographic Projection)

نظرية األسقاط


Even simple, primitive shapes often need several views to fully describe their topology.


Holes and cylinders may appear “True Shape and Size” (TSS), or foreshortened depending on the view in which they appear. (Foreshortened circles will appear as ellipses.)



Orthographic ProjectionOrthographic ProjectionOrthographic projection (sometimes referred to as multi-view projection), is a geometric procedure used in the engineering disciplines to project multiple graphic images of three-dimensional objects, onto a single two-dimensional plane. The procedure is also called engineering drawing or drafting, and is the primary means of communication used by designers and engineers in the design process.

Multiple views in an orthogonal orientation (each rotated 90º from the other), is fundamental to the definition of feature and part characteristics such as size, location, orientation, and functional relationships.

The object can only be viewed from the front, top, right side, left side, back, or bottom. With the images indelibly fixed on the planes, and the box unfolded, the projected images or views would always be oriented orthographically, and aligned with each other, from view to view on the drawing.


Ortho means “at 90 degrees”, and is a form of parallel projection.

Orthographic projections are used to show several views of the same object in one drawing set.


Orthographic Projection TheoryOrthographic Projection TheoryObservation of an object begins with the direction from which the object is to be Observation of an object begins with the direction from which the object is to be viewed—the viewed—the line of sight.line of sight.


Viewing StationViewing Stationat Infinityat Infinity

Orthographic Projection TheoryOrthographic Projection Theory

The viewing station for the observer is always an infinite distance from the object.The viewing station for the observer is always an infinite distance from the object.


Line of SightLine of Sight


Projection PlaneProjection Plane(Picture Plane(Picture PlaneViewing Plane)Viewing Plane)


The plane of projection is located between the viewing station and the object The plane of projection is located between the viewing station and the object (third angle projection).(third angle projection).






The line of sight is always normal to the plane of projectionThe line of sight is always normal to the plane of projection


ObjectObject





The object may be located anywhere behind the plane of projectionThe object may be located anywhere behind the plane of projection


Parallel Visual RaysParallel Visual Rays


ObjectObject




Because the observation location is at infinity, Because the observation location is at infinity, parallelparallel visual rays extend from the visual rays extend from the object to the plane of projection, and produce the image on the projection plane.object to the plane of projection, and produce the image on the projection plane.

Dr. Anwar Abu-Zarifa . Islamic University Gaza . Industrial Engineering Department

GLASS BOX CONCEPTGLASS BOX CONCEPT


The glass box concept theorizes that an object is suspended inside a six-sided glass cube The glass box concept theorizes that an object is suspended inside a six-sided glass cube (notice the use of hidden lines on the glass box, depicting lines that would not be visible (notice the use of hidden lines on the glass box, depicting lines that would not be visible from the given perspective). from the given perspective).


As the object is viewed from a specific orientation (perpendicular to one of the sides of the cube) visual As the object is viewed from a specific orientation (perpendicular to one of the sides of the cube) visual rays project from the object to the projection plane. These projectors are rays project from the object to the projection plane. These projectors are alwaysalways parallel to each other. parallel to each other.


The object’s image is formed on the The object’s image is formed on the FrontalFrontal projection plane by the pierce points of the projection plane by the pierce points of the visual rays.visual rays.


The process is repeated to construct the right side view on the The process is repeated to construct the right side view on the profile planeprofile plane


Similarly, the top view is projected Similarly, the top view is projected to the to the horizontal planehorizontal plane


For many three-dimensional objects, two to three orthographic views are For many three-dimensional objects, two to three orthographic views are sufficient to describe their geometry.sufficient to describe their geometry.


The box can be unfolded to show the The box can be unfolded to show the multiple views in a single x-y planemultiple views in a single x-y plane


FRONT

TOP

RIGHT SIDE

Because the observation point is located at Because the observation point is located at infinity, the integrity of feature size and infinity, the integrity of feature size and location are maintained, and the views are location are maintained, and the views are oriented orthogonally in relationship to each oriented orthogonally in relationship to each other.other.


FRONT

TOP

RIGHT SIDE

Notice that the projectors or extension lines, are Notice that the projectors or extension lines, are perpendicular to the folding lines of the glass perpendicular to the folding lines of the glass box. (Fold lines and extension lines are drawn box. (Fold lines and extension lines are drawn very lightly, when used, and are very lightly, when used, and are notnot part of the part of the finished drawing.)finished drawing.)


Dimensional Data Can then be added to the drawingDimensional Data Can then be added to the drawing

Notice the three basic line types:Notice the three basic line types:

•Solid – A Visible EdgeSolid – A Visible Edge

•Hidden - An Invisible EdgeHidden - An Invisible Edge

•Center – Center of a Cylinder (Internal or Center – Center of a Cylinder (Internal or External)External)


The Glass Box Concept The Glass Box Concept

Click on image to animate - click outside for next slide


ORIENTATION OF OBJECT FEATURES IN ORTHOGRAPHIC PROJECTION

ORIENTATION OF OBJECT FEATURES IN ORTHOGRAPHIC PROJECTION


RIGHT SIDE

d

h

FRONT

TOP

d

w

w

h

Directional Orientation in Orthographic Projection Directional Orientation in Orthographic Projection

Two or three views of a 3-dimensional Two or three views of a 3-dimensional object are often sufficient for a complete object are often sufficient for a complete definition of part geometrydefinition of part geometry. Width and . Width and depth are displayed in the top view; height depth are displayed in the top view; height and width in the front view, height and and width in the front view, height and depth in the side view.depth in the side view.

Height = hWidth = wDepth = d


DIRECTION AND ORIENTATION DIRECTION AND ORIENTATION ININ

ORTHOGRAPHIC PROJECTIONORTHOGRAPHIC PROJECTION

(PRINCIPAL PROJECTION PLANES)(PRINCIPAL PROJECTION PLANES)


FIRST-ANGLE PROJECTIONFIRST-ANGLE PROJECTION


Projection methods:

3RD Angle (US Standard)

ISO (1ST Angle Metric Standard)

NOTE:

Reverse construction methods work just as well in 1ST Angle projection.


11stst angle and 3 angle and 3rdrd angle Orthographics... The difference: angle Orthographics... The difference:

3030

Third-angle Projection

First-angle Projection

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Dr. Anwar Abu-Zarifa. Islamic University Gaza. Industrial Engineering Department1 Unit 5 Shap Description (Orthographic Projection) نظرية الأسقاط