Slide 1What is ISOMETRIC?
It is a method of producing pictorial view of an object showing all three faces of the object simultaneously.
It is a type of parallel projection
It is a type of axonometric projection
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Axonometric Projections
Projectors parallel to each other and perpendicular to projection plane
Object is inclined with respect to projection plane
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All angles between axonometric axes are equal
The three coordinate axes of the object appear equally foreshortened (about 3/4th of true length)
The angles between any two of the three coordinate axes is 120°
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Isometric Terminology
Any line parallel to isometric axes is called isometric line
A  non-isometric line is a line not parallel   to   any   one   of   the three isometric axis
In isometric projection of cube, the faces of the cube and any plane parallel to them is called isometric planes
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Isometric Scale
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AEBO is isometric, cube is rotated to obtain AE’BO’ (actual face of cube)
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Isometric Drawing
Isometric Projection: Drawing prepared with isometric scale on isometric axes
Isometric Drawing:
Drawing prepared
Compared to isometric projection, Isometric drawing has a chunkier overall impression
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Step 1
Isometric sketches begin with defining isometric axes, three lines, one vertical and two drawn at 30° from the horizontal.
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Step 2
Three lines of the isometric axes represent the three primary dimensions of the object: width, height, and depth
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Step 5
Add details to the block starting from the front face. Then add details to the other faces.
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Step 6
Darken all visible lines to complete the isometric sketch. (make sure that construction lines are light)
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Axonometric projection shows all 3 dimensions, length, width and height.
The isometric lines are only drawn to scale. Objects composed entirely of isometric lines can be drawn by taking all measurements parallel to main edges of the enclosing box.
Non-isometric lines are drawn by transferring the ordinates (which are on isometric lines) of the end of the lines
Inclined and oblique surfaces are drawn using end coordinates. Box construction and offset measurements are common methods
In  an  isometric  drawing,  an angle never appears in its true size. Angles, irregular curves require special techniques
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Hidden detail is omitted unless it is necessary to show shape of object
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Hidden detail is omitted unless it is necessary to show shape of object
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Make an Isometric Drawing with corner A at the bottom
NON-ISOMETRIC LINE
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Hidden detail is omitted unless it is necessary to show shape of object
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Non-isometric lines are drawn with box construction and offset measurements
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Hidden detail is omitted unless it is necessary to show shape of object
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Irregular Objects
Make an Isometric Drawing of the following irregular object (pyramid)
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Irregular Objects
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Hidden detail is omitted unless it is necessary to show shape of object
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Objects with Circular Geometry
A circle in a orthographic projection will appear as an ellipse in an isometric drawing.
Instead of actual ellipses often approximate ellipses are drawn for isometric drawing.
Four-centre ellipses are used to approximate ellipses on isometric planes.
How to draw four-centre ellipse???
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Approximate Ellipse
Draw  the  isometric centre  lines  of  the circle. Using  the  centre  lines,  draw an isometric square with sides equal to the diameter of  the  circle.
From  the  near  corners  of  the  box,  draw two large arcs with radius R, using the two red points as centres.
Draw the two smaller arcs with radius r, using two green points as centres.
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Hidden detail is omitted unless it is necessary to show shape of object
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Make an Isometric Drawing of the following curved object
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Objects with Non-Circular Curved Surfaces
A line that appears as a noncircular curve in a normal orthographic view of an object appears as a non-isometric line in an isometric drawing.
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