Lesson Notes By Weeks and Term - Junior Secondary School 3

TERM: FIRST TERM

SUBJECT: BASIC TECHNOLOGY

CLASS: JSS 3

REF MATERIALS

• EVANS BASIC TECH FOR JSS BOOK 3
• NERDC BASIC TECH FOR JSS BOOK THREE

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WEEK SEVEN AND EIGHT

TOPIC: OBLIQUE DRAWING AND PERSPECTIVES

CONTENT

1. Meaning of oblique drawing
2. Methods of drawing oblique drawing
3. Meaning of perspective drawing�
4. Classes of perspective drawing

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OBLIQUE DRAWING:� This is a method of drawing the shape of solid object in which the projection angles are drawn at an angle450to the horizontal plane. It recognizes objects in three (3) dimensions i.e. length, breadth, and depth.

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ACTIVITY: Produce an oblique drawing of an isometric drawing of a rectangular block with the given dimension � length 50mm, width 30mm and� height 70mm.

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METHODS OF DRAWING OBLIQUE

1. CAVALIER METHOD: when the receding axis of an angle 450 is drawn in full length
2. CABINET OBLIQUE:� this is whenthe receding axis of an angle 450is half the length.

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EVALUATION

1. Define oblique drawing.
2. Differentiate between cavalier type of oblique drawing and cabinet oblique drawing.

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PERSPECTIVE DRAWING

This is a method of drawing the shape of solid object such that the THREE sides of an object are shownat once. Of all the pictorial drawing, it is the closest to how the eye actually sees objects.

Their principal distinguishing feature is that they make allowance for the fact that as an object recedes from the eye, the image observed by the eye become smaller.

In perspective drawing, all the lines of an object converge to a point called varnishing point.

Varnishing point is the point in the perspective drawing where all thevisual rays converged. This can be classified according to the number of varnishing point the drawing may have, the number of varnishing point depends on the position of the object with respect to the picture.

1. One point perspective means one varnishing point
2. Two point perspective means two varnishing point.

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ONE POINT PERSPECTIVE DRAWING: Here the four parallel edges of the cube are converged at a particular point called varnishing point.

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TWO POINT PERSPECTIVE DRAWING: this contains two varnishing pointsand the two varnishing point appears at a point in two directionscalled sight line.

A perspective drawing is not drawn to scales and does not give any information about hidden details.

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EVALUATION

1. Define perspective drawing
2. What is varnishing point?

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GENERAL EVALUATION

1. Using one point perspective draw a cube
2. Differentiate between one point perspective and two point perspective
3. Using oblique drawing draw a rectangle of length 70mm/width 50mm and height 40mm.

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READING ASSIGNMENT

Read orthographic drawing.

Ref book: NERDC, Basic Tech for JSS book Three. Pg. 50-60.

WEEKEND ASSIGNMENT

1. A pictorial drawing of solid objects projected at angle 450 is called A. varnishing point B. isometric drawing� C. oblique drawing D. perspective drawing.
2. The point in the perspective drawing where all the visual rays converge at appoint is called______ A. varnishing point B. perspective point C. annealing point D. orthographic drawing.
3. Which of the following is a method of drawing oblique drawing A. casting method B. extrusion method� C. cavalier method D. rotary method.
4. __________ contains two varnishing points and the two varnishing point appear at a point in two directions called sight line.A. One point perspective B.Two point perspective C. Cabinet drawing D. Cavalier method.
5. The method of drawing shapes of solid objects such that it shows the three sides of an object at once is called_____A. scale drawing B.� perspective drawing C. orthographic drawing D. oblique drawing.

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THEORY

1. With the aid of diagram draw one point perspective view of a cube.
2. Differentiate between one point perspective view and two point perspective view.

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