1. TA 101: Technical Arts 2015-16 II Dr. Prishati Raychowdhury Department of Civil Engineering IIT Kanpur Office: FB 336; Phone: 6692 E-mail: prishati@iitk.ac.inprishati@iitk.ac.in 1

2. Oblique Projection Lecture 9 2

3. Oblique Projection 30 o to 60 o Review Isometric Projection True Shape Details along depth axis 1.The oblique method is mainly used for objects with circular or curved features only one face or on parallel faces 2.For objects of this type the oblique is easy to draw and dimension 3.This is an widely used pictorial view 3

4. Receding Axis: 45 o to the Left and Up 4

5. Receding Axis: 30 o to the Right and Down 5

6. 30 0 Oblique Drawing Example 1 6

7. 7

8. Oblique Drawing Example 2 8 30 0

9. Object Orientation for Oblique 9

10. Rule I: Place the object with the irregular outline or contour parallel to the picture plane Note the greater distortion at B and C than at A Object Orientation for Oblique 10 B C

11. Object Orientation for Oblique 11 Rule II: The sides with the longest dimension should be placed parallel to the picture plane Note the exaggerated depth for B A B

12. Cavalier Oblique ViewCabinet Oblique View Two Types of Oblique Views 12 Note the exaggerated depth in Cavalier Cavalier 1:1:1 Cabinet 1:1:0.5 D D/2

13. Cavalier and Cabinet Oblique Views Cavalier View – Front View: True Shape – Receding Axis Angle Varies (30°, 45° or 60°) – Depth Dimension (Receding Axis) True Size Cabinet View – Front View: True Shape – Receding Axis Angle Varies (30°, 45° or 60°) – Depth Dimension (Receding Axis) Half Size 13

14. Cabinet Projection 14 The foreshortening of the z axis is done to provide a more “realistic” view

15. Example 3: 30 0 to the Right and Up 15

16. 90 50 40 30 0 90 50 65 50  20 40 25 R15 15 Example 4: Cavalier View 16 CAVALIER VIEW

17. Example 5: Cavalier View 17 200 80 2 holes  20  50  36  30 40 10 8 100 20

18.  80 130 50 40  60  50  35 30 20 8 8 8 8 4 CABINET VIEW Example 6: Cabinet View 18 20 25

19. Missing Lines and Views Next Topic 19

20. What could be this object? Understanding Simple Objects

21. Missing Line(s)

22. ??? Missing View

23. Missing Line/Views Objective is to complete a particular orthographic view for missing line(s) or draw a completely new view Information contained in a given views is synthesized to form the pictorial view to understand the object The basic principles of orthographic projections are used It is always a good idea to draw the pictorial sketch of the ‘possible’ object on a drawing sheet Information from one view is used to complete certain feature(s) in another view

24. Visualizing an Object: Useful Tips Break down a large object into smaller number of pieces of elemental geometrical forms e.g. square, circle, cylinder, prism, pyramid, cone, truncated cylinder/cone/prism, etc. The elemental blocks do not necessarily have to exist in the object and parts of it may be imaginary (helps in visualizing) These elemental parts may be either ‘additive’ or ‘subtractive’ in nature A pictorial image of the complex object can be formed by putting together elemental parts that are easy to visualize Such ‘detailed geometric analysis/dissection’ of a complex object helps in drawing the pictorial view of the object in the mind, which may then be sketched on paper

25. Try to visualize this object 1.There seems to be a half cylinder cut-out from a solid box 2.There seem to be two triangular pieces (thickness shown in top view) connected to the solid box (see front view) 3.There is a rectangular base and rectangular smaller piece in front 4.Base height is smaller than the height of another rectangular piece in front 5.There are two through holes on base Note: Drawing not to scale Visualizing an Object: Useful Tips

26. Solid box minus half cylinder Triangular pieces Rectangular BaseRectangular piece in front Through Holes Visualization of Objects

27. Consider this object Notice that most ‘elemental parts’ are ‘additive’. Which elemental parts are ‘subtractive’? It may be thought of consisting of many smaller elemental parts Visualizing an Object

28. Thank you.. 28