Technical Sketching Chapter 3

2 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Objectives Define vertex, edge, plane, surface, and solid Identify four types of surfaces Identify five regular solids Draw points, lines, angled lines, arcs, circles, and ellipses

3 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Objectives (cont.) Apply techniques that aid in creating legible well-proportioned sketches Apply techniques to draw irregular curves Create a single view sketch Create an oblique sketch Create a one-point perspective sketch Create an isometric sketch of an object

4 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Solid Objects Three-dimensional figures are referred to as solids Solids are bounded by the surfaces that contain them These surfaces can be: Planar Single-curved Double-curved Warped

5 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Solid Objects

6 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Polyhedra Solids that are bounded by plane surfaces These planar surfaces are also referred to as faces of the object A polygon is a planar area that is enclosed by straight lines

7 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Regular polyhedra If the faces of a solid are equal regular polygons it is a regular polyhedron There are five regular polyhedra: Tetrahedron Hexahedron Octahedron Dodecahedron Icosahedron

8 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids

9 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Prisms A prism has two bases which are parallel equal polygons

10 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Pyramids A pyramid has a polygon for a base and triangular lateral faces which intersect at a vertex

11 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Cylinders A cylinder has a single-curved exterior surface

12 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Cones A cone has a single-curved exterior and can be formed by moving one end of a straight line around a circle while keeping the other end fixed at a point

13 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Sphere A sphere has a double-curved exterior that can be formed by revolving a circle around one of its diameters Torus A torus is shaped like a donut and has a double curved boundary surface

14 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids

15 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Types of Solids Ellipsoids An oblate or prolate ellipsoid is shaped like an egg and can be created by revolving an ellipse around one of its axes

16 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Sketching Techniques Analyzing complex objects The ability to break down complex shapes into simpler geometric primitives is an essential skill for sketching and modeling objects Basic curves and straight lines are the basis of many objects

17 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Sketching Techniques Essential shapes can be blocked in using construction lines

18 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Understanding Sketching Techniques Contours show the contrast between positive and negative space

19 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Viewpoint As you sketch, you should maintain a consistent viewpoint Examine the shapes you see from that viewpoint Sketch the object as it actually looks, not how you envision it is

20 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Shading Adding shading to a sketch can give it a more realistic appearance Hatching lines and stippling are common forms of shading

21 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Edges and Vertices An edge is formed where two surfaces intersect Edges are represented by visible or hidden lines A vertex is formed where three or more surfaces intersect The end of an edge is a vertex

22 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Edges and Vertices

23 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Points and Lines A point represents a location in space and has no width, height, or depth Points in drawings are represented by: The intersection of two lines A short crossbar on a line A small cross Points are not represented by simple dots

24 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Points and Lines

25 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Points and Lines A line is used in drawings to represent the edge of a solid object A straight line is the shortest distance between two points Lines may be parallel or perpendicular to other lines

26 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Points and Lines

27 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Angles An angle is formed by two intersecting lines There are 360 degrees in a full circle A degree is divided into 60 minutes A minute is divided into 60 seconds Angles may be complementary or supplementary

28 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Angles

29 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Drawings and Sketches The following skills are important for sketches and drawings: Accuracy Speed Legibility Neatness

30 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Freehand Sketching Freehand sketches are a helpful way to organize thoughts and record ideas The degree of precision of a given sketch depends on its use A freehand sketch should show attention to proportion, clarity, and correct line widths

31 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Line Weights Make dimension, extension, and centerlines thin, sharp, and black Make hidden lines medium and black Make visible and cutting plane lines thick and black Make construction lines thin and light

32 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Maintaining Proportions Sketches are not usually made to a specific scale The most important rule in freehand sketching is to keep the sketch in proportion Grid paper can help you maintain proportions

33 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. One View Drawings Frequently a single view supplemented by notes and dimensions can describe a simple object

34 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Pictorial Sketching A pictorial sketch represents a 3D object on a sheet of 2D paper by orienting the object so you can see its width, height, and depth in a single view

35 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Pictorial Sketching The three common methods used to sketch pictorials are: Isometric sketching Oblique sketching Perspective sketching

36 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Oblique Sketches In oblique drawing, circles and angles parallel to the projection plane are true size and shape Three things affect oblique sketches Which surface is parallel to the projection plane The angle and orientation for the receding lines depicting depth The scale chosen for the receding lines

37 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Oblique Sketches Forty-five degrees is often chosen for the angle of receding lines Thirty degrees is also a popular choice and can look more realistic In cavalier projection, receding lines are drawn at full scale In cabinet projection, the depth is represented at half scale

38 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Oblique Sketches

39 Technical Drawing 13 th Edition Giesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart © 2009 Pearson Education, Upper Saddle River, NJ All Rights Reserved. Perspective Pictorials Perspective pictorials approximate the view produced by the human eye Unlike parallel projection, perspective projectors converge at a vanishing point There are three types of perspective: One point Two point Three point