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Technical Sketching. Chapter 3. 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 . Objectives (cont.).

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  • 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
objectives cont
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
understanding solid objects
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
types of solids
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
types of solids7
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
types of solids9
Types of Solids
  • Prisms
    • A prism has two bases which are parallel equal polygons
types of solids10
Types of Solids
  • Pyramids
    • A pyramid has a polygon for a base and triangular lateral faces which intersect at a vertex
types of solids11
Types of Solids
  • Cylinders
    • A cylinder has a single-curved exterior surface
types of solids12
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
types of solids13
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
types of solids15
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
understanding sketching techniques
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
understanding sketching techniques17
Understanding Sketching Techniques
  • Essential shapes can be blocked in using construction lines
understanding sketching techniques18
Understanding Sketching Techniques
  • Contours show the contrast between positive and negative space
  • 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
  • Adding shading to a sketch can give it a more realistic appearance
    • Hatching lines and stippling are common forms of shading
edges and vertices
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
points and lines
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
points and lines25
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
  • 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
drawings and sketches
Drawings and Sketches
  • The following skills are important for sketches and drawings:
    • Accuracy
    • Speed
    • Legibility
    • Neatness
freehand sketching
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
line weights
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
maintaining proportions
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
one view drawings
One View Drawings
  • Frequently a single view supplemented by notes and dimensions can describe a simple object
pictorial sketching
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
pictorial sketching35
Pictorial Sketching
  • The three common methods used to sketch pictorials are:
    • Isometric sketching
    • Oblique sketching
    • Perspective sketching
oblique sketches
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
oblique sketches37
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
perspective pictorials
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