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Ch.5 Pictorial Drawings. Objective: Learn how to construct three types of pictorial drawings – Isometric, oblique, and perspective.
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Ch.5 Pictorial Drawings Objective: Learn how to construct three types of pictorial drawings – Isometric, oblique, and perspective • Isometric drawings (6.1 & 6.2) Theory of isometric projection (fig5.9), Position of isometric axes (fig6.10 to 12), Standards for hidden lines, center lines, and dimensioning (fig6.13 to 15), isometric drawing construction (fig6.17 to 42) • Oblique drawings (6.3) Oblique projection theory & classification (fig6.46 to 50), object orientation rules (fig5.51 to 55), dimensioning (fig6.65), oblique drawing construction (fig6.56 to 64) • Perspective drawings (6.4-6.7) Perspective vs. orthogonal (fig6.69), vanishing point position and ground line position (fig6.17 & 6.73), classification of perspective drawing (fig6.74), perspective drawing variables selection (6.7).
Examples Perspective
Isometric drawings • Depending on where you place isometric axes, you get different views (Use the most effective position to meet your need)
About isometric and non-isometric lines and planes True-length distances can only be measured along isometric lines, that is, lines run parallel to any of the isometric axes.
Dealing with hidden lines and center lines in isometric drawings Hidden lines are omitted unless they are absolutely necessary. Center lines are drawn only for showing symmetry or for dimensioning. Normally center lines are not shown.
Constructing an isometric drawing using the Boxing-In method Box in from the outmost shape to inside details.
What if you have non-isometric lines? Remember that true-length distances can only be measured along isometric lines, that is, lines run parallel to any of the isometric axes.
What if you have curves? use the Off-set Coordinate method works.
Oblique Drawings • Oblique projection is a form of parallel projection in which the projectors are parallel to each other but are not perpendicular to the projection plane. Common oblique angles
Oblique drawing types: cavalier, cabinet, and general oblique
Some hints to select the most important object face • In oblique projection, first, the object face that is placed parallel to the frontal plane will be drawn true size and shape.
Dimensioning in oblique drawings • In oblique drawings, dimensions lie in the plane of the surface to which they apply, and unidirectional text placement is used. Dimension text may need to be changed because only the cavalier oblique projection gives true depth.
Constructing an oblique drawing using the Offset Coordinate method • When we have arcs and curves, this method is always the easiest method.
Perspective drawings • Terms that you want to be familiar with: horizon line, ground line, station point, picture plane (projection plane), and vanishing point.
Position of the vanishing point and ground line and resulting perspective projections
One-, two-, and three-point perspective drawings • 4 variables in perspective drawings: • Distance of object from picture plane • Position of station point • Position of ground line • Number of vanishing points