In most cases, a single view is not sufficient to show all necessary features, and several views are used. Types of views include the following:
Orthographic Projection
The orthographic projection shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either first-angle or third-angle projection.First angle projection is the ISO standard and is primarily used in Europe. The 3D object is projected into 2D "paper" space as if you were looking at an X-ray of the object: the top view is under the front view, the right view is at the left of the front view. Third angle projection is primarily used in the United States and Canada, where it is the default projection system according to BS 8888:2006, the left view is placed on the left and the top view on the top. Not all views are necessarily used, and determination of what surface constitutes the front, back, top and bottom varies depending on the projection used.
Auxiliary Projection
An auxiliary view is an orthographic view that is projected into any plane other than one of the six principal views. These views are typically used when an object contains some sort of inclined plane. Using the auxiliary view allows for that inclined plane (and any other significant features) to be projected in their true size and shape. The true size and shape of any feature in an engineering drawing can only be known when the Line of Sight (LOS) is perpendicular to the plane being referenced.
Isometric Projection
The isometric projection show the object from angles in which the scales along each axis of the object are equal. Isometric projection corresponds to rotation of the object by ± 45° about the vertical axis, followed by rotation of approximately ± 35.264° [= arcsin(tan(30°))] about the horizontal axis starting from an orthographic projection view. "Isometric" comes from the Greek for "same measure." One of the things that makes isometric drawings so attractive is the ease with which 60 degree angles can be constructed with only a compass and straightedge.
Isometric projection is a type of axonometric projection. The other two types of axonometric projection are: dimetric projection and, trimetric projection.
Oblique Projection
An oblique projection is a simple type of graphical projection used for producing pictorial, two-dimensional images of three-dimensional objects; it projects an image by intersecting parallel rays (projectors), and from the three-dimensional source object with the drawing surface (projection plan).
In both oblique projection and orthographic projection, parallel lines of the source object produce parallel lines in the projected image.
Perspective
Perspective is an approximate representation on a flat surface, of an image as it is perceived by the eye. The two most characteristic features of perspective are that objects are drawn; smaller as their distance from the observer increases, foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
Friday, February 26, 2010
Engineering Drawings: Line Styles
Standard engineering drawing line types
A variety of line styles graphically represent physical objects. Types of lines include the following:
Visible – are continuous lines used to depict edges directly visible from a particular angle.
Hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
Center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
Cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views.
Section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."
A variety of line styles graphically represent physical objects. Types of lines include the following:
Visible – are continuous lines used to depict edges directly visible from a particular angle.
Hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
Center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
Cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views.
Section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."
Engineering Drawings: Common Features
Drawings convey the following critical information:
Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various standard directions, such as front, top, side, etc.
Dimensions – the size of the object is captured in accepted units.
Tolerances – the allowable variations for each dimension.
Material – represents what the item is made of.
Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery.
Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various standard directions, such as front, top, side, etc.
Dimensions – the size of the object is captured in accepted units.
Tolerances – the allowable variations for each dimension.
Material – represents what the item is made of.
Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery.
Tuesday, February 23, 2010
Thursday, February 18, 2010
Incompleted Shelby on Sketchup
This is the incompleted 67' Ford Mustang Shelby I made on Google Sketchup. It was a good idea for a project, however Sketchup was not the right program to build it. It was fairly inaccurate and hard to line-up due to the inconvient snap function. Finding the blueprints for the car was very easy; a website supplied all the drawings and you simply had to download the picture. Once downloaded, to converted the image to a JPEG image on Photoshop then imported the JPEG image into Sketchup.
Tuesday, February 16, 2010
Isometric Projection
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Isometric drawing is way of presenting designs/drawings in three dimensions. The example below has been drawn with a 30 degree set square. Designs are always drawn at 30 degrees in isometric projection. It is vital that drawing equipment such as T-squares and 30/60 degree set squares are used carefully. The drawing paper should be clip securely to a drawing board.
Isometric drawing is way of presenting designs/drawings in three dimensions. The example below has been drawn with a 30 degree set square. Designs are always drawn at 30 degrees in isometric projection. It is vital that drawing equipment such as T-squares and 30/60 degree set squares are used carefully. The drawing paper should be clip securely to a drawing board.
Oblique Projection
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Oblique projection is a method of drawing objects in 3 dimensions. It is quite a simple technique compared to isometric or even perspective drawing. However, to draw accurately in oblique projection traditional drawing equipment is needed, such as rulers, drawing boards, T-squares, set squares, etc.
Oblique projection is a method of drawing objects in 3 dimensions. It is quite a simple technique compared to isometric or even perspective drawing. However, to draw accurately in oblique projection traditional drawing equipment is needed, such as rulers, drawing boards, T-squares, set squares, etc.
Artistic/Perspective Drawing
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1. Single Point Perspective Drawing
Perspective drawing is a good style to use when drawing in 3D. There are different styles including single point and two point perspective. The basic example below shows how to construct a simple single point perspective drawing of a cube. Using the same skills more complex drawings/designs can be drawn, after a little practice.
2. Two Point Perspective Drawing
Perspective is a realistic way of drawing objects in 3D. We have already looked at single point perspective, two point perspective using two vanishing points and when an object is drawn in this way it is even more realistic than if it were to be drawn with a single vanishing point.
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