What Is A Multiview Drawing

A M ultiview drawing is one that shows two or more two-dimensional views of a three-dimensional object.

Multiview drawings provide the shape description of an object. When combined with dimensions, multiview drawings serve as the main form of communication between designers and manufacturers.

All three-dimensional objects have width , height , and depth .

Width is associated with an object's side-to-side dimension.

Height is the measure of an object from top-to-bottom .

Depth is associated with front-to-back distance.

Orthographic projection is a technique that is used to create multiview drawings.

Orthographic projection is any projection of the features of an object onto an imaginary plane of projection. The projection of the features of the object is made by lines of sight that are perpendicular to the plane of projection.

A projection plane , also referred to as a plane of projection or picture plane , is an imaginary surface that exists between the viewer and the object.

The projection plane is the surface onto which a two-dimensional view of a three-dimensional object is projected and created.

Projection lines are used to project each corner outward until they reach the projection plane .

A projection line is an imaginary line that is used to locate or project the corners, edges, and features of a three-dimensional object onto an imaginary two-dimensional surface.

Given the overall dimensions of the object, a pencil, and a sheet of graph paper, a sketching M ultiview drawing can be easily done using points, construction lines, and object lines.

Step #1 : Calculate the amount of space that the views will take up.

Step #2 : Layout the boxes within which the individual views will occur using points and construction lines.

Step #3 : Identify the visible edges by drawing object lines on top of the construction lines.

Assignment: Create a Multiview drawing of each of the objects pictured below. What do you notice about each object?

Isometric Projection

The representation of the object in figure 2 is called an isometric drawing. This is one of a family of three-dimensional views called pictorial drawings. In an isometric drawing, the object's vertical lines are drawn vertically, and the horizontal lines in the width and depth planes are shown at 30 degrees to the horizontal. When drawn under these guidelines, the lines parallel to these three axes are at their true (scale) lengths. Lines that are not parallel to these axes will not be of their true length.

Figure 2 - An Isometric Drawing

Any engineering drawing should show everything: a complete understanding of the object should be possible from the drawing. If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. One can pack a great deal of information into an isometric drawing. However, if the object in figure 2 had a hole on the back side, it would not be visible using a single isometric drawing. In order to get a more complete view of the object, an orthographic projection may be used.

Assignment: Follow the tutorial below to create the sketch as pictured in the tutorial. Then, choose an object of your own to project isometrically.

YouTube Video

One and Two Point Perspective

A drawing has one-point perspective when it contains only one vanishing point on the horizon line. This type of perspective is typically used for images of roads, railway tracks, hallways, or buildings viewed so that the front is directly facing the viewer. Any objects that are made up of lines either directly parallel with the viewer's line of sight or directly perpendicular (the railroad slats) can be represented with one-point perspective. These parallel lines converge at the vanishing point.

One-point perspective exists when the painting plate (also known as the picture plane) is parallel to two axes of a rectilinear (or Cartesian) scene – a scene which is composed entirely of linear elements that intersect only at right angles. If one axis is parallel with the picture plane, then all elements are either parallel to the painting plate (either horizontally or vertically) or perpendicular to it. All elements that are parallel to the painting plate are drawn as parallel lines. All elements that are perpendicular to the painting plate converge at a single point (a vanishing point) on the horizon.

File:Perspectivephoto.jpg File:One point perspective.jpg File:Inside Greenwich Foot Tunnel.jpg

A drawing has two-point perspective when it contains two vanishing points on the horizon line. In an illustration, these vanishing points can be placed arbitrarily along the horizon. Two-point perspective can be used to draw the same objects as one-point perspective, rotated: looking at the corner of a house, or looking at two forked roads shrink into the distance, for example. One point represents one set of parallel lines, the other point represents the other. Looking at a house from the corner, one wall would recede towards one vanishing point, the other wall would recede towards the opposite vanishing point.

Two-point perspective exists when the painting plate is parallel to a Cartesian scene in one axis (usually the z-axis) but not to the other two axes. If the scene being viewed consists solely of a cylinder sitting on a horizontal plane, no difference exists in the image of the cylinder between a one-point and two-point perspective.

Two-point perspective has one set of lines parallel to the picture plane and two sets oblique to it. Parallel lines oblique to the picture plane converge to a vanishing point,which means that this set-up will require two vanishing points.

Assignment: Follow the tutorial below to create the sketch as pictured in the tutorial. Then, choose an object of your own to project in two point perspective.

YouTube Video