Isometric view and its projections
As per the topic, isometric view and it's projections
The definition of an isometric view:
Grab any object in front of you. A pencil, remote control, computer mouse, bobble-head doll, coffee cup, etc. Look at it. Now turn it upside down, unless it's full of your favorite beverage! Turn it around. Turn it sideways. Each time you move it you're looking at a different view of that object. You can see depth and edges. You can tell that it's not just a picture, but a real thing. Your eyes give you many clues to the objects in your world that are three-dimensional.
A piece of paper has only two dimensions; it's flat. If you try to draw an object on a piece of paper, you'll notice that it's not easy to make the drawn object look like it has depth. One way is to use an isometric view, which is derived from the Greek words iso, meaning equal, and metric, meaning measurement. When using an isometric view, you line up the drawing along three axes that are separated by 120-degree angles from each other. The three axes, or visible or invisible guidelines that establish directions for measurement, extend all the way to the edge of the paper or screen in both directions, forming 60-degree angles between the axes. Many of the lines in an isometric drawing will be parallel to one of the axes. Generally, every right angle on an isometric drawing will line up with at least two of the three axes.
Here's an important rule regarding isometric drawings: Every measurement on a line parallel to an axis will be correct. It will be either be the same length on the drawing as it is on the object, or it will be drawn exactly to scale, like the scale on a map or a model airplane. Every line that is not parallel to one of the axes will not be drawn to measurement or to scale. You can see how that works in the following example.
Projections: It is of four types 1st angle projection, 2nd angle projection, 3rd angle projection and 4th angle projection. Generally we use only 1st angle projection and 3rd angle projection.
1st angle projection:
In first-angle projection, the object is conceptually located in quadrant I, i.e. it floats above and before the viewing planes, the planes are opaque, and each view is pushed through the object onto the plane furthest from it. Extending to the 6-sided box, each view of the object is projected in the direction (sense) of sight of the object, onto the (opaque) interior walls of the box; that is, each view of the object is drawn on the opposite side of the box. A two-dimensional representation of the object is then created by "unfolding" the box, to view all of the interior walls. This produces two plans and four elevations. A simpler way to visualize this is to place the object on top of an upside-down bowl. Sliding the object down the right edge of the bowl reveals the right side view.
3rd angle projection:
In third-angle projection, the object is conceptually located in quadrant III, i.e. it is positioned below and behind the viewing planes, the planes are transparent, and each view is pulled onto the plane closest to it. Using the 6-sided viewing box, each view of the object is projected opposite to the direction (sense) of sight, onto the (transparent) exterior walls of the box; that is, each view of the object is drawn on the same side of the box. The box is then unfolded to view all of its exterior walls. A simpler way to visualize this is to place the object in the bottom of a bowl. Sliding the object up the right edge of the bowl reveals the right side view.
Now you can make an isometric view and it's projections of any object.