[Maths Class Notes] on Oblique Sketch Pdf for Exam

What is Oblique Sketch?

Oblique sketch is an easy and efficient technique of representing an object in pictorial form. Generally, the circles and angles parallel to the plane of projection are considered to be the true size and shape of the object while constructing oblique sketches. This is because they can be easily reflected. Circular faces on the top or sides of the oblique plane appear to be elliptical. So, the sketches are drawn in such a way that almost all the circular faces are in the front view. Oblique sketching is one of the most advanced techniques in digital marketing and e-commerce businesses where advertising a product along with its features is of utmost importance. 

What is Oblique Sketch Definition:

Oblique sketch definition states that it is a method of representing a three-dimensional object with a three-dimensional view on a two-dimensional plane surface. A number of 3-dimensional objects are visible in and around the surroundings that include a cylinder, cube, cuboid, cone, sphere, etc. All these are three-dimensional objects. However, the representation of these objects on a paper with all their three dimensions needs some kind of sketching techniques, one of which is an oblique drawing. 

Types of Oblique Drawing:

There are three types of oblique drawing. They are:

1. Cavalier oblique drawing

2. Cabinet oblique drawing

3. Normal oblique drawing

• In cavalier oblique drawing, the two dimensions are represented on horizontal and vertical axes. The third dimension is represented on the axis at an angle 450 to two dimensions. 

• In cabinet drawing, the dimensions of length and width are represented by two perpendicular axes. The third dimension (depth) is represented by an axis which is at 300 or 600 to the horizontal axis. 

The below figure depicts the two different kinds of oblique sketch of cuboid.

Oblique Sketches Advantages:

• The types of oblique drawing represent the exact shape and size of one of the faces of the object. It is good for elliptical shapes and axonometric projections representation. 

• Sizes can be compared easily because of the absence of perspective foreshortening. 

• It gives a three-dimensional view of a few objects but not all. 

• Though the view is perfect and precise, it gives a distorted look to the object if the plane of projection is not positioned appropriately.

• It does not give a realistic look because of the lack of foreshortening. 

The difference between isometric and oblique drawing is stated in the table below.

Difference Between Isometric and Oblique Drawing:

The figure shows the isometric and oblique sketch of cuboid.

How to Construct an Oblique Sketch?

Oblique sketch depicts the perspective of any object in three dimensions. An example of representing a 4 x 4 x 4 cube (Oblique sketch of cuboid or cube) is explained below. 

Step 1:

A squared paper with a minimum of 25 squares is to be taken. 

Step 2:

One of the front faces of the 4 x 4 cube, i.e. a 4 x 4 square is sketched on the paper. 

Step 3: 

The face behind the front face is sketched one row and one column ahead of the front face as shown in the figure.

Step 4:

The corresponding edges are joined with straight lines. 

Step 5:

The edges of the hidden surfaces are replaced by dotted lines. 

Fun Facts:

1. In oblique drawings, the choice of front surface parallel to the plane of projection is very important. For example, any face of a cube can be chosen as a front surface. However, if one of the faces has a hole in it, then the face with hole is preferred to be taken as a front surface to give a proper 3-dimensional view.

2. In cabinet drawing, the proportional scale of the axes is 1 : 1 : ½ and that in cavalier drawing is 1 : 1 : 1.