How to Draw Oblique Sketches Easily for Accurate Geometry
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.
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Types of Oblique Drawing:
There are three types of oblique drawing. They are:
Cavalier oblique drawing
Cabinet oblique drawing
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.
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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:
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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.
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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.
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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.
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Step 4:
The corresponding edges are joined with straight lines.
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Step 5:
The edges of the hidden surfaces are replaced by dotted lines.
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Fun Facts:
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.
In cabinet drawing, the proportional scale of the axes is 1 : 1 : ½ and that in cavalier drawing is 1 : 1 : 1.
FAQs on Oblique Sketch: Definition, Steps & Uses
1. What is an oblique sketch in mathematics?
An oblique sketch is a type of 2D drawing used to represent a 3D object. In this method, the front face of the object is drawn to its true shape and size, while the receding lines that create the sense of depth are typically drawn at a 45° angle. This technique provides a quick, three-dimensional view of an object without the complexity of perspective drawing.
2. What are the main steps to draw an oblique sketch of a cube?
To draw an oblique sketch of a cube, you can follow these simple steps:
Step 1: Start by drawing the front face of the cube, which is a square, to its correct dimensions.
Step 2: From each of the four corners (vertices) of the square, draw parallel lines extending backwards at a 45° angle. These are the receding lines and represent the depth of the cube.
Step 3: Connect the endpoints of these receding lines to form the back face of the cube. This back square will be identical in size to the front one.
Step 4: You can make the hidden edges as dashed lines to complete the sketch and show that it is a solid object.
3. How is an oblique sketch different from an isometric sketch?
The primary difference between an oblique and an isometric sketch lies in their orientation and realism.
Angle of Projection: In an oblique sketch, the front face is drawn flat, and depth is shown with receding lines at a 45° angle. In an isometric sketch, the object is rotated, and all axes are drawn at 120° to each other, with vertical lines remaining vertical.
Realism: Isometric drawings provide a more realistic, 3D view of an object because all dimensions are drawn to scale. Oblique sketches can appear distorted, as the receding sides are not foreshortened accurately.
Front Face: The front face of an oblique sketch is true to shape, while in an isometric sketch, no face is shown as a true shape.
4. What is the main limitation of using an oblique sketch?
The main limitation of an oblique sketch is its lack of realism and potential for visual distortion. Because the receding lines are drawn at a fixed angle (usually 45°) and are often not shortened to reflect perspective, the object can look unnaturally long or out of proportion. This makes oblique sketches less suitable for technical or engineering purposes where dimensional accuracy from all viewpoints is critical.
5. What are the practical uses of oblique sketches?
Oblique sketches are most useful for creating quick, easy-to-draw pictorial representations of objects, especially in the early stages of design. Their primary applications include:
Furniture Design: To quickly show the design of a cabinet or a desk where the front view is most important.
Architecture: For simple illustrations of building layouts or interior room designs.
Educational Purposes: To help students visualise 3D shapes easily without learning complex drawing rules.
6. Are there different types of oblique sketches?
Yes, the two main types of oblique sketches are based on how the depth is scaled:
Cavalier Projection: In this type, the receding lines are drawn to their true length. This makes the object look deeper and more distorted than it actually is.
Cabinet Projection: In this more realistic type, the length of the receding lines is halved. This foreshortening reduces distortion and makes the object appear more proportional and visually pleasing.
7. Why is a 45-degree angle commonly used for the receding lines in an oblique sketch?
A 45-degree angle is commonly used for receding lines in an oblique sketch primarily for simplicity and convenience. It is easy to estimate and draw using standard drafting tools like a set square. This angle provides a clear sense of depth without overcomplicating the drawing process, making it an ideal choice for quick, illustrative purposes where precision is not the main goal.
