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The term three-dimensional is general. It describes an object; room or building that is drawn in a manner that allows the eye to interpret it as a real element.
The images are hand drawn, as in sketches and artistic renderings, or created with a computer program. It is a communication method of visually presenting the spatial relationship of an object, room or building on a flat plane. The flat plane is this case is a sheet of paper or a computer screen.
A three-dimensional (3D) drawing shows the three values, length, width and height. A two-dimensional drawing (2D) only provides two dimensions, length and width or width and height.
There are many types of three-dimensional drawing techniques. Some common methods are perspectives, isometric and plan oblique.
Perspectives
A perspective is the most realistic three-dimensional representation of objects or spaces.
Items are drawn in a way that is similar to how the human eye perceives them.
Objects within a space appear smaller as they get further away.
Horizontal lines look non-parallel. They appear to converge at an imaginary point in the distance.
Many photographs in magazines illustrate this concept.
Extend the lines at the edge of the furniture or ceilings on a photograph in a magazine.
The lines appear to vanish to one or two points depending on the angle of the picture.
Drawing perspectives takes training and practice.
A little artistic skill is necessary to make adjustments to create a truly realistic view.
A professional presentation involves adding color and shading.
A design and plan view is established before beginning a perspective drawing.
The plan is used to determine the angle of the view as well as the size of the final image.
The following is a very basic explanation of one-point and two-point perspective drawing.
Both types involve establishing a horizon line.
This imaginary horizontal line represents where the earth meets the sky.
Vanishing points are added to this horizon line. A vanishing point, also imaginary, is the point to which the horizontal edges of all objects will meet. All vertical edges of objects remain vertical.
A one-point perspective is created when only one vanishing point is positioned on the horizon line. A two-point perspective uses two vanishing points positioned on the horizon line.
Vanishing points placed too close together produce a distorted view.
The horizon line and vanishing points are only used for blocking in objects in a room or the elements of an exterior view of a building. They do not appear on the finished drawing.
The view of an object changes when positioned above, on or below a horizon line.
Above tends to show the underside. On the horizon line presents an eye-level view. Below shows the top. It is similar to the way the human eye sees objects based on where a person is positioned in relationship to them.
It is important to consider this when planning an image of a room or building. For example, it is realistic to draw a building on the horizon line with the top of it above the horizon line. It gives the impression of looking up at the building from street level.
The diagrams below provide a basic example of a cube in various positions in relationship to a horizon line.
Isometrics
An isometrics is another method used for presentation drawings.
The view is not as realistic as a perspective. However it is a quick and easy means of conveying an idea.
They are most commonly used to explain the design concept for objects, such as millwork, furniture or fixtures. In some cases, they are also a quick method for showing the design of a room interior or a building.
An isometric is a view of an object where the horizontal lines are at an equal angle.
The horizontal lines represent the length and width. Both are at the same angle, which is typically 30 degrees. Vertical lines represent the height. Vertical lines are always vertical, unless the object itself has angled edges.
All lines used to drawn the details of the object are kept parallel to each other. In other words all lines representing a height are parallel to each other, whether they are at the front edge, middle or back edge of the item. All lines representing a length are parallel to each other, whether they are at the top or middle of the object. The same applies to the width.
Using a set scale to draw the image keeps it in proportion.
Measurements along the vertical and angled horizontal lines are at the same scale.
For example, a scale of 3/ 4” = 1’-0” is used to create the height, length and width as they apply to the specific object.
With practice it becomes second nature to do free-hand sketches using the above principals.
It is a quick and easy method to explore different ideas before reaching a final design concept.
An example of an isometric is provided under the heading at the bottom of the page.
Plan Oblique
A plan oblique is a three-dimensional representation of a room or space. The view is one of looking down into the area. It is necessary to have a design concept and floor plan established.
The floor plan is a two-dimensional view. It provides the length and width of walls in the space.
It shows length and width of all objects within it, such as furniture, counters and cabinets.
The floor plan is drawn to scale. An example of a scale is 1/ 4” =1’-0”.
The plan is rotated to suit a desired view. A common rotation angle is 60/ 30 degrees.
Vertical lines are projected from points on the plan to provide the height of the walls and objects.
To avoid a distorted appearance the vertical lines are normally drawn at a portion of the scale of the plan. Vertical lines are usually at a half to a third of the scale used for the plan.
A plan oblique provides a visual means of understanding the layout of the objects within the space. With the addition of details to each object the design concept is easily interpreted.
Dimensions, such as length and width are often applied to the drawing as it is drawn to scale.
In some cases, a wall or portion of a wall is eliminated to provide a better view of certain design details that the wall will block when included.
An example of a plan oblique is provided under the heading at the bottom of this page.
Designers and architects frequently use three-dimensional drawing for professional presentations. Whether it is a perspective, isometric or plan oblique, it is produced with accuracy. Computer programs create such realistic perspective views they are easily mistaken for actual photographs. Hand drawn views have an artistic quality while still providing an accurate interpretation. Clients and do-it-your-self persons will often draw their own rough three-dimensional sketches.
It is a communication method that anyone can use. It can express a design idea better than words.
To view a basic example of the different types of three-dimensional drawings, click on the heading below.
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Three-Dimensional Drawings
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