The user interface (UI), in the industrial design field of human–computer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators’ decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.

Generally, the goal of user interface design is to produce a user interface which makes it easy, efficient, and enjoyable (user-friendly) to operate a machine in the way which produces the desired result. This generally means that the operator needs to provide minimal input to achieve the desired output, and also that the machine minimizes undesired outputs to the human.

User interfaces are composed of one or more layers including a human-machine interface (HMI) interfaces machines with physical input hardware such a keyboards, mice, game pads and output hardware such as computer monitors, speakers, and printers. A device that implements a HMI is called a human interface device (HID). Other terms for human-machine interfaces are man–machine interface (MMI) and when the machine in question is a computer human–computer interface. Additional UI layers may interact with one or more human sense, including: tactile UI (touch), visual UI (sight), auditory UI (sound), olfactory UI (smell), equilibrial UI (balance), and gustatory UI (taste).

Composite user interfaces (CUI) are UIs that interact with two or more senses. The most common CUI is a graphical user interface (GUI), which is composed of a tactile UI and a visual UI capable of displaying graphics. When sound is added to a GUI it becomes a multimedia user interface (MUI). There are three broad categories of CUI: standard, virtual and augmented. Standard composite user interfaces use standard human interface devices like keyboards, mice, and computer monitors. When the CUI blocks out the real world to create a virtual reality, the CUI is virtual and uses a virtual reality interface. When the CUI does not block out the real world and creates augmented reality, the CUI is augmented and uses an augmented reality interface. When a UI interacts with all human senses, it is called a qualia interface, named after the theory of qualia. CUI may also be classified by how many senses they interact with as either an X-sense virtual reality interface or X-sense augmented reality interface, where X is the number of senses interfaced with. For example, a Smell-O-Vision is a 3-sense (3S) Standard CUI with visual display, sound and smells; when virtual reality interfaces interface with smells and touch it is said to be a 4-sense (4S) virtual reality interface; and when augmented reality interfaces interface with smells and touch it is said to be a 4-sense (4S) augmented reality interface.

Use of 3D modeling in BAS GUI has changed the way we design; for the better. Not only does 3D modeling help the BAS operator and end users visualize building requirements, but also improves monitoring efficiency and accuracy.

3D modeling for BAS allows the operator to see what they would not see when viewing in 2D. It gives the operator the ability to physically see how much real estate an object takes from all perspectives. When designing in 2D, the designer needs to create a separate plan and elevation view to see the space requirements of an object, which takes longer to do.
When designing in 3D, the design is done in one model. Whereas when a design is done in 2D, it is typically done in multiple models, one for each view. By doing a design in multiple models it creates an atmosphere where more mistakes can occur by having information duplicated. When a design is done in 3D, it assists designers with coordination. The designer can walk through a 3D model with specialized software and see the actual size and space of the design. It also allows the designer to see if their designs conflict with other disciplines or existing conditions they may not readily see in 2D. The 3D walkthrough software also allows the designer to run interference checks to see if the design clashes with other items in the 3D model. By using the 3D walkthrough software, the designer can easily see whether the design allows for equipment maintenance access and operational access, and addresses safety concerns. This allows the designer to create a more user-friendly design for the end user.

By designing in 3D, the designer can also review a design using the 3D walkthrough software with the end user. This is particularly helpful for end users who have a hard time visualizing designs from 2D drawings. This allows them to see how much clearance and access they will have around a design before it is physically built.
The advantages of 3D modeling for designers is not limited to productivity and coordination, it is an excellent communication tool for both the designer and end user. 3D models can help spark important conversations during the design phase and potentially avoid costly construction mishaps.