virtual reality lighting
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Public lighting systems have evolved to meet the demanding requirements of smart cities, becoming smart systems themselves. It’s a new dawn for this basic municipal service, which has undergone a transition from a simple method of illuminating spaces to smart and sensor-enabled systems.

The article first appeared in ESI Africa Issue 4-2020.
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Technical aspects are no longer the focus in the conversion process of transforming a city into a smart city but rather the city users’ satisfaction, together with additional factors such as sustainability, quality of life, urbanisation, and smartness.

Facilitating this shift is the availability of more efficient and flexible light sources (in particular light-emitting diodes – LEDs), as well as innovative and more cost-effective control and communication systems.

Smart design for lighting systems

With the new and improved lighting systems, designers now need to use methodologies and parameters to evaluate the smartness of these systems. Traditional methodologies based on objective parameters, such as photometric units, need to be combined with those based on subjective parameters (visual performance, perception and emotions) in order to meet people’s expectations.

Three main lighting systems applications for which a smart design is required include road lighting, green area lighting, and architectural lighting.

Road lighting

To light a road means taking into account different visual tasks (recognising vehicles, people, objects, or signals) and typologies of users (drivers, cyclists, and pedestrians), which can be a significant challenge for lighting designers. For these reasons, standards and laws are issued by the city administrators to define specific objective requirements, generally based on the minimum values of photometric requirements that the road lighting systems have to guarantee.

Illuminance and luminance levels can be considered the most used control parameters. The following additional subjective parameters in the design and siting of road lighting installations and equipment should be considered:

• choice of supporting method; for example, columns with or without brackets, suspension wires, or direct mounting on buildings;

• scale and height of lighting columns or other suspension elements in relation to the height of adjacent buildings, trees, and other salient objects in the field of view;

• mounting height of the luminaire; and

• the lit appearance of the complete installation.

Green area lighting

The various activities that people can do in green areas (running, cycling etc.), as well as the presence of vegetation and animals, make the lighting design of these areas particularly complex. For these reasons, basing the green areas lighting design only on the photometric requirements may not be the optimal design approach.

Many studies agree that a successful green area lighting design is achieved mainly using a hierarchical approach to choose light types and intensity. For a park, the choice of the correlated colour temperature (CCT) of light is a particularly important issue. CCT affects not only the human perception of the environment and safety but also the animals.

Additional issues to take into account in parks lighting design are:

• the position of luminaires;
• the mounting height of the luminaire;
• the choice of luminaire; and
• the luminaire supporting pole.

Architectural lighting

In recent years, architectural lighting has evolved from a static instrument to light façades as a means of communication. Smart cities have increasingly encouraged human-computer interaction with a range of cutting-edge technologies. These days, smart media displays/façades provide a new means of communication and creative engagement in smart cities

Due to the growing complexity of lighting design, field trials, that use real lighting equipment, can no longer be used. The design of complex lighting systems needs the use of smart simulation software that can provide a realistic virtual representation of the final results. Artificial lighting plays a relevant role in people’s perceptions of buildings and cities since it can be used for both functional and aesthetic reasons.

The CCT of the emitted light can be used in architectural lighting for different purposes. The light CCT can be used to align a building with or differentiate it from its surroundings by using light with a similar or different CCT to that used for the external lighting. The light CCT can also be chosen to accentuate the building materials.

Use of virtual reality for lighting design

The use of immersive virtual reality (IVR) as a tool for lighting design is a topic that is drawing great interest in the scientific community. IVR allows the designer to overcome some barriers in carrying out tests in real environments, such as to control the luminous conditions, to change the visual conditions and safely investigate hazardous environments.

Key factors in using virtual reality environments as substitutes for real ones are their ability to reproduce a light environment perceived as the real thing, a correct light distribution from the photometrical point of view, and the perceptions that people experience in real spaces.

Several reviews allow the identification of some preliminary information useful when researching the ability of virtual reality (VR) systems to reproduce precisely the physical behaviour of light in outdoor virtual environments:

• calibrated 360 degree HDR images can be used to reproduce a correct light distribution;

• game engines can be used for correct reproduction of light distribution;

• head-mounted displays (HMDs) are the best VR equipment for an exact perception of light distribution;

• game engines do not allow a direct evaluation of illuminance and luminance values; and

• in VR a correct light distribution can provide an adequate level of space presence, lighting appearance and environment perception.

In conclusion, researchers agree on considering virtual reality, especially coupled with HMDs, to be a promising methodology for investigating people’s visual perception thanks to its ability to reproduce the real world. IVR can be used to identify the optimal lighting design solution that is able to assess both energy savings and people’s acceptance. ESI

Acknowledgement
This article is based on an adaption of a 2020 paper titled Virtual Reality for Smart Urban Lighting Design: Review, Applications and Opportunities, written by Michelangelo Scorpio, Roberta Laffi, Massimiliano Masullo, Giovanni Ciampi, Antonio Rosato, Luigi Maffei, and Sergio Sibilio – of the University of Campania Luigi Vanvitelli.

View the full list of references and diagrams. www.researchgate.net/publication/343204920