Daylighting Design Optimization using Rhinoceros and Grasshopper Plug-in: The High Museum of Art (HMA) Expansion Case Study

Nowadays, computational techniques offer a more convenient design process. They help realise complex designs and open new solutions possibilities. This report uses case study methodologies to examine the benefits and challenges of computational design approaches, specifically parametric design, in The High Museum of Art (HMA) expansion project. Moreover, comparing two previous studies offering different approaches to evaluating skylight performance indicates that parametric design allows iterative scenarios to optimise the skylight system and enhance creativity. The tools and workflow of the parametric method show that it can be used as seeds for future projects. However, several challenges emerge, which include the difficulties of interpreting the designer’s idea into a programming language and concerns about the idealism of an architect that will be driven only by the algorithm rather than building objectives and clients' requirements. Constant learning and evaluation of the ideal design process are suggested as solutions to overcome the issues mentioned in the report.

1. Introduction

Nowadays, the internet and information systems are growing rapidly. Digital technology provides an abundant amount of data at our fingertips. In respon, all industries, including Architecture, Engineering, and Construction (AEC), are shifting accordingly. For example, numerous computer software and platforms are now available to help the design process run efficiently and collaboratively.

Conventional design approaches, both paper-based and computer-aided design (CAD), usually include analysing the site, conceptualising, and developing the design. This process can be said to be linear, although it is generally evaluated back and forth to alter the solution (U. Toker, 2022). Still, the concept can not be established without manually adding or erasing the geometry. Conversely, the evolution of computational design approaches offers a more dynamic and non-linear way of thinking, namely, Digital fabrication, Parametric Design, Gamified Exploration, and the application of Artificial Intelligence. These methods allow the geometric to be explored and refined at any stage of the design process. Hence, it can enhance creativity as well as offer better design solutions. However, the development of computer process design and advanced technologies also demands an adaptation of the role of architects and engineers.

This report aims to examine the application of the computational design approach, particularly the parametric method, in the case of the High Museum Atlanta (HMA) expansion project. However, the implementation of parametric design in the actual project was unknown. Therefore, two previous studies were taken to compare the performance of the skylight design using two different methodologies: the censors method and parametric modelling. Furthermore, tools and the workflow associated with the parametric design will be explained.

2. Literature Review

2.1. Computational Design Parametric Technology

Before the emergence of computational design technology, designer sketched their ideas onto paper. When Computer-Aided Design (CAD) was introduced, an experiment of a previous study suggested that it helps reduce time and verify the accuracy of the design ideas (N. Cross, 2006). This computer ability then evolved into a tool for three-dimensional visualisations in post-2000 and has been developed toward digital generative and performance-based approaches. Generative design creates a range of generated design options where the designer makes the code, whilst performative focuses on the simulation of the design performance using various analysis (R. Oxman, 2017). Both employ a parametric solution where the designer specifies the relation between the input and the expected output (U. Toker, 2022).

Parametric modelling software generally comprises two interfaces: modelling and programming interfaces. It requires two programs to connect the visualisation and the commands.

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Figure 1. Example of Parametric Windows. Left: Grasshopper’s Canvas and Rhinoceros Interfaces; Right: a Basic Geometric Input and Component in Grasshopper (U. Toker, 2022)

Figure 1 illustrates the relationship between the modelling visualisation tool, a Rhinoceros, and a Grasshopper’s scripting window. For instance, geometry is created in the Rhinoceros and brought onto the Grasshopper canvas. Once these two entities are interconnected, the editing feature can be executed in the programming interface because the visualisation from the Rhinoceros is now embedded with a certain set of rules in the Grasshopper. However, the correlation can be cancelled (U. Toker, 2022).

Table 1. Example of Parametric Design Software

No	Geometric Visualization	Parametric Interface	Developer	Sources
1	Rhinoceros	Grasshopper	Robert McNeel & Associates	G. Celani et al (2012)
2	Revit	Dynamo	Autodesk	S. Kardogan et al (2024)
3	ArchiCAD	Param-O	Graphisoft	S. Kardogan et al (2024)
4	MicroStation	Generative Components	Bentley	G. Celani et al (2012)

Rhinoceros and Grasshopper are registered as Robert McNeel and Associates’ trademarks (U. Toker, 2022). Rhinoceros has many plugins for geometric and performance analyses, such as structural or energy consumption. “A Rhino plugin is a software module that extends the functionality of Rhino or Grasshopper by adding commands, features, or capabilities” (D. Rigdon-Bel, 2021).

Table 2. Examples of Plugins Compatible with Grasshopper

No	Plugins	Function	Sources
1.	Ladybug	Bridging the EnergyPlus Weather files (.EPX) to Grasshopper and illustrating the 2D and 3D simulation.	S.R. Mostapha et al (2013)
2.	Honeybee	Perform analysis by allowing users to modify the radiance, daysim and energy plus.
3.	Butterfly	Facilitate Computational Fluid Dynamics (CFD) simulation using OpenFOAM.
4.	Octopus	Set up and run multiple objective optimation algorithms.
5.	Karamba	Perform structural analysis, such as load calculation.	N. Mohol et al (2023)
6.	Follogram	Allows viewing and sharing of mixed-reality models and the environment.	O. Kontovourkis et al (2023)
7.	Wasp	Conduct the phyton algorithm to models.	A.Agkathidis et al (2023)
8.	Robots	Robots is a plugin for Rhino's Grasshopper visual programming interface. It allows you to create and simulate robot programs.	Visose et al (2024)
9.	Galapagos	Single-objective optimisation tool by providing generating the algorithm.	K. Lie et al (2023)

2.2. Museum dan Lighting Standard

Museums are a place to preserve and exhibit collections. It also functions for research, educational, and recreational purposes (C.-W. Sheng et al., 2012). The collection of museums generally is the historic artefacts which have prominent cultural and heritage benefits for humanity (P. Barron et al., 2017). It includes relics of nature, art collections, and technological innovation. Moreover, in modern museums, various activities are now available, not only to enjoy the display but also to engage with interactive classes or forums.

A lighting system in a museum is essential. It can determine how the showcase performs and preserves. Both natural and artificial lights can influence visitors’ perception and experience of the exhibitions. According to Stach (2021), a good museum’s lighting considered several criteria as follows : (1) a decent degree of illumination, (2) a balance of brightness distribution, (3) Direct glare and reflection prevention, (4) direction of the light to enhance the shape of the display, (5) light colour and rendering and (6) light levels and colour temperature.

There are many indicators to measure the effectiveness of daylighting. However, Annual Cumulative Illuminance (ACI) and Useful Daylight Illuminance (UDI) are two indicators used for this study. ACI is the total illuminance received in a particular place for a year (K. Li et al., 2024), whereas UDI is the percentage of the useful illuminance that drops onto the floor and wall annually. For medium sensitivity art collection, the ideal ACI is between 50,000-480,000 lux/year, while UDI is 50% minimum for the 50-200 lux illuminance (E. Stach, 2021).

Typically, natural daylight and artificial lighting are combined to create sufficient light. Nonetheless, excessive artificial lighting can cause environmental issues if the energy source is still fossil fuel-based. Consequently, managing natural daylighting should be prioritised. Previous studies have categorised several types of skylights. The following picture shows a previous study that demonstrated three types of skylights: surface, linear, and point system.

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Figure 2. Three Types of Natural Daylighting System (K. Li et al., 2024)

3. Case Study

3.1. The HMA Overview

The HMA opened for the first time in 1983. Initially, it only had 134.000 square feet of museum-built space. However, from 1999 to 2005, the expansion project was completed under Renzo Piano's design, and 177,000 square feet were added to the existing museum (P. Zamani et al., 2010). It is located in Atlanta, USA, and has more than 17,000 works of art from the 19^th - 20^th century from decorative to contemporary art and painting (E. Stach, 2021). Situated inside the Atlanta College of Art, it is bordered by Fifteenth and Sixteenth Street on the west-east side. Combined with the concert and theatre hall in the complex, the HMA become the largest art museum in the United States southeast (R. Piano et al., 2018).

Figure 3. Yellow Shading Illustrates the Expansion (R. Ryan, 2006)

A large white building with a lawn with High Museum of Art in the background

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Figure 4. View of The HMA, Courtesy of the HMA (J. Forbes, 2024)

The expansion encompasses three new blocks: the Wieland Pavilion, the Anne Cox Chambers Wing, and the Administrative Service Center. They are built around a public square containing a new restaurant, cafes, bookshops, and offices. The Wieland Pavillion and the Anne Cox Chambers Wing are the two new buildings that host most of the art collections in the latest expansion (L. Piano, 2011). Connected by a glass bridge, these two new buildings feature a high ceiling to display large art pieces (J. H. M. D. T. Hursley, 2024).

The design team comes from a broad range of experts. The design team at Renzo Piano Building Workshop (RPBW) architecture firm is famous for its museum portfolios, which are sensitive to natural light details (E. Stach, 2021). In collaboration with Lord, Aeck & Sarfent Inc. as Architect, the consultants include Ove Arup & Partner, Uzun & Case, Jordan & Skala as structure and service; Arup Acoustics; Arup Lighting; HDR/WLJorden in civil engineering; Jordan Jones and Goulding in landscaping, Bergmeter Associate for the interior/restaurant; and Brand, Allen Architect in the interior/retail (L. Piano, 2011).

3.2. Natural Lighting Optimization

The HMA preserves prominent arts and historical collections. The focus of the lighting design in the Wieland Pavillion and the Anne Cox Chambers Wing is to guarantee the visitor experience when viewing the artwork as well as to protect the showcase from damaging factors, such as direct sunlight. Hence, designing the lighting is crucial. Unlike artificial lighting, natural daylighting also plays a significant effect in energy conservation and reduces operational costs (K. Li et al., 2024).

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Figure 5. Aerial View of the HMA building, Courtesy of Denance, Michel (L. Piano, 2011)

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Figure 6. The Anne Cox Chambers Wing North View, Courtesy of Denance, Michel (L. Piano, 2011)

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Figure 7. Section from Fifteenth to Sixteenth Street (L. Piano, 2011)

The RPBW’s considerations in a building's natural lighting performance included material and immaterial characteristics. The material factor includes durability, whilst the immaterial entails the visual and spatial characteristics of the material, such as transparency, lightness, and the vibration of light in architecture. The design team experimented with techniques and scientific aspects of lighting using different shapes and shading systems. In the HMA, RPBW created 1.000 units of passive skylight made from a combination of Glass Fibre-Reinforces Gypsum (GFRG) and aluminium. This spoon-shaped skylight was distributed on top of the upper floor of the Wieland Pavillion and the Anne Cox, lined through a grid ceiling to reflect indirect sunlight (E. Stach, 2021). The roof consists of modular aluminium panels. It acted as a shield to shade the skylight from intense sun rays, particularly the roof, due to the north (L. Piano, 2011). The interior’s material choices also enhanced the light ambience of the gallery by using coated natural oak flooring (K. Li et al., 2024) and a white ceiling that was closed at the bottom and perforated at the top (L. Piano, 2011). This combination of the material and the skylight lets the natural light illuminate the showcase nicely.

Figure 8. The Skyway Gallery in the Wieland Pavilion’s Upper Level, Courtesy of Denance, Michel (L. Piano, 2011)

Figure 10. Roof View, Courtesy of Denance, Michel (L. Piano, 2011)

Figure 9. Section of the Anne Cox Chambers Wing shows the extended aluminium facade shades some of the tubular skylight (E. Stach, 2021)

The skylight implemented a point system with exterior cone-shaped sunshades, circular glass skylights, and a light tube connected to the ceiling. It is a 1.82-meter tubular skylight, with 60 centimetres of it placed above the roof line. Each of the sunshades twists slightly to block the sun from the south and allows the soft northern daylight to bounce into the interior. There were two previous studies tested the performance of this system by using sensors and computational models. The first study was from Stach (2021), which put censors on the actual site, whereas the second one was from Li et al (2024), which utilised computational parametric simulation applied to a virtual model and tested on a physical model. These studies have parameters in common to test the correlation between the system and daylight performance. However, the computational parametric can offer more design options to achieve daylight system optimation. The diagram below illustrates the tools and workflow applied in the study.

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Figure 11. The HMA Expansion Project Research’s Tools and Workflow (K. Li et al., 2024)

Initially, the virtual 3D modelling was created using Rhinoceros. The geometry was then linked with the Grasshopper, so the model becomes adjustable in terms of the required dynamic parameters. Ladybug then provided EnergyPlus data from an open-source website (R. Grasshopper, 2018). This data functions as basic assumptions on the local weather conditions to conduct analysis and visualisation, such as sunlight hours and solar radiation (K. Liu et al., 2023). Ladybug and Honeybee were working concurrently to bridge environmental data provided by third parties. Besides EnergyPlus, there were also other providers, namely THERM, Radiance, OpenStudio and Daysim (R. P. Khidmat et al., 2022). Once the model was embedded with environment data and the command was set in the grasshopper canvas, the Octopus plugin generated the algorithm to reach an optimum daylighting design regarding its performance, cost and energy consumption (K. Li et al., 2024).

The parametric simulation showed 4987 scenarios after 29 times of iterations. The optimum ACI and UDI performance was achieved when the following dynamic criteria were met.


Figure 12. Left: Fix Parameters; Right: Dynamic Parameters (K. Li et al., 2024)

Table 3. Static and Dynamic Parameters in the Computational Research of the HMA Expansion’s Skylight System

Static Parameters	Dynamic Parameters
1. The design of the ceiling below skylights 2. The cone shape tubular medium between skylights and the ceiling	1. Height of the light well (a)	1.8 metres, between 0.7 and 0,6 metres above the roof line
	2. Sunshade angle against light well (b)	10^O-30^O
	3. The opening angle of the sunshade (c)	80^O-120^O
	4. The length of the sunshade (d)	1.3-1.5 metres
	5. The sunshade angle against the horizontal plane (e)	65^O-70^O
	6. The curvature of the sunshade (f)	-0.2-0.3 metres

4. Analysis and Discussion

The computational simulation, particularly the parametric method, was implemented in the HMA Expansion research. It explored different scenarios of dynamic parameters to formulate the best skylight design that demonstrated the ideal lighting performance. Two different methods had been used in the previous study. Nonetheless, the censor’s research method suggests that a series of computational models were needed to analyse the skylight roof system (E. Stach, 2021). The parametric approach, on the other hand, proposed myriad skylight design solutions.

Table 3. The Comparison of The HMA Skylight’s Previous Research

Aspect	Stach (2021)	Li et al (2024)
Aim of the Study	Verify the daylighting system on-site	Suggest the design of the skylight system to meet standards
Research Method	Censors on the actual site	Computational simulation tested on a model
Quantitative Threshold for Medium Sensitive Art Display
1. Useful Daylight Illuminance (UDI)	50-200 lux, persist minimum 50%/ year	50-200 lux, persist minimum 50%/ year
2. Annual Cumulative Illuminance (ACI)	Maximum 480,000 lux/ year	Maximum 480,000 lux/ year
Result
1. Useful Daylight Illuminance (UDI)	50-200 lux, persist 75%/ year	50-200 lux persist over 78.15%-80.61%/ year
2. Annual Cumulative Illuminance (ACI)	346,400 lux/ year	424,211 – 451,920 lux/ year
Dynamic Parameters
7. Height of the light well (a)	1.8 metres, 0.6 metres above the roof line	1.8 metres, between 0.7 and 0,6 metres above the roof line
8. Diameter of the Circular Glass	67 centimetres	-
9. Sunshade Angle against building axis	26^O -28.9^Ooff the building axis (facing north)	-
10. Sunshade angle against light well (b)	-	10^O-30^O
11. The opening angle of the sunshade (c)	93.8^O	80^O-120^O
12. The length of the sunshade (d)	1.43 metres	1.3-1.5 metres
13. The sunshade angle against the horizontal plane (e)	-	65^O-70^O
14. The curvature of the sunshade (f)	0	-0.2-0.3 metres

Table 3 compares two previous studies on the HMA skylight system. Both studies employed the ACI and the UDI threshold suggested by the Illuminating Engineering Society of North America (IESNA). IESNA recommended that the lighting system should consider the artefact's sensitivity to ensure the lighting will not damage it while still making it visible to the visitor. The results of these studies are slightly different. The first study explains that the optimal ACI and UDI are a minimum of 75% and a maximum of 346,400 lux/ year, respectively, whilst the second study demonstrates that the ACI ranges between 78.15% - 80.61%/ year and the UDI is 424,211 – 451,920 lux/ year. Regardless of the differences, the studies verified that the existing building has already met the IESNA standard requirement. The second study, however, can offer more comprehensive data by exploiting all daylighting system scenarios using parametric design tools. It stimulates the virtual models using parametric design tools which are Rhinoceros, Grasshopper, Ladybug, Honeybee, and Octopus. This process requires the designer to understand how to operate components in Grasshopper to make a logical rule and flow for their design.

The scenarios were generated from an algorithm in the models. A Grasshopper contributes a significant aspect to the process. It has key elements: (1) nodes, which are repositories of data that perform some function or command; (2) components, which are the nodes that perform logic. Every time the input changes, the component re-executed the output; (3) Sliders refer to the element of the component that allows the numerical range level; (4) Panel component, which fuctions to inspect the values of the input; (5) Wires serve as the node’s connection to define the flow of the rule (Rhinoceros3d, 2022).

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Figure 13. Example of the Relationship between Grasshoper’s Component within Environmental and Multi-Objective Optimization Plugin (R. P. Khidmat et al., 2020)

The evaluation and optimisation of the skylight system demonstrated that the ACI and the UDI could be tracked by parametric simulation. The process was generated automatically using a parametric algorithm based on the input to meet the expected output. However, the main weakness of the previous study was that they did not address the question of energy consumption and cost estimation in more detail. Even though the use of Octopus in this study aimed to find the optimum balance between those two aspects, the research would have been more relevant if a comparison between energy and operational costs had been explored.

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Figure 14. Left: Octopus’s Generation Outcomes Demonstrated All Iteration; Right: The Optimum UDI, DA (Daylight Anatomy) and ACI

Parametric design as a computational design approach can provide many alternatives during any stage in the design process once the models are embedded by the rule. Therefore, it can save time, help make rational decisions, and create complex designs. However, it has challenges, such as the difficulties of learning technical programming that is better aligned with the architects' roles (R. Yu et al., 2015). Consequently, it may seem intimidating for designers to elaborate on their ideas in a new language (U. Toker, 2022). Furthermore, the use of code-generated design can shift the design process by relying only on the algorithm rather than the project’s objectives. Nonetheless, it can be overcome by learning the virtual programming language to manipulate the object while still prioritising the client’s need.

5. Conclusion

The advantages of parametric design include opening many design alternatives using numerous performance analyses, such as structural and environmental aspects. It can also enhance creativity because of the automatisation and traceable iterative geometries creation. Furthermore, it can serve as a seed as the program is reusable. Despite the benefits, a challenge may emerge, for instance, the difficulty of translating the architect’s ideas into programming language and a possibility that the architect’s solution will be driven only by the algorithm rather than idealism, for example, aiming for the building objectives and the client’s requirements. (R. Yu et al., 2015). Building programming skills and emphasising the client’s requirements are recommended to overcome difficulties.

The HMA Expansion Case Study showed that a Parametric Design approach can be applied to evaluate the natural daylighting performance. Eventhough it is unknown whether parametric or environmental analysis tools were implemented in the HMA expansion project, two previous studies showed that the existing pointing skylight system used in the building met the required daylight standard. In addition, the use of the parametric method could verify and even more offer an optimal solution for the skylight system. Nevertheless, further detailed study is needed to inspect energy efficiency and its relationship with operational cost.

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