Exploration into formal aesthetics

in design: (material) texture


Dr Hengfeng Zuo, PhD, MSc, MA

Research Fellow in Product Design

Faculty of Technology, Southampton Solent University, UK

Email: heng-feng.zuo@solent.ac.uk


Mark Jones, BA, MCSD

Senior Lecturer in Product Design

Faculty of Technology, Southampton Solent University, UK

Email: mark.jones@solent.ac.uk





The connotation of aesthetics can include a number of aspects such as technological aesthetics, functional aesthetics, formal aesthetics, psychological and cultural aesthetics and so on. Formal aesthetics concerning shape, colour, materials, texture, space etc (and of course their combination) is the fundamental target that designers should exclusively achieve, which radically/directly determines the ‘styling’ of any 3D product and environment. Our research focuses on the systematic investigation into the material texture. Compared to colour, texture is a less identified property. Although an increasingly wide range of materials with abundant textures and surface effects are currently available in market, little has been understood about how human (both designers and users) respond and perceive them, either physiologically via their senses such as vision, touch etc or psychologically and culturally via their mind. This part of knowledge will enable design practitioners to take into consideration the rational thinking of texture creation and application as assistance to their innovative practice. Based on experimental research with speculative research, and combining with examples, this paper addresses a series of issues about texture, including the concepts of and clarification between texture and perceived texture (texture perception); the dimensions of verbal description of texture; psychophysical relationship between subjective feelings of texture and physical parameters of materials; also addressed is the resources and inspirations from where texture can be generated.


Key words: texture, aesthetics, materials, sensation and perception, design



1.    Introduction


Aesthetics, usually defined as the branch of philosophy that deals with the nature and expression of beauty [1], has been recognised since antiquity and has continually evolved over time. The word beauty is commonly applied to things that are pleasing to the senses, imagination and/or understanding. It is often what an artist or a designer makes great efforts to achieve in their works, either for personal or mass interest and pleasure. Aesthetics can have different meanings from different perspectives of approach and study. For example, a designed and manufactured artefact can be judged as beautiful or pleasing because of its unique functions (functional aesthetics), the application of advanced technology (technological aesthetics), its fascinating form characteristics such as attractive shape, colour, texture etc (formal aesthetics), or its representation of life experience and social identity or a symbol of cultural reflection (psychological and cultural aesthetics). These aspects are twisted together in their contribution to the whole perception of product aesthetics. Figure 1 shows a kettle that uses smart material to give a particular function of indicating the water temperature. This is realised by the colour changes of the thermo-sensitive material at different temperatures. At the boiling point, the material turns into a red colour. The product gives you a sort of fun in addition to fulfil its basic function of boiling water. It is a trend for consumer products to have their unique personalities and evoke emotional feelings such as pleasure within the context of today’s consumption culture. We can see from this example that how interaction between technology (smart technology), function (temperature indication), form (materials, colour), and culture (consumption culture, emotions and pleasure) contributes to product aesthetics.

However, it is widely agreed that, in the first instance, aesthetic experience comes from the senses, or sensations [2], [3]. When we say that a colour is beautiful, a smell is nice, or a texture is fascinating, it is because the colour, or the smell, or the texture gives you the sensory pleasure to your sensory organs such as eyes, nose, skins/muscles, etc. In addition, they may evoke some positive associations with anything in your memory, life experience, social events etc. This is why formal aesthetics, which mainly concerns shape, colour, materials, texture, space and proportion etc (and of course their combination), is a fundamental goal that designers should try to achieve. These formal elements radically determine the ‘styling’ of any 3D products and significantly influences users’ perception of the product’s beauty and value.


Research evidence shows that the sensory and perceptual aspects of colour and sound have been widely explored. This is not the case with texture, particularly tactual texture, or smell and taste. Compared with the properties of colour, sound etc, texture seems to be a property that is more ambiguous and difficult to identify. We can use three dimensions of hue, lightness and saturation or the RGB parameters to describe and accurately specify and identify a particular colour. A series of standard colour systems such as Munsell, Pantone, NCS etc are available for colour specification in the market place. However, we tend to know much less about how to specify a texture, and even less as to how to identify a unique texture. Although due to development in computer science, it is possible to design, manipulate, and retrieve a texture, it is dominated in the case of two dimensional images or virtual images. Systematic understanding about texture in a wider range of areas, beyond merely visual images, and particularly including the textures of physical materials, has not been extensively explored. This paper has a probe into the material texture perception from the practical perspective of design. In this context, we will skip the black box that deals with the mechanism about how texture information is processed in the brain, but focus on a more peripheral aspect. This includes a texture’s definition and classification; how people subjectively describe a texture; how subjective responses to texture can be related with objective texture parameters; and what are the sources for a texture to be generated in the design practice.  


2.    Concept of texture


The word ‘texture’ was originally a textile term, a quality of fabrics appraised and appreciated through the sense of touch [4] (Figure 2).  The concept was then expanded to a wider range from a philosophical and cognitive angle of view. Cognitive scientists have recognised texture as a visual cue [5] that plays a significant role in a variety of cognitive tasks. A common use is in describing and differentiating between different kinds of objects, either two-dimensional for example an image, or three-dimensional for example wallpaper, furniture, carpets, sand, and grass etc. A working definition of texture in this context is the surface markings on an object or the 2-D appearance of a surface [5].  However, this definition is one-sided because texture is not merely a visual cue, but could be served as the cue of other senses. For example, texture should go beyond merely surface markings, and should concern other characteristics such as the moisture retention level, thermal conduction, temperature, softness or hardness etc. Texture, in a wider range of understanding, can also be used to depict the structure of other things such as a poem, a piece of music [4].


Due to the standpoint of approaching the research from 3D design perspective, we would like to narrow down the meaning of texture within the context of physical materials. Within this context, texture can be understood from two aspects or two scales. On one hand, it is appreciated for a material’s visual appearance and tactual feel at the macro scale (Figure 3). On the other hand, texture was transplanted to a more specific term in the study of materials science and engineering. In this field of study, texture means a particular orientation distribution in microstructure. When a piece of metal is deformed by some directional process such as wire-drawing, extrusion, or rolling, the constituent crystal grains acquire a preferred orientation. This orientation is called texture [6] (Figure 4). The orientation can result in changes of material properties. Nevertheless, because of its micro-scale magnitude (the crystallitic grain size is usually from 1mm to 100mm or even smaller from 1nm to 100nm (nano-materials), texture under this context is difficult for a human to perceive directly by sensation. This texture can only be tested and analysed by means of specialist equipment such as an X-ray diffraction device or microscopy etc. However, these two aspects of material texture can be, although not always, related. For example, a shiny, transparent texture of diamond is related with its specific crystal structure where carbon atoms are arranged in a face-centred cubic lattice and with a regular tetrahedral structure. The various textures shown on the section surface of different types of wood are determined by their growing mechanism. At the rest part of the paper, we will focus on the exploration of material texture from the sensory and macro aspect.


It is necessary to discriminate between two concepts. One is texture; the other is perceived texture or texture perception. The former is objective, whilst the latter is subjective. We propose to define ‘texture’ as ‘the geometrical configuration and physical-chemical attributes of surface or bulk of materials/objects’. Correspondingly, we propose a definition of perceived texture as ‘a synthesis of physiological and psychological response and impression to the geometrical configuration and physical-chemical attributes of the surface or the bulk of materials/objects’. In this definition, the ‘synthesis’ means it is not simply ‘A (geometrical configuration) plus B (physical-chemical attributes)’ but ‘A fusing with B’, therefore the subjective responses to A and B would interact. Although under certain conditions (e.g. by vision), the response to geometrical characteristics may be dominant over physical-chemical attributes of texture, or the inverse, under other conditions (e.g., by blindfold touch).  What’s more, the subjective response will possibly go beyond these two aspects as can be found in our experimental research. The understanding of the correlation between the objective texture attributes (usually represented by physical parameters) and the subjective texture perception will provide the framework for creating suitable, aesthetic material textures.



3.    Classification of texture


Texture can be categorised in different ways from different viewpoints. Following are some of the examples of texture categories:


§         Natural texture and artificial texture (according to the formation of texture);

§         Regular texture and random texture (according to the pattern of texture);

§         Visual texture and tactual texture (according to the perceptual modality);

§         Virtual texture and real texture (according to the representation of texture).


However, these classifications of texture can also be intersected. For example, a wood texture can be attributed as a natural texture. At the same time, it can be a random texture due to its freely scattered line-patterns. With a particular surface treatment, for instance, by a layer of other material coating (e.g. varnish, lacquer) on wood surface, it can also have the attributes of artificial texture. If presented as an image, it is a visual texture. If it is simulated by computer software, then it is virtual texture. When it is presented as the surface of a piece of furniture, it is visual plus tactual texture, and also a real texture.


4.    Subjective description of texture


In the design field, knowing how people describe the sensory properties contributing to formal aesthetics, including colour, texture, sound smell, etc, will ensure a consistent communication language between designers and consumers and enable designers to establish criteria for a product if it is to achieve good sensory adaptation and aesthetic expectation. Researchers have tried to find the dimensions for texture perception in the cases of different material categories such as building materials [7], wood [8], paper [9] and leather [10], [11] etc. However, all the character dimensions (words or word pairs) of texture description are different between researchers and show a lack of a systematic classification.


From our experimental research, a {Dimension-lexicon} system [12] has been proposed to summarise the material texture description. It is generally accepted that the subjective description of material texture can be summarised into four dimensions: geometrical dimension, physical-chemical dimension, emotional dimension and associative dimension. Each dimension has a number of descriptive words that are most frequently used by subjects. These words are put into pairs that have bipolar meanings such as hard – soft, shining – non-shining etc, and are named as texture lexicons. However, the texture lexicons will slightly change in quantity, and frequency of being used when the controlled condition is changed. These conditions include sensory modality, material categories, subject background etc.


Geometrical dimension This dimension describes the subjective response to the geometrical configuration of a material surface. The texture lexicons within geometrical dimension include the description of a material surface in two aspects: One is the global, macro impression of the surface configuration, i.e. the surface pattern, such description as plain – bumpy, regular – irregular, repetitive – non-repetitive, line-scattered – dot-scattered, simple – complex etc. The other is the local, micro feeling of the surface configuration, i.e. the surface roughness, described as smooth – rough, fine – coarse etc. Therefore, a plain surface can be rough, whilst a bumpy surface can be smooth. Figure 5 shows an Aluminium texture that is globally bumpy but locally smooth. However, the discrimination between the surface pattern (macro) and surface roughness (micro) is sometimes ambiguous.


Physico-chemical dimension This dimension describes the subjective response to the physical and/or chemical attributes of a material surface. It includes the dynamic characters that need energy exchange (such as mechanical, thermal, optical, etc) with environment and is time-related. High-frequency lexicons used in this dimension include such as: warm – cold, hard – soft, moist – dry, shiny – non-shiny, sticky – non-sticky, etc.


Emotional dimension This dimension describes the affective, hedonic, valuable feelings that are evoked by touching the material surface. High-frequency lexicons in this dimension include such as: comfortable – uncomfortable, lively/cheerful – dull, elegant – ugly, modern – traditional, etc. Subjects seem to be more sensitive to the emotional feelings under the visual touch conditions. However, when blindfolded, subjects are still equally sensitive to the feeling of comfort comfortable – uncomfortable when touching the material surface [12].


Associative dimension This dimension describes the subjective association from the material, i.e. to what existing things in the perceiver’s life experience can the texture be compared. This description is beyond the description of geometrical and physico-chemical characteristics, and is much more individually dependent. Therefore the lexicons in this dimension are random, and have low frequency, but they are rich in description. Figure 6 shows some examples of such associative descriptions. Understanding of this association can be helpful in texture selection in order to integrate positive user experience to the context where the texture is applied.


e. buddhist


d. silky


c. oily


b. honeycomb-like


a. feather-like


Figure 6 associative description of material texture





5.    Psychophysical relationship in texture perception


There are often certain physical parameters of materials that underlie or correspond to subjective descriptions of texture. It is the parameters that determine the objective side of texture. Understanding the relationships between the objective parameters and subjective responses will help to further identify the technical aspects of texture selection, to pinpoint particular technical processes for materials and surfaces with suitable parameters, which correspond to the maximising mixture of positive user feelings. This will have great significance in the new product development process.

This type of knowledge can actually be traced back into Psychophysics, the oldest stream of psychology that particularly explores the relationship between physical world and mental world. An example can be found in the study of sound, the physical intensity of sound is different with psychological intensity of sound. The latter is then called loudness. Loudness is a psychological experience that correlates with, but not identical to, the physical measurement of sound intensity. For example, an 80db sound does not sound twice as loud as a 40db sound, and the increase from 40db to 50db will not be judged as the same loudness increase as that from 70 to 80db [13]. Similar relationship needs to be explored in the case of texture.

We have conducted experimental research to find a relationship between subjective feeling of materials with physical parameters such as roughness and hardness [14]. It needs to be pointed out that the traditional psychophysical research focuses on two variables that address the same stimulus (say, roughness, or warmth, or softness etc), of which one is physical, and the other is psychological.  In addition to this ‘one to one’ relationship, a ‘one to more’ or ‘more to one’ relationship is also worth exploring as long as this kind of relationship does exist. For example, people’s psychological feeling of a surface’s moisture could be related to a number of physical factors, such as different materials with different surface energy[1], or the same type of materials with different surface roughness, or the same type of materials but with different softness [11]. On the other hand, one physical parameter, e.g. the physical roughness, can correspond to a number of psychological feelings, e.g. subjective roughness, stickiness, warmth. The relationship between physical roughness and psychological roughness tends to conform to a power law [7] [14]. We are currently also investigating the quantitative relationship between psychological responses to material texture and the material surface gloss.



6.    Resources & inspiration of texture generation


In general, when a designer makes a decision to use a particular texture, either a material texture in a 3D context or an image texture in a 2D context[2], the decision will usually be based on three aspects: knowledge, inspiration, and experience. Knowledge is rational, and inspiration is intuitive, whilst experience offers reference of synthetic information from practice.  From the perspective of generating a visual effect of texture, there is little difference between material texture (3D) and image texture (2D). However, from the perspective of realising the visual effect on a physical surface, the decision making of texture selection will be more complex as there will exist certain constraints from the technical side (e.g. manufacturing processes). At the same time, not just visual attributes but also tactual feelings or other sensory attributes (sound, smell etc) need to be considered as well. In such cases, knowledge including the issues discussed in previous sections such as subjective description of and responses to a texture, psychophysical relationship of texture perception, material properties and manufacturing processes will be necessary. The following listed are mainly the aspects that will stimulate the generation of a texture (either a material texture or an image texture).


6.1   Texture learnt from nature


Natural texture is the texture formed by the natural forces such as a thunderstorm, wind, rain, river etc (e.g. the stone texture), or resulting from the internal atomic structure of substance (e.g. the diamond shiny texture) or by the original/primitive growing mechanism of life (e.g. the texture of leaf, wood). Figure 7 shows examples of some natural textures. No matter what kind of natural texture, such as the random linear texture of wood, or the smooth and marvelous texture of pebbles, or the fine, soft and wavelike desert texture, the leaf, the ice, the animal skin, … all the natural textures not only give us an enjoyment of beauty and harmony, but also give us abundant inspiration, as sources of creativity, particularly in the aspect of pattern.








6.2   Texture created from the mind, fantasy


In this case, texture is regarded as the component of any image in people’s mind, which becomes a graphic picture when presented via a certain media.  Any images in human brain will not come from a vacuum, but from their life experience and memory. But only the experience and memory are not enough so that not everybody can produce an astonishingly attractive image and become so-called ‘artist’. Free Imagination and fantasy based on that experience is decisive factor. Here, people’s accumulated life experience and sensitivity to art promotes each other. Examples of textures coming from this kind of fantasy are shown in Figure 8. A deliberate strengthened training in graphic presentation will be a worthy route to stimulate the creative thinking of a 3D designer, particular industrial product designer in their practice.








6.3   Texture generated from virtual reality


In authors’ opinion, the functional meaning of things existing in virtual reality at least has two aspects. Firstly, it is physical-reality targeted. In other words, it is the preparatory trial or forerunner for any events in physical world, with the purpose of as a testifier or communication for save time and expenses. Such examples include all kinds of CAD design. Secondly, it is virtual-reality itself targeted. As the feature of digital times, virtual reality has become a type of culture. People can enjoy a life style by making friends, playing games within the virtual reality. In either case, it is required that texture of presented images has satisfactory simulation with those in the real world. A series of computer software can make this available. In addition to vividly simulating the textures from the physical world, the digital tool can also produce any non-realistic texture, facilitating people’s fantasy mentioned in 6.2. Some examples of virtual textures are shown in Figure 9.








6.4   Texture resulted from advancement of science and technology


The relationship between a surface effect/texture and the innovation in science and technology is two directional. Most cases might be searching for a technical method to convert a texture from a drawing board to a 3D material surface. In these cases, the innovative technology can give the opportunities of realising different surface finishes and textures that were unavailable before. For example, through in-mould coating technology (Figure 10 c. and d.), various surface effects either for decoration or for specific functions (such as impact resistance, crack resistance) can be realised [15]. And it can be tailor-made in line with customer requirements. Figure 10 a. shows a texture resulted from a photo-etching process by which a photographic image is transferred onto a metal surface via either silkscreen or photocopy transfer. On the other hand, in some cases, the advancement in science and technology offer unexpected surface effects, which further stimulates creative practice. For example, nano-technology, by manipulating the micro-size of pigment grains, dramatically improve the look of plastics, inks, coatings, ceramics, cosmetic and personal care products, automobile and industrial finishes.








6.5   Texture existing in the micro-world


Usually only a few people have a frequent contact with the micro-world. For instance, a material scientist often looks at the microstructure of a piece of metal; a life scientist examines the DNA composition of an organism sample. Most of other people will neglect this marvellous world. However, information and images within this micro-world not only can give us scientific proof supporting new knowledge about the macro world, but also is a source of inspiration for beauty and art. Sometimes, we can find the images from micro-world and macro-world have some astonishing similarities. Figure 11 shows some examples of the micro-textures observed from microscopy. In addition to appreciate the subtle beauty of the textures, we might be able to get some lessons and enlightenments.








6.6   Texture derived from social events


Looking at the geometrical or spatial aspect of texture, in a wider sense, we can regard texture as the structural arrangement of the components consisting anything in the world, including the images of social events. These events emerge here and there from day to day. And the images of these events can also be a source of inspiration in texture generation. Figure 12 shows the textures of the night sky with various effects of fireworks. It is understandable that art practice and creation has a significant relationship with social activities.








7.    Conclusions


Formal aesthetics is the fundamental aspect contributing to the whole perceived aesthetics of an artefact. Sensory adaptation and pleasure (from colour, texture, sound etc) is the core content of form aesthetics. Material texture plays a decisive role in the perception of the whole product’s beauty and value. To understand and identify a texture, three streams of information are necessary: one, the objective parameters that determine the geometrical, physical or chemical attributes of the texture; two, the subjective description of texture and human responses to texture through different sensory routes; three, the psychophysical relationship between the above two aspects. Texture can be generated or learnt from nature, mind & fantasy, innovation in science & technology, virtual reality, micro-world and social events. 





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[1] Surface energy (sometimes also called surface free energy) is defined as the energy required for creating unit area of a new surface. It influences the surface adsorption with liquid articles, which will be related with the feeling of moist.

[2] 2D image also reflect 3D information, here the meaning of 2D refers to as the media (screen, paper) through which the texture is presented, compared with the 3D physical materials/objects.