ARCOmadrid 2025: EN

 

 

 

 

Regina Silveira’s artistic research questions the orthodox, preestablished forms of representation, leading her to work with new possibilities of signification. Her works explore the architectural and contextual space, generally evoking a sense of uncanniness through the displacement of the commonplace, that is, our common references. Regina Silveira is known for her research into the principles of perspective, tridimensionality, and the study of shadows, which she employs in large site-specific installations, vinyl cutouts, luminous projections, works in printmaking, embroidery, porcelain and digital videos.

With a BA in arts from the Instituto de Artes do Rio Grande do Sul (1959), an MA (1980) and PhD in art (1984) from the School of Communication and Arts of the University of São Paulo (ECA USP), her career as a professor includes stints of teaching at the University of Puerto Rico, Mayagüez; at FAAP, São Paulo; and at ECA USP. She was an invited artist at the 1981, 1983, 1998 and 2021 editions of the Bienal de São Paulo, the 2013 and 2015 editions of the Bienal Internacional de Curitiba, and the 2001 and 2011 editions of the Bienal do Mercosul. She participated in the Bienal de La Habana, Cuba, in 1986, 1998 and 2015; Mediations Biennale, Poznan, Poland, in 2012; the 6th Taipei Biennial, Taiwan, in 2006; and the 2nd Setouchi Triennale, Japan, in 2016. Most recently, in 2025, the artist presented her largest commissioned work ever held, Paradise, at IAH Terminal D - George Bush Intercontinental Airport, in Houston, USA. The artist’s work also has been presented in a major retrospective at Museu de Arte Contemporânea – MAC-USP, 2021-22, as well as at La Virreina Centre de La Imatge, Barcelona, Espanha, 2024; Paço das Artes, São Paulo, 2020; the Museu Brasileiro da Escultura (MuBE), São Paulo, 2018; the Museu Oscar Niemeyer, Curitiba, 2015; the Museo Amparo, Puebla, Mexico, 2014; the Fundação Iberê Camargo, Porto Alegre, 2011; Atlas Sztuki Gallery, Lodz, Poland, 2010; Masp, 2010; and the Museo Nacional Centro de Arte Reina Sofía, Madrid, Spain, 2005. Regina Silveira was awarded the Prêmio Masp (2013), the Prêmio APCA for her career (2011), and the Prêmio Fundação Bunge (2009). She has received grants from the Fulbright (1994), Pollock-Krasner (1993) and Guggenheim (1990) foundations, and her work figures in countless public and private collections, such as those of the Cisneros-Fontanals Art Foundation (USA), Inhotim, Coleção Itaú, El Museo del Barrio (USA), MAC-USP, Masp, MAM-RJ/SP, the Pinacoteca de São Paulo, MoMA (USA), and the Phoenix Museum (USA).

Waldemar Cordeiro was a key figure in the development of concrete art, a vanguard movement essential for the transition of modern art to contemporary art, which came to define 20th-century Brazilian art. Besides being a pioneer in computer art as early as the 1960s, Waldemar Cordeiro developed and implemented important landscaping designs in Brazil. In his interdisciplinary research he defended painting in its essence, with self-supporting basic colors and lines, without the backing of figurative representation. He was notable for his objective and rational art, very much associated with his theoretical studies, as well as for his investigation of industrial materials and elements. Cordeiro worked for an art accessible to all, seeking a collective sense that was also aligned with technology, to design and to landscaping. His research in art was always coupled with a social and political concern.

Waldemar Cordeiro studied at the Academy of Fine Arts of Rome (1938) and at the Tasso Lyceum of Rome (1945). In 1949, he took up residence in Brazil. He participated in the inaugural show of the Museu de Arte Moderna of São Paulo (MAM-SP), Do figurativismo ao abstracionismo (1949), and in the 1st Bienal de São Paulo (1951). He was also one of the organizers of the show Ruptura, also at MAM-SP (1952), and of Arteônica, at Fundação Armando Alvares Penteado, FAAP-SP (1971). Solo shows of his work have been held at noteworthy venues, including the permanent show online Waldemar Cordeiro: Bits of the Planet, MAM-RJ/SP, CCSP, Buffalo University (USA), MAC-SP, Itaú Cultural, São Paulo, and the Paço Imperial, Rio de Janeiro. Group shows featuring his work have been held at important venues which include the Walker Art Center (USA), the Pinacoteca de São Paulo, the Museum of Fine Arts Houston (USA), the Museum of Modern Art (MoMA), New York (USA), CCBB-SP/RJ, Goethe-Institut, New York (USA), the Museo Nacional Centro de Arte Reina Sofía, Madrid (Spain), Instituto Tomie Ohtake, São Paulo, the Venice Biennale (2024), the Bienal de São Paulo (2012, 1975, 1973, 1969, 1967, 1965, 1963, 1961, 1959, 1957, 1955, 1953 and 1951), and the Biennial of Nuremberg (Germany). Waldemar Cordeiro’s works figure in many prominent collections, including those of the Cisneros Fontanals Art Foundation (USA), the Museu de Arte Contemporânea of the University of São Paulo, the Patricia Phelps de Cisneros Collection (USA), the Pinacoteca de São Paulo, the Museum of Modern Art (MoMA) of New York (USA), the Museum of Fine Arts, Houston (USA), and ZKM Museum (Germany).

Geraldo de Barros is a key name of 20th-century Brazilian art. Combining his first studies on painting with a later interest in photography, he pushed the envelope of the traditional photographic processes, questioning the classic rules of composition. Geraldo de Barros took a formal concern – as clearly seen in Brazilian concretism, in which participated intensely – and managed to merge this with his social concerns, leading him to approach the industrial processes in his work, dealing coherently with geometric constructions, reproducibility, the socialization of art, the theory of form and industrial design.

At the age of 26, Geraldo de Barros participated in the creation of the photography course and darkroom at the Museu de Arte de São Paulo (Masp), where he presented the exhibition Fotoformas, in 1950. The artist was also one of the most active members of the Foto Cine Clube Bandeirante, which marked the experimentation of photography in Brazil. In 1951, he participated in the Hochschule für Gestaltung (HfG – School of Design) in Ulm, Germany. He was also one of the founders of Grupo Ruptura (1952) and of Grupo Rex (1966), and participated in the 1st, 2nd, 9th, 15th and 21st editions of the Bienal de São Paulo, and in the 1986 Venice Biennale (Italy). Geraldo de Barros’s works have participated posthumously in various national and international exhibitions. In 2014, Instituto Moreira Salles, in Rio de Janeiro, organized a retrospective of the artist, and in the following year the same exhibition was held at Sesc Belenzinho, in São Paulo. In 2017, the Fundação Arpad Szenes-Vieira da Silva in Lisbon (Portugal) and the Document Gallery, in Chicago (USA), held solo shows featuring works by the artist, followed by others at Side Gallery, in Barcelona (Spain), in 2018, and Kunst- und Kulturstiftung Opelvillen, in Rüsselsheim (Germany), in 2019. In 2021, Itau Cultural featured a solo exhibition, while in 2022, the Museé d'Art Moderne et Contemporain – MAMCO, in Switzerland, held the largest retrospective of the artist in Europe. His work figures in important collections such as those of the Fundação de Arte Cisneros Fontanals, the Art Fund of the State of Geneva, the Fundação Bienal de São Paulo, Instituto Inhotim, the Ludwig Museum, the Max Bill Foundation, the Max Art Museum, the Museu de Arte Contemporânea of São Paulo, the Museu de Arte Moderna of São Paulo, the Museu de Belas Artes, the Museu de Arte de São Paulo, MoMA, Tate Modern, Photographer’s Gallery, the Pinacoteca de São Paulo, the Museo de Arte Latinoamericano de Buenos Aires, and others.

Bosco Sodi’s research is outstanding for its simplicity of materials from a natural origin, such as pigments, sawdust, fibers, wood, soil, etc. The combination of these elements with the gesturality of his production makes each work unique, while creating a special connection between the artist and his process of creation, which transcends the conceptual. Currently, he has been making increasing use of techniques from olden times, which not only establish a direct relationship with the ethnobotanical discourse, but also recover his native Latin American ancestrality. Bosco Sodi also associates these techniques to traditional and contemporary processes, dialoguing with the movements of land art and informalism.

He has presented solo shows at prominent institutions that include He Art Museum (2024, Foshan, China), Casa das Rosas (2024, São Paulo, Brazil), Harvard Art Museum (2023, Cambridge, USA), Fundación Casa de Mexico (2023, Madrid, Spain), the Fondazione dell’Alberto d’Oro, Venice, Italy (2022, as part of the official program of Venice Biennale); University of South Florida Contemporary Art Museum, Tampa, USA (2021); CAC Málaga, Spain (2020); the Royal Society of Sculptors, London, England (2019); the Museo di Scultura Antica Giovanni Barracco, Rome, Italy (2019); the Mexican Cultural Institute, Washington, DC, USA (2019); the Museo Nacional de Arte, Mexico (2017); and the Bronx Museum, New York, USA (2010). He has participated in group shows at venues that include the Ryosokuin Zen Temple (2024, Kyoto, Japan), Desert X (2024, AlUla, Saudi Arabia), Converge 45 Biennial (2023, Oregon, USA), Harbour Arts Sculpture Park, Hong Kong (2018); the Museum of Modern Art, Gunma, Japan (2017) and the Museo Espacio, Mexico (2016). Bosco Sodi’s work is also part of important collections such as Colección JUMEX (Mexico), the Harvard Art Museums (USA), the Museum of Contemporary Art San Diego (USA), the New Orleans Museum of Art (USA), the Scottish National Gallery of Art (Scotland), and Walker Art Center (USA).

The appeal of Iván Navarro’s works springs from a combination of elements that question our perception. On the one hand, from a formalist point of view, his works are carefully constructed, having light as their main support. Light that arouses feelings, at the same time that it sparks enchantment in the spectator. Iván Navarro’s production is also imbued with political connotations, communicated to the public through countless strategies, as seen in the titles of his works, in his careful use of color, in the use of anagrams, or in the appropriation and deconstruction of symbols that represent ideologies and institutionalized power. 

 

Iván Navarro graduated in visual arts, in Santiago, Chile, in 1995. He has held solo shows at prominent institutions such as La Capilla Azul, Chiloé, Chile (2024), Micromuseo di arte Contemporanea della Tuscia, Italy (2023), Art-OMI Sculpture Park, Ghent, USA (2022), Farol Santander, São Paulo (2020); MAC – Niterói, RJ (2019); MACBA, Buenos Aires, Argentina (2019); the Museu Nacional de Belas Artes, Santiago, Chile (2015); and the Espace Culturel Louis Vuitton, Paris, France (2010). Titles and venues of group shows he has participated in most notably include the Centro de Arte Caja de Burgos, Burgos, Spain (2024), Illuminate SF Festival of Light, São Francisco, USA (2020); the XIV Bienal de Nuevos Medios, Museo Nacional de Bellas Artes, Santiago, Chile (2019); the 13th Biennale of Cairo, Egypt (2019); MACBA, Buenos Aires, Argentina (2018); Guggenheim NY, USA (2018); the Museo del Barrio, NY, USA (2017); MuBE-SP (2016); the Centro Nacional de Arte Contemporáneo, Santiago, Chile (2016); the 10th Bienal do Mercosul, Porto Alegre (2015); the Cairo International Biennale, Egypt (2010); the 53rd Biennale di Venezia, Italy (2009); and the 2nd Moscow Biennale, Russia (2007). His works figure in the collections of important institutions such as the Centro Galego de Arte Contemporánea (Spain), the Fonds National d’Art Contemporain (France), the Hirshhorn Museum and Sculpture Garden (USA), Inhotim, the Museum of Fine Arts (Boston, USA), the Saatchi Collection (England) and the Solomon R. Guggenheim Museum (USA).

An indigenous artist from the Mayan Tz'utujil people, Antonio Pichillá works with a variety of media, but finds textile weaving as his main focus of interest. For him, the processes and materials that involve textile traditions represent a way of rescuing his ancestry, especially through the memory of the women of his own family. His research is also based on the collectivity, culture and symbols of his people, native from the Lake Atitlan region (Guatemala).

 

Antonio Pichillá graduated from Escuela Nacional de Artes Plásticas Rafael Rodríguez Padilla, in Guatemala. He is a member of TEI-CA group (Study and Research Workshops in Science and Art). Among his most important solo shows is the one that was featured at the International Centre of Graphic Arts – MGLC (2024, Slovenia), Museum of Contemporary Art Santa Barbara (2023, USA), La Nueva Fábrica, Santa Ana (2022, Guatemala). As for the group shows, the most important are: Barbican Centre (2024, UK), The Institute for Studies on Latin American Art ISLAA (2024, USA), 22nd Bienal Sesc VideoBrazil (2023-24, Brazil), Denver Art Museum (2022, USA); Kathmandu Triennial (2022, Nepal), 11th Berlin Biennial (2020, Germany), Arte Paiz Biennial (2002, 2010 and 2014, Guatemala), etc. His work features in relevant collections, such as Museo Nacional Centro de Arte Reina Sofía (Spain), Denver Art Museum (USA) and Tate Modern (UK). Some of his prizes are: Intercontinental Indigenous Biennial - Honorable Mention (2012, Mexico) and Juannio Latin American Art Contest / Auction (2017, Guatemala).

Caio Reisewitz’s research takes photography as its main medium. Through technical and thematic refinement, his work evinces an interest in human action and its social and political effects, whether in the natural space or the architectural space. While his photographic technique highlights the dramaticity among shapes, colors and textures, his artistic poetics constructs a nearly dreamlike aesthetic repertoire. These aspects establish a dichotomous dialogue between the real (that which is characteristic of the photographic record) and the chimerical (our own repertoires).

 

With a degree in visual arts from Mainz University (Germany), Caio Reisewitz has an advanced degree in visual poetics and an MA from the University of São Paulo. The biennials he has participated in include: 23rd Sydney Biennale (2022), Biennale des Arts 2022 de Nice, France,  the 26th Bienal de São Paulo (2004), the 51st Biennale di Venezia (2005), in Italy, and the Nanjing Biennale (2010), in China. His work has also been shown at the Fundació Mies van der Rohe (2024, Barcelona, Spain), 22nd DongGang International Photo Festival, Dong Gang Museum of Photograph (2024, Coreia do Sul); Museo de Arte Contemporáneo de Castilla y León (MUSAC) (2024, 2023 and 2010, Spain); Instituto Moreira Salles, Rio de Janeiro and São Paulo (2010); the Ella Fontanals-Cisneros Collection Miami (2005, 2010, USA); the International Center of Photography (ICP), New York (2014, USA); the Maison Européenne de la Photographie, Paris (2015, France); the Pinacoteca de São Paulo (2017), as well as at Photo Shanghai (2019, China). In 2020, he released the book Altamira, based on a collection of the same name acquired by the Pinacoteca de São Paulo. His work figures in important collections such as those of the Cisneros Fontanals Art Foundation (USA); the Fundación ARCO Madrid (Spain); the Collezione Fondazione Giovanni Guastalla (Italy); the Fond National d’Art Contemporain (France); MUSAC (Spain); the Museu de Arte Moderna (MAM) of São Paulo, of Rio de Janeiro and of Salvador (Brazil); the Musée Malraux (France); and the Pinacoteca de São Paulo.

Gabriela Machado’s research is focused mainly on painting. The imagery of day-to-day experience is a great source of inspiration, providing the artist with parameters for landscapes and still lifes, in which she emulates small slices of everyday life on the canvas. Her processes spring from quick, organic and spontaneous gesturality, lending pure visuality to the lively colors and forms. As an outgrowth of this aesthetics, she also creates sculptures, in which she investigate shapes through the potentials of other materials, such as clay, plaster and bronze.

 

Gabriela Machado received her BA in architecture from Universidade Santa Úrsula (RJ), in 1984. She then furthered her studies in art at the Escola de Artes Visuais do Parque Lage (RJ), between 1985 in 1993, as well as in open courses. She has held solo shows at notable venues including Fundação Eugênio de Almeida (2019, Évora, Portugal), the Museu de Arte de Santa Catarina (2018, Santa Catarina), Auroras (2017, São Paulo), MAM (2016, Rio de Janeiro), the Espaço Caixa Cultural (2009, São Paulo and Rio de Janeiro), and the CCBB (2002, Rio de Janeiro). She has participated in group shows held by prestigious museums and organizations that include Paço Imperial (2014, Rio de Janeiro), Oi Futuro (2014, Rio de Janeiro), Instituto Figueiredo Ferraz (2012, Ribeirão Preto) (2012, São Paulo), Centro Cultural São Paulo (2011, São Paulo), the Museu de Arte da Pampulha (2010, Belo Horizonte), Centro Universitário Maria Antônia (2002, São Paulo), and MAM (1999, Salvador). Her work figures in the collections of important institutions, including those of the Museu de Arte da Pampulha (Belo Horizonte), the Instituto Brasileiro de Arte Contemporânea (IBAC, Rio de Janeiro), and the Museu de Arte de Santa Catarina (Santa Catarina).

Technical rigor is one of the main characteristics of the work of Rafael Carneiro, who over the years has been transforming within painting. The transcription of images to the canvas has become, in and of itself, the main thematics of his work, which seeks to avoid the formal commitments and labels proper to painting in order to approach the complex world of the images of culture and the collective imaginary. The meaning of the figures used by the artist is diluted by the technique he uses, which decontextualizes, reconfigures and resignifies, through the breaking of their integrality, subtracting and adding new elements, in order to compose more complex narratives. To this end, Rafael Carneiro uses a vast private collection of images, which he freely articulates with various forms of composition, through an organic creative process that often includes music.

 

Rafael Carneiro holds a BA in visual arts from ECA USP. His works have been shown at many institutions including the Centro Cultural Banco do Brasil, CCBB-DF and RJ (2019); the 33rd Bienal de São Paulo (2018); the Pinacoteca de São Paulo (2017); the Caixa Cultural Rio de Janeiro (2017); Instituto Tomie Ohtake, São Paulo (2016 and 2013); the Paço das Artes, São Paulo (2014); the Festival Sesc_Videobrasil, São Paulo (2013); Itaú Cultural, São Paulo (2011); the Centro Cultural São Paulo (2009 and 2006); and the Centro Universitário Maria Antonia, São Paulo (2005).

Raphaël Zarka's artistic research starts from theoretical experimentalism, which crosses various media, including painting, sculpture, photography and video. His main interest lies in the sculptural potential of structures, their volumes and geometries, influenced by architecture and urbanity. The artist frequently collaborates with local communities to create his projects, which explore the history and materiality of the objects and spaces involved. Skateboarding, in particular, represents an important element in his investigation, not only for the culture that surrounds that practice, but also for the dynamics of the surfaces used, such as ramps. Also, it is worth mentioning that the point of convergence of his work is a change in the meaning of the forms according to the space and time in which they are inserted.

 

Raphaël Zarka graduated in Arts from the Winchester School of Art, in England, and from the École Nationale Supérieure des Beaux-Arts, in Paris. Among the solo exhibitions, there are the ones at Center Georges Pompidou (2024, Paris, France), Center régional d’art contemporain, (2020, Le Havre, France), Koffler Center of the Arts (2019, Toronto, Canada), National Museum of Contemporary Art (2019, Romênia), Musée d’Art Modern (2016, Toulouse, France), Le Corbusier – Villa Savoye (2013, French), etc. His main participations in group exhibitions are: Biennale d'art contemporain d'Enghien (2022, Belgium), Center Regional d’Art Contemporain (2021, Montbéliard, France), Museé d’Art Contemporain (2019, Bordeaux, France), Museo Nazionale delle arti del XXI Secolo (2018, Rome, Italy), Center Georges Pompidou (2016, Paris, France), Museu de Arte do Rio – MAR (2014, Brazil), Palais de Tokyo (2012, Paris, France), Museum of Contemporary Art (2010, Detroit, USA), etc. His works feature among various public and private collections, such as Center George Pompidou (France), Fonds National d'Art Contemporain (France), Museé d'Art Moderne de Paris (France), among others.

Analivia Cordeiro develops her artistic research in a hybrid and multidisciplinary way, with a particular interest in the study of corporal language, focused on various aspects of expression and consciousness, including their relationship with digital media. Her experience with dance began in her childhood and has, ever since, been the central guiding point of her career in the visual arts. A pioneer in the so-called computer dance field and multimedia performance, the artist began to use the computer as a tool for understanding artistic processes as early as 1973, when she became Brazil’s first video artist with the work M3X3, which already foresaw the representativity of information technology in the everyday life of society. In 1981, she created the Nota-Anna software, an application for transcribing the body’s motion, resulting in scientific analyses for the tracing of corporal movements. Analivia’s investigation works with the organic/artificial duality in body language and, in parallel, the control/freedom duality in its relationship with technology, considering corporal language as a semantic filter for reality, an intermediary for dialogue with the public. This has led to her innovative productions in both art and technology, which kindle multisensorial experiences and also work with health, affectivity and self-knowledge , dialoguing with technology, art, the body and the mind.

 

Analivia Cordeiro holds a BA in architecture from the Faculdade de Arquitetura e Urbanismo of USP (1976, São Paulo), an MA in multimedia from Unicamp (1996, Campinas-SP) and a PhD in communication and semiotics from PUC (2004, São Paulo-SP); she has furthermore done postdoctoral work for the Universidade Federal do Rio de Janeiro (UFRJ, 2010, Rio de Janeiro) and for the Universidade de São Paulo (USP, 2018, São Paulo). Between 1977 and 1979 she studied contemporary dance and choreography at Merce Cunningham Dance Studio in New York and at Alwin Nikolais Studio. Recently, the artist featured her first major solo international exhibition, at the ZKM - Museum of Contemporary Art (2023, Germany) and Centro Atlántico de Arte Moderno, Las Palmas (2023, Spain), besides participating in a show at LACMA (2023, USA). The shows and events in which she has participated notably include the 1973 International Festival of Edinburgh; the 12th Bienal de São Paulo (1974, São Paulo, Brazil); LatinAmerica 74, at Institute of Contemporary Arts (1974, London, GB); International Conference Computer & Humanities/2, at the University of Southern California (1976, Los Angeles, USA); Art of Space Era, at Von Braun Civic Center of Huntsville Museum of Art, 1978; Brasil Século XX, Bienal de São Paulo (1984, Brazil); Arte e Tecnologia, at Itaú Cultural (1996, São Paulo, Brazil); the 27th Annual Dance on Camera Festival (1998, New York, USA); SIGGRAPH (2008, USA), B3 Biennale of Moving Images – Expanded Senses, at Museum Angewandte Kunst (2015, Frankfurt, Germany); Video art in Latin America, Laxart (2016–2017, Los Angeles); Radical Women: Latin American Art, 1960–1985, at Hammer Museum (2017, Los Angeles, USA), Brooklyn Museum (2018, New York, USA) and the Pinacoteca de São Paulo (2023 and 2018, São Paulo, Brazil); Coder le Monde, at Centre Georges Pompidou (2018, Paris, France); and Control and Chance: Art in the Age of Computer, at Victoria & Albert Museum (2018, London, UK), Electric Dreams: Art and Technology Before the Internet - TATE Modern (2024, London, UK), além de Radical Software: Women, Art & Computing, 1960-1991 - The Contemporary Museum of Luxembourg - MUDAM (2024, Kirchberg, Luxembourg) Her work figures in important collections, including those of the Museum of Fine Art, Houston (USA), Victoria & Albert Museum Collection (GB), the Museum of Modern Art of New York (MoMA-NY, USA), the Museo Nacional Centro de Arte Reina Sofia (Spain), the Museum of Concrete Art (Ingolstadt, Germany), MAC-USP (Brazil), the Pinacoteca do Estado de São Paulo (Brazil), Itaú Cultural (Brazil), and the collection of Oskar Schlemmer (Switzerland/Germany). Among her various activities, the artist is a member of the International Dance Committee (IDC), of UNESCO.

Based primarily on principles of social collectivity and ethics, in 1954 Geraldo de Barros created the cooperative furniture factory Cooperativa Unilabor, a unique venture that combined functional design and modernism with an innovative approach to collective production. Both Unilabor and Hobjeto, another factory he established in 1964, became known for innovation in furniture design and production processes.

 

Barros’s aim to democratize design and art led him to explore possibilities for creating works that were easy to produce and more accessible. To this end, in the 1980s, the artist created a series of works in Formica to be manufactured at the Hobjeto furniture factory. Both the furniture and the Formica works, also known as object-paintings, were made using the same techniques.

 

His deep study of colors in Formica gave rise to the unique series of 55 inseparable pieces called Jogo de Dados, first shown in 1986 at the 42nd Venice Biennale. In 1989, this series was presented at Unicamp (which currently holds the series in its collection) and at the Museu de Arte Moderna of São Paulo (MAM-SP). This body of work, from which the series Da retomada de alguns objetos-forma da arte concreta also derives, was conceived to be produced by the Hobjeto furniture factory and follows the concept of the golden ratio, a mathematical principle widely used by Renaissance artists that governs natural growth.