visual
the answer is overlapping
Many artists use a technique called 'start-with-rectangle-and-round-the-edges'this creates a near circular people most modern-day people call an oval. We are not sure of the scientifical name of an rounded-edge rectangle, but one thing is for sure, it is not a quadrilateral because not all four edges are present.
cubist
Some items from the Official MC Escher website: Maurits Cornelis Escher (1898-1972) is one of the world's most famous graphic artists. His art is enjoyed by millions of people all over the world, as can be seen on the many web sites on the internet. He is most famous for his impossible structures, such as Ascending and Descending, Relativity, his Transformation Prints, such as Metamorphosis I, Metamorphosis II and Metamorphosis III, Sky & Water I or Reptiles. But he also made some wonderful, more realistic work during the time he lived and traveled in Italy. Castrovalva for example, where one already can see Escher's fascination for high and low, close by and far away. The concept and name was even used for the basis of a Dr Who episode. The lithograph Atrani, a small town on the Amalfi Coast was made in 1931, but comes back for example, in his masterpiece Metamorphosis I and II. M.C. Escher, during his lifetime, made 448 lithographs, woodcuts and wood engravings and over 2000 drawings and sketches. Like some of his famous predecessors such as Michelangelo, Leonardo da Vinci, Dürer and Holbein, M.C. Escher was left-handed. He was influenced by the Alhambra in Spain.
Artists didn't need to use perspective or create the illusion of depth.
The use of perspective, linear and atmospheric, create the illusion of depth. As objects recede into the background they appear 'more blue' and have less detail. This technique can be seen in the background of the 'Mona Lisa'.
Chiaroscuro is the use of value contrasts to replicate dimension. Artists make the lightest parts of a subject white, and the darkest shadows black. It is an illusion technique which helps 2-dimensional art portray 3-dimensional subjects.
Artists use location to direct the viewer's eye.
Stippling
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Caravaggio
By using different shading techniques such as chiaroscuro
They used darker bolder colors in the difference.
they are people who make pictures that make peoples eyes boggle.
MC Escher uses mostly patterns in his work and is one of the most famous artists for using this technique.
Cave painting artists used a form of perspective by depicting things closer to them larger in size, while things farther away were smaller. This technique gave the illusion of depth and distance in their paintings.