quadratura

Quadratura is a term introduced during the Baroque period to describe simulated architecture. This technique unites architecture, painting and sculpture, leading to an overwhelming impression of illusionism. The artist would paint a feigned architecture in perspective on a flat or barrel-vaulted ceiling in such a way that it seems to continue the existing architecture. The perspective of this illusion is centered towards one focal point. The steep foreshortening of the figures, the painted walls and pillars, creates an illusion of deep recession, heavenly sphere or even an open sky.
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n. squaring

n. quadrature, the process of making something square