Final answer:
Johannes Vermeer advised artists in his treatise on painting that paintings should look like illusionary windows. Vermeer used complex layers of paint and forced perspective to achieve a sense of depth and create a quiet and timeless atmosphere in his works.
Step-by-step explanation:
The artist who advised artists in his treatise on painting that paintings should look like illusionary windows is Johannes Vermeer. Vermeer used complex layers of paint to achieve a pearly light that envelopes his subjects, and his forced perspective creates a sense of depth in his paintings. The quality of light in Vermeer's works creates a quiet and timeless atmosphere, giving the impression that the paintings are like looking through a window.