How did Baroque mural painters make walls and ceilings seem to dissolve into open space?

Baroque mural painters achieved the illusion of walls and ceilings dissolving into open space by integrating painting, sculpture, and architecture into a unified, dramatic ensemble. This effect was primarily realized through the following techniques:1

• Sotto in su: This technique involves the extreme foreshortening of figures painted on high surfaces, creating the visual impression that the figures are suspended in the air above the viewer.2
• Illusionistic Perspective: Artists blended painted scenes with the actual architecture of the building to create a seamless, endless illusion of space. By using complex compositions that surged along diagonal lines, painters moved away from the stable, defined space of the Renaissance toward a dynamic, theatrical vision.34
• Integration of Elements: Baroque artists often allowed painted figures to "burst" out of their frames, flooding over architectural elements like gilt stucco to merge the painted scene with the physical space of the room.5
• Lighting and Color: The use of vivid colors, dramatic light and shade, and hidden light sources heightened the immediacy of these scenes, directing the viewer’s senses toward the infinite and the heavenly.14

These methods transformed static surfaces into expansive, immersive environments that invited viewer participation.1