Veronese, The Dream of Saint Helena, ca. 1570. Oil on canvas, 78" x 46."
In Paintings I Like pt. 45, I pointed out just how much mileage Veronese could get out of a deceptively simple pictorial device; in the case of the Alexander picture in that particular post, it was two interlocking waves of value, dark on the bottom, light on top.
In the Dream of Saint Helena, He harnesses two of picture-making's most basic truisms to great effect. Horizontals and verticals give a picture stability and sturdiness; the refer to both architecture and the picture's own framing edges. Diagonals suggest motion, and make pictures feel alive and dynamic.
Veronese gets the full benefit of both with the reversed "L" of window, and the flying "X" of the cross. The two separate motifs are reflected in and connected by Helena: her straight back and left leg mimic the architecture, and her right leg, right arm, and neck pick up on the diagonals of the cross.