But I've been thinking a lot about the geometry used in classical art that defined the composition. The classic masters did use it. Learning how to draw a root2 or phi rectangle doesn't create a beautiful painting in itself, it does help us with proportions that can be used like a template to suit and support the original concept of the painting. Graphic design uses templates for columns and page layout, so why not fine art painting.
This youtube video may be a bit overstated with all the triangulations, but I do think it makes the point that the old masters used geometry in their work - sacred or not.
Note: These lines are only to show points of interest in the overall two dimensional picture plane, and not intended to suggest perspective for a three dimensional illusion. Perspective and its lines of delineation are a separate area of study.