The MATRIX drawings are an attempt to draw inner space, rather than represent an object as perceived in space:

"This type of perspectival rendering, where parallel lines do not converge, is often used by architects to give a solid-looking three-dimensional view of a structure. By extending the orthogonal lines to the edge of the page and sometimes multiplying the perspectival matrix with paler lines around the figure, Gormley has reversed that effect so that the depicted sculpture seems to vibrate and lose determinate boundaries."

Extract from 'Sculpting Darkness' by Margaret Iversen, ROOM, London: Corbin & King, 2014, p. 78