Architect: Pierre Chareau; Paris; c.1930. The gentle angle creates a sense of elegance and flow on the stair. Each part is subtly distguished from its neighbour.
Architect: Haroaki Ohtani; Kobe, Japan; c.2006. This stair is the only means by which you can move from one space to the next. The experience of circulation is always a vertical experience. The treads are wide and deep enough for each to be a habitable space in itself.
play around with a range of line weights, hatching effects, etc. to explain what materials you might be thinking of. then use the section as the start point for your 3D model in sketchup.