https://www.nma.art/videolessons/perspective-for-the-rest-of-us-auxiliary-perspective/?course=677610

Many artists are intimidated by the complexity of linear perspective. In this video series, instructor Sheldon Borenstein shows you a friendly and simple approach to perspective. In this final lesson in the series, Sheldon will focus on auxiliary perspective, which is vital for drawing anything at an incline or oblique angle. You will learn: how to create a grid of your drawing, find your false and true horizon lines, where to place your vanishing points, and how to determine lighting. Sheldon will then apply these concepts to a drawing of an outdoor stairway on toned paper, using a brush pen, marker, and pastel pencil.