TIP 6/10: Sloped Roofs in Perspective

Sketching Tip #6:  Sloped Roofs in Perspective

Sketching a sloped roof, or any sloped surface, can be a real challenge. I pretty much always draw lines down the slope of the roof so that the angle of the roof reads, no matter what the roof material is. The clearest way to understand this is to look at tile roofs with ridges and valleys, like this one at Brunelleschi's  Pazzi Chapel in Florence in this classic, one-point perspective view.

Step one is to find the vanishing point and your eye level for most of the parallel horizontal building and ground lines. My eye level line was very low, close to the ground, and the VP just to the right of center.

To draw the slope of the roof correctly, the first line I draw on the sloped roof is a true vertical line (in yellow) directly above my vanishing point at eye level... yep, straight up and down right over my vanishing point! 
Then, I know that all the ridges and valleys to the left of this line angle in one direction, and all the lines to the right of this vertical line angle in the other direction. The farther the line is away from my vertical, the flatter the angle.  I usually eye-ball this. 
Take a look...

So what is really going on here? Remember that lines that are parallel to each other converge to the same vanishing point, so since the roof is angled, it goes to its own vanishing point in the sky...

Remember this tip: 
if a surface tilts UP and away from you, the Vanishing Point also tilts UP.
The part that most people don't realize is that the vanishing point for the slope is directly over your eye level vanishing point!!

This principle is also true for 2-point perspectives, but it's easiest to see in a 1-point view.

Look at this view from Florence and see if you can find the vanishing point and how I drew the tile roofs!