There’s a concept that gets covered pretty extensively in art classes called negative space.
Negative Space is the space around what you drew. In an ink drawing like this one, well, it’s the white area. There’s also positive space, which is what you drew, the black part. Most people don’t even think of the white space as part of the drawing, but it’s just as important as the rest.
There’s a lot of interesting things you can do with negative space, but the most common one is to imply that a line exists when it doesn’t. If you look at the top of the window on this door, you can see that the line marking the top, well, is barely there. And, of course, the texture of the glass is more implied than shown.
It was that texture that made me stop and make this sketch. This door exists in the studio arts building at the university I attended, and I walked past it hundreds of times while getting my degree. And one day, I had some extra time, and I saw the interesting way the glass texture was lit, and I found what to do with my time.
This was one of the first drawings I’ve done working in pen without any guiding pencil lines, so there are a lot of wobbling lines where there should be straight, and the door isn’t exactly a rectangle. But I managed to get that texture right, with the odd backlighting and everything. And that is what I was going for.