Lines are all the same until one has some extra weight. Now, there's not much mechanically different about the last words in this sentence, except that it's written in bold. And in written text, it's hard to miss a word that's written in bold. So, if you were to think about written words as if they were a line drawing, because words are just that, they're lines. And bold and italic are ways to add extra information to those same letters. You're not adding any extra words in to communicate that weight means more in this sentence. You're just thickening them up, and in a sense, adding more information to that word. In a drawing, the same is true about lines. And you can see it in a difference between these two eggs. They're exactly the same shape. But the one on the right has uniform line weight all around. It's kind of boring. If you were an animator, this would be ideal, because it's easy to keep consistent. But otherwise, this is as simple as a line gets, and you can do a lot more with it. The one on the left, however, has very thin lines and also very thick lines. And somehow it seems to have more volume to it, a little bit more like a light source. That's exactly what these lines are saying. This is indicating that the eggs being illuminated from the top down, and so up top where it would be brighter, the lines are thinner, to indicate sort of a lighter value. But then at the bottom, the lines are thicker, and this gives it sort of a shadow information. So in this way, I haven't changed the shape, but the lines tell more of a story. Line weight can tell the viewer a lot of things, but in this video, I'm just going to focus on two simple ones. First, lighting. So here you can see I've got a couple objects and a light source. That's what those arrows pointing down from the sky are. And you can see that I've used heavier lines where there'd be a little thicker shadows. So with these inset plates here, you can see that the bottom side, the side that recedes from the light, has sort of a weightier line to it, and that's on purpose. Also these rivets would be deeper inset into those plates than some of the thinner, embossed light relief lines. And so they're darker as well. So this is really still a line drawing, but it definitely gives lighting information just from the weight. And it doesn't need to be super clean for this to work either. If I wanted to do a quick sketch, adding to this existing drawing, say like a little hockey puck thing, I could use thinner lines here, and then maybe a thicker line where it's sitting on the ground. This is because there's a bit of a footprint, sort of a soft shadow at the base, and they probably have a darker edge over here, again, furthest away from the light source. And then I could erase away a bit where it would be more illuminated. And that might have a bit of a cast shadow as well. But it's still a line drawing, and yet it tells more of a story. And secondly, depth. You can use the line weight in a drawing to indicate some of the perspective distance at work. So see all these floating circles? This composition somehow indicates that a few of those circles are far away in the distance, and a few of them are right up close to the viewer. Well, one of the key ways you can see that is that the lines are very thick and very heavy on the foreground objects, and then very fine, very thin in the background objects. Without any extra rendering, you can really empower a line drawing by using line weight to help inform the viewer. You're just giving him a few extra clues, since you're drawing lines anyway, you might as well consider how thick they should be. So thanks for watching, and if you like the videos, make sure to tell some friends about the site. I need your help to spread the word. Thanks guys.