How To Match Perspective
I'm gonna go and open up the first file that I'm gonna show you guys today, which is this one here. And this file deals with perspective, which in my opinion is the most important thing that you have to think about when putting images together. Now a little caveat. When you're compositing, you either shoot your own photos or you use photos either from previous shots or stock images. For the examples that I'm gonna show you today, I'm mainly gonna focus on images that were not intended to be used as a composite, so maybe stock photos or different photos that you shot in the past, but you really didn't have that intention of putting them together, 'cause that's when the real problems arise. If you're shooting the photographs yourself then you can think about perspective and all that sort of stuff as you're shooting with the camera. So what I want to do is just show you the different things you have to think about when you grab images from different places and put them together. So in any...
scene that you work with, you usually have a ground plane and you have a sky. And right off the bat I'm gonna tell you the most important thing when you're compositing is you need to know where those two things are. Where your grand plane is and where your sky is. And wherever those two meet, that is your horizon line. In this example here we can see all these lines leading to this gray line going across the center. That is your horizon line. You might have also heard the horizon line referred to as the eye level. So that little graphic there is just a little person's head and you can see the eyes there and that will be you standing and looking out into maybe a beach or a desert or something like that. But when we are talking about compositing in photographs, we're talking about mainly where the ground meets the sky. So I have this composite there. Now it may look okay at first, but then the longer you stare at it the more you realize that something is wrong with it. And you may not know exactly what it is, but if we zoom in you can see that the mask looks okay, there are shadows on his feet, there's even mud on his shoes, but somehow the composite just doesn't feel right. And that's what I was talking about earlier, there's a feeling that you get when things are not working. And in this case, obviously it's the perspective, but before we go into fixing the perspective of this image, I'm gonna show you a little bit more about how perspective works. So I have these little diagrams here and I'm gonna talk about different types of perspectives that you'll encounter. We have the one point perspective, which, in this scene here, we just have these cubes, they're all in perspective. And the thing that I want you to notice is that all converging lines lead to the horizon line and they meet at what's called a vanishing point. So let me open up this group here and I have the vanishing point there. So notice how all the converging lines from those boxes that are sitting on the plane lead to that one vanishing point. So vanishing points are always on the horizon line with one point perspective. And even if we didn't have the background plane, we could determine that, and this is really important to know when you're compositing because sometimes you may have maybe a photo of a car on a white backdrop and you can't really tell where the horizon line would be, but if you follow those converging lines, you can determine where that is and then in a moment I'll show you how to composite something in together when you know where the horizon lines are. There's also a two point perspective. So you can think of this as standing maybe in the corner and looking right at a building and then you take photo, and then you have the sidewalk on one side and then you have the sidewalk on the other. And that's what two point perspective would be in, let me turn on the converging lines here so you can see. Vanishing point is here, vanishing point is there, and if I enable the background, that's where the horizon line is. Then we have three point perspective, which has the two vanishing points but also has a third, so that what you can think about this is maybe you're taking a photo of a building and you're looking up. Or if I were to flip this image vertically, then it would be sort of like flying over a building and looking down, and let me actually do that so you can see what that looks like. I'm gonna go into image rotation, flip canvas, vertical. And you can sort of see how it looks like we're flying over a building and looking down. So that's what three point perspective would be. So now if I go back into the one point perspective and let me enable, or disable that there. So I'm actually missing a file, no I'm not, here I am. So you might be thinking when you're looking at a graphic like this, well what happens when you rotate a box, wouldn't that change the vanishing points and converging lines? Yeah, that would change. But the vanishing point would still be in the horizon line. So no matter what subjects you bring in, they always have to, the horizon lines always have to match so that the objects appear in perspective. That is of course, you're assuming that everything is sitting on the ground. If you have something that's flying or floating of course that really wouldn't matter. So in this case here we're gonna composite this cube in and let me just disable that layer there, so I have this cube. And notice if I move this cube up this high, it already doesn't look right, it doesn't feel right. If I bring it down low we have the same problem. But if we draw those converging lines and see where they meet, that's the vanishing point there. So if I align that on the horizon line. You can see how now it looks like it fits into the scene, and I can actually even scale it in perspective, so I press Command + T, that's Control + T on the PC to bring up these handles, and notice this little pivot point here, I can click and drag on it and I can also hold option. That's Alt on the PC, and I can click anywhere I want. And what that allows me to do is to rotate from that pivot point, or scale into that pivot point. So I'm gonna hold Shift + Option click on a corner handle and drag inwards. So notice how I'm scaling into that pivot point. So what I'm gonna do is I'm gonna scale in perspective. So you can grab that pivot point and drag it anywhere on the horizon line, so I'm just gonna place it there. And I can hold shift, option, click and drag, and now I'm scaling in perspective. Notice how it looks like this box is going further into the background and coming right in towards us. So these are sort of the things that you have to think about when you're placing images together in PhotoShop. You simply can't just throw something in and just, I mean sometimes you have to eyeball it, but most of the time you really have to be conscious of how perspective works in a scene so that it feels right. So, now let's look at these boxes here. Also, once you define a horizon line or you know where that horizon line is, you can use, you'll know that anything that's below the horizon line, you won't be able to see the bottom part of. So look at these boxes here, we can't see the bottom of these boxes that are below the horizon line. If it's above the horizon line then we can't see the top. So you can use that knowledge to composite when you don't have a background. So I know there's no background to this car because it was marked out, but maybe if this were a stock photo or maybe even a 3D model or something like that that was rendered out, you don't have a background that's in a white backdrop. You really wouldn't know where this car belongs in this scene unless you start drawing those converging lines and sometimes that can be a little tedious and take some time, but if you imagine this car as one of these rectangles then you can sort of know where the horizon line is, you can see the top of this car just a little bit. So if I enable these boxes, which of these boxes resembles the car the most? This one here. So if I click and drag the car down to roughly this position here, you'll see that the car now fits within the scene. If I click and drag it up, it no longer fits. So again, perspective is really powerful when you're putting images together. A lot of times you may have masks that are not that good, the color may not match, but as long as you get the perspective right, it really helps bring those composites together. So I'm gonna quickly show you this graphic here. These are 3D models that were created to match the perspective of this scene. You don't have to worry about how this was done, but just know that these 3D models are in perspective and when you're compositing people into a scene we have to realize that if you have two subjects that are roughly the same height, the horizon line will cut them in the same part of their body, so for example, this man walking here, you can see the horizon line is cutting him just above the bicep below the shoulder. That will be true no matter how far back he is. Notice that even this guy way back here, the horizon line cuts him in the same place. This guy here is looking down and he's squatting and notice that there's a space between his head and the horizon line and the same will be true no matter how far back he goes. Even this guy way back here there's some space. And we can keep pushing him back further and further and further until he's just the dot just right below the horizon line and at that point it really wouldn't matter if he was directly on it. Obviously that would change if the subject was standing on something or was not sitting flat on the surface. In this case the woman is standing on this cube so therefore our horizon line wouldn't cut her in the same spot. So we're back at our example. How could we fid the problem that this image has? Let me show you what the original image looks like. The image of the man. He's standing over looking at a lake. Notice where the ground plain meets the sky, it's right here. There's the ground plain which is the sand and the water, the sky is here, it meets on this line which is right above his knees. Notice where the ground plain is here and where the sky is, it's right here. So that's why you're getting that feeling that things don't work, the perspective is not right. So we can do one of two things. We can click and drag him up, notice that as soon as I do that, even though you can't see half his body, the image already looks much better, it feels better. I'm gonna undo that and I'm gonna click on the beach layer, and I'm gonna click and drag that down and just place the horizon line right above his knees. And notice how that immediately feels and looks much better. So these are the things you have to think about when you're compositing. Also, I'm gonna show you a different background, we have this city. And notice that the horizon line of the city is back here, we have the ground plain here and the sky here, and they meet right about here. It's right above his knees and it looks in perspective. If we were to drag this up it no longer looks in perspective. I know we don't have the floor back here, but you can imagine that it still doesn't work just by looking at it. So that is how important perspective is when you're compositing. Now even though you may get the perspective right, it doesn't always work. Sometimes images just have perspectives that are vastly different. So for example in this case, we don't even have to draw the converging lines to know where the vanishing point and the horizon line of this train image is, we can just see it. We can just see it. You can see all of these converging lines, the train tracks, the train, the yellow line, everything leads to a point roughly here in the center. So we know that that's where the horizon line is. So if we enable this layer we know where his horizon line is, it's right above the knees, so I'm gonna click on his group and drag him up there. He's in perspective but he now looks like a giant. You might be thinking well, can't we do that little trick you showed us earlier with the pivot point. Let's try that, click and drag that pivot point over roughly where the horizon line is. Hold Shift, Option, that Shift + Command, Shift + Alt on the PC, excuse me. Click and drag, and yeah he's scaling in perspective, but he still looks like a giant, and that's simply because the two images have vastly different perspectives so you can't always fix the perspectives. So you either will have to cheat and bring him down and hope that it doesn't feel that bad, or just use a different foreground or a different background.