Victorian House Set Extension with Projection Man: Camera Calibration

Photo of Joseph Herman

Instructor Joseph Herman

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  • Duration: 07:16
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In this video we will calibrate the camera's in the scene.

You'll start by making the Photograph's aspect ratio 16 X 9 and proceed to calibrate the camera utilizing Cinema 4D's Camera Calibrator tag. This will allow you to draw lines that define the X, Y and Z axes as well as set the origin of the world.

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Transcript

- In this video I'll show you how to calibrate a camera to the photograph which will eventually be used as a projection camera. Okay, here we are in Photoshop, that's where we'll start. This is the picture we're going to use of this Victorian house and the first thing we're going to do is check the dimensions. So let's go ahead and look at the pixel dimensions of this image, 2272 by 1704. We're gonna change the width to 3029, which is going to give this image a 16 by 9 aspect ratio because that's what we're going to be working in. So let's go ahead and save this image and switch back to Cinema 4D. We're gonna start by baking the new camera and then what we're going to do is we're going to click on the render settings for this and make it 1920 by 1080 which is a 16 by 9 aspect ratio. Next what we're going to do is we're going to right-click on the camera and give it a camera calibrator tag and we're going to bring in that picture that we just saved, and there it is and it's at the right aspect ratio and we're ready to start calibrating the camera to this image. So the way the camera calibrator works is that we can drag these lines here so that they match the X, Y and Z-axis of the image. So Z goes in and out, X goes left and right and Y goes up and down. So we'll be dragging this one, this line here that we created, to the Z-axis. The way you get it to be the Z-axis, you Shift click the line and you notice that it changed different colors. When it hits blue, it means that it's indicating a Z-axis orientation. So we've made another line here and notice when you drag it in you get a little magnifying area which helps you when you're dragging it in. Next, we'll add another line and we'll add even a third... you could get by with two lines for the axis, but sometimes it helps if you do more. So here's another Z line, Shift click it, so now all these lines are blue and if you look over down into this area here you'll see that the Z vanishing point is now solved. Green means solved and red means that it's not solved. Let's add another line and let's go ahead and make a X-axis line here. Here we go, we'll Shift click that so it turns red since X means red. You can copy a line by holding down the Control key and dragging the line to a new position and then you can adjust it as you see fit, so there's another X line. You notice that a lot more of the vanishing points have been solved, some of them are yellow, yellow also is okay, what you don't want is red. So there, we're creating another X line here and it says that the X vanishing point now has been solved. The Y vanishing point it says indirectly solved, but we might as well go ahead and create some Y lines as well. So let's create one here along this edge on the side of the front of that part of the house, so we'll drag it in, okay, and then will Shift click that until it turns green. Let's go ahead and create another line and we'll drag it to another Y area, let's say over here. Okay, and after we drag it, we'll Shift click it so it turns green. Now while everything says solved, I'm going to add some more lines anyway for the Y since I find that the more lines you have often the better results you get. Some of it has to do with the quality of the picture and the way you do it, so your results may vary somewhat. So we're making another Y line here, Shift click it, and I'll make another one. So we'll do this one on the side of this window here because that's a nice little Y line that I can do. There we have it, we'll Shift click that, and there we go. Everything you see is pretty much solved except for this thing, it says the camera position. Okay now, how do we figure out where the camera position is? Okay we've got the vanishing point set, but we need to tell it where the camera is so I'm gonna create another Y line here and I'm going to put the bottom of it right where I think the floor should be. Now if this bush wasn't in the way, it be easier to find where that floor position was, but since we don't know exactly where the floor is, I'm just gonna give it my best guess. Now what I'm going to do is I'm going to click this known length button and I'm going to estimate that length. This will give our scene a sense of scale, so I'm gonna say that it's like maybe 13 feet. You don't have to be perfect, if you know exactly what it is, then that's good. So now I'm gonna click the add pin button. The add pin button adds this little circle into the scene, which I'm going to drag to the bottom of that line, and now what I've done is I've solved the camera position and where that little bottom of that line is now is going to be the center of the world. I'm gonna make a cube and you'll notice that as soon as I make the cube the image behind it disappears. I could solve that by making a background object and then clicking off of the camera calibration tag and then you'll notice that you can see the image and the cube. So you'll notice that this cube now is now correctly aligned to the world; you can see that if I move it around left and right, up and down, it looks like it's in the scene. So we know now that the camera is properly calibrated to this scene. In our next video we'll start building the low resolution geometry of the house.
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