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Let's talk about the distortion nodes and what they can do to an image or a portion of an image, to add special effects or to offset them, and all sorts of neat things. So let's start going through it, I have prepared this example here to show two things. One is to show each of the distort node of course, and then I also how to combine them, and make them into a processing chain, so that you can achieve whatever effect you want. So we are starting out with this picture of me in my cowboy hat, we can thread this to a viewer by adding an output viewer, and you can see that it's me in my cowboy hat centered.
If you drag over it, you can see that I have already masked this image by constructing a 3D Bezier curve to make a mask. So it's Alpha zero, in this is really cruddy background, and then Alpha 1, where I am. So the first thing we want to do is the Flip node. The Flip node flips an image, left to right. So we can go in one way, and then just flips it along the x-axis that way. They can also flip it along the y -axis, and turn me upside down. Or flip it both ways, x and y. We are going to flip with x, just to make me face the other direction.
Next step is the Rotate node. The Rotate node takes the image and it rotates by the number of degrees, in this case, 5 degrees, and it rotates it counter clockwise. So more degrees, rotates to the left, the less degrees, rotates to the right. You can rotate 90 degrees if you want to flip an image on its side, or in this case, taking 5 degrees just to rotate it a little bit, just to even square my face up. Next up is the Crop node. The Crop node takes any portion of the input image, and then based on an area in pixels, now the compositor works in pixels, it does pixel math effectively.
So what it does is it crops the image that's input, and puts out an image that is the size of the bounding box, the bounding box is defined by X1, Y1, which is your lower left hand corner, and then X2, Y2 is your upper right hand corner. So that takes this image that comes in and then just crops out the stuff that I don't want. If we crop image size, then it resizes the image to match the respective output. So after we do all that to the image, now we come down here and next up is the Scale node within the Distort Group.
The Scale node takes an image and scales it up or down. In this case, I'm scaling it 1.4 in the x -direction, and 1.5 in the y-direction. It can scale in both Relative Mode, which is what you saw or in Absolute Mode, if I want to absolutely make this image a certain pixel size, then I can click absolute. When I do that, Blender goes out to my current format settings over here, SizeX and SizeY, and pulls those in, and it assumes that it wants me to rescale this image to fit the normal output.
I don't have to do that, but usually you do. So we are going to go ahead and set that back to 1.4, and with all of these, as with any Input node you know, you can click and enter the number, and then just press Tab to get to the next field. I'm going to set the Y to 1.5, just to make me look a little thinner. Next up, we have the Translate node. The Translate node takes an image, and shifts it, left or right, based on the X, and up or down based on the Y. So in this case, I have shifted it to the right and down a little bit, and that's what the Translate node does.
So now that I'm shifted left and right, we now come down to the background, so that's my foreground, so I'm going to be in the foreground. Now let's talk about the background a little bit. Here we have a desert image loaded up. It should load up if you press E or F12, or Mac users, just click the Red new button that I have conveniently put up here for you. The Lens Distortion node takes an image in and distorts it. Now, what kind of distortion can it do? Well, a lot of different kinds of distortions actually. One is it can make a projector kind of distortion, which flattens out the image.
The other is it can jitter around, and jitter the pixels. And then dissimulate different kinds of lenses that are used in cameras. You have the Distort and the Dispersion settings. As we increase the distortion, we get more of a rounding effect around the outside, almost like it was shot with a fisheye lens. If we go negative on the distortion, we get the opposite kind of effect, and I remember seeing this effect, I was just watching a movie about a rider that was in rehab, and when they did the individual shots of the people, they used this distortion, and it really draws your attention into the middle.
I have also seen this used in a couple of CG animated movies, where the guys start speeding up, or starts focusing, or turning into a werewolf and things like that. So a little bit of distortion adds on to the effect that this was shot through a real lens, or enhances the effect, dispersion does chromatic smearing around the edges. So really, really bad lenses will actually bend the light and absorb different color and spectrums around the outside, and so that's what dispersion does.
We'll go ahead and set that back to zero. So those are the kinds of lens distortion you can do with Blender. Next step is the Set Alpha node that just simply sets the Alpha value of an image. If you fed this with the Alpha value of a mask in 3D, and fed a normal image, then this would be applying that alpha, and replacing the alpha channel of the image with the Alpha channel that you have supplied. Next step is a really cool node, called the Displace node. The Displace node displaces the pixels according to a texture, and I'm going to go ahead and crank this up, so you can see what happens.
Based on the value of the texture, it takes the pixels and stretches them in whatever direction you've specified in the number of pixels, in the x and y direction, based on the value of this texture, and this is a simple wood texture that I have created over in the Material side. Now you can also notice that these are sockets, so you could hook up either a Time node to a multiply, which we'll get into a little later, to Create and take this value from zero to something like this number over time, and then that will the distort and make this into a kind of a crazy kind of a fade, I have seen used in video.
So we are going to set this back to something a little bit more modest to simulate the effect of heat coming up. If you would ever want to simulate the effect that heat waves in the air have on distorting a lens or a picture, then you want to use this Displace node. So now that we have displaced and modified the background image a little bit, we use our AlphaOver node to combine me and the foreground Shifted and Displaced over a background.
And so that's the little noodle that you would do to create a Composite image based on the background plate, and a foreground.
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