1 00:00:00,000 --> 00:00:03,990 The Aim constraint is another important constraint that we use in 2 00:00:04,000 --> 00:00:04,990 character animation. 3 00:00:05,000 --> 00:00:08,990 And it allows one object to be aimed at another. 4 00:00:09,000 --> 00:00:13,990 You may have encountered the Aim constraint when doing lighting and rendering. 5 00:00:14,000 --> 00:00:20,990 It's used often to aim a light at an object or camera, so that the camera or the 6 00:00:21,000 --> 00:00:23,990 light will follow an object through the scene. 7 00:00:24,000 --> 00:00:28,990 We can also use Aim constraints in character animation to position things such 8 00:00:29,000 --> 00:00:33,990 as the eyes, to make the eyes point at a specific locator. 9 00:00:34,000 --> 00:00:41,990 So in this scene, I have two eyes and a single locator here that we can use as an aim. 10 00:00:42,000 --> 00:00:45,990 So let's take a look at how to set up an Aim constraint for the eyes. 11 00:00:46,000 --> 00:00:51,990 I am going to select my locator first and then Shift+Select eye right. 12 00:00:52,000 --> 00:00:54,990 Remember, the constrained object is always selected last and it should be 13 00:00:55,000 --> 00:00:57,990 highlighted in green. 14 00:00:58,000 --> 00:01:00,990 And then I am going to go over to Constrain > Aim. 15 00:01:01,000 --> 00:01:05,990 Now in these options, we have Maintain offset, which allows you to basically 16 00:01:06,000 --> 00:01:09,990 maintain the initial position of the eye. 17 00:01:10,000 --> 00:01:15,990 We also have the Aim vector, and that is along which axis is this aiming? 18 00:01:16,000 --> 00:01:20,990 Is it aiming along X, Y or Z, or a combination of any of those? 19 00:01:21,000 --> 00:01:24,990 And then also, you know, what is your up vector for the object? 20 00:01:25,000 --> 00:01:29,990 In other words, it's aimed at an object, but also how is it rotated along that axis. 21 00:01:30,000 --> 00:01:34,990 World vectors as well, and then of course, along which axes we want to constrain. 22 00:01:35,000 --> 00:01:40,990 Now in this case, I'm just going to go ahead and click on Maintain offset, and 23 00:01:41,000 --> 00:01:42,990 let's go ahead and add that, so we can see how that works. 24 00:01:43,000 --> 00:01:47,990 And when we do that, basically nothing changes, and the eye just stays in 25 00:01:48,000 --> 00:01:53,990 place and now we can go ahead and move this and you can see how it kind of 26 00:01:54,000 --> 00:01:56,990 moves to match the locator. 27 00:01:57,000 --> 00:02:01,990 But if you notice here because we set maintain offset, it's actually not looking 28 00:02:02,000 --> 00:02:02,990 directly at that locator. 29 00:02:03,000 --> 00:02:06,990 It's looking a little bit to the side. 30 00:02:07,000 --> 00:02:11,990 Now this can be very handy if that's what you want, but let's go ahead and do 31 00:02:12,000 --> 00:02:14,990 this a little bit more precisely. 32 00:02:15,000 --> 00:02:17,990 Let's go ahead and delete this constraint and re-create it. 33 00:02:18,000 --> 00:02:22,990 Probably the easiest way to delete a constraint is to go into the Outliner, find 34 00:02:23,000 --> 00:02:27,990 the object Eye_Rt, which has a constraint, and you will notice that the 35 00:02:28,000 --> 00:02:29,990 constraint is underneath the object. 36 00:02:30,000 --> 00:02:35,990 So all we have to do is select that and hit Delete, and that gets rid of the constraint. 37 00:02:36,000 --> 00:02:39,990 So now when I move this, the object does not constrain. 38 00:02:40,000 --> 00:02:42,990 So let's go ahead and re-create this constraint. 39 00:02:43,000 --> 00:02:47,990 So again, I'm going to select the locator, Shift+Select the eyeball, again, the 40 00:02:48,000 --> 00:02:52,990 constrained object is last, go into Constraint > Aim constraint, and let's go 41 00:02:53,000 --> 00:02:53,990 into our options here. 42 00:02:54,000 --> 00:02:58,990 And in this case, I'm going to turn off Maintain offset, and just leave 43 00:02:59,000 --> 00:02:59,990 everything else at the default. 44 00:03:00,000 --> 00:03:02,990 And let's go ahead and hit Add. 45 00:03:03,000 --> 00:03:07,990 And as you can see, the eye jumps a little bit to its right. 46 00:03:08,000 --> 00:03:12,990 Now the reason it's doing that is because right now we are aiming along the 47 00:03:13,000 --> 00:03:15,990 default axis, which is the X axis. 48 00:03:16,000 --> 00:03:20,990 Now we can change that in that Aim constraint option here. 49 00:03:21,000 --> 00:03:28,990 We have the Aim vector is right now 1 along X, 0 along Y and Z, but if we want 50 00:03:29,000 --> 00:03:31,990 to change it later, we can always go into the Attribute Editor. 51 00:03:32,000 --> 00:03:35,990 So I'm going to make sure my eye is selected, go into the Attribute Editor, and 52 00:03:36,000 --> 00:03:39,990 find the Eye_Rt_aimConstraint. 53 00:03:40,000 --> 00:03:42,990 Then all we have to do is find that Aim vector. 54 00:03:43,000 --> 00:03:48,990 In this case, you can see the red axis, or the X axis, is pointing towards that locator. 55 00:03:49,000 --> 00:03:53,990 We want the blue axis or the Z axis to point. 56 00:03:54,000 --> 00:03:58,990 So let's go ahead and 0 out the X axis, and notice how that already snaps. 57 00:03:59,000 --> 00:04:05,990 And then let's go ahead and make it 1 along Z. So now that I have this, you can 58 00:04:06,000 --> 00:04:09,990 see it's pointing towards that locator a lot more precisely. 59 00:04:10,000 --> 00:04:13,990 And usually, this is the way that we want to set these things up. 60 00:04:14,000 --> 00:04:17,990 So now that we know exactly how to set it up, let's go ahead and set it up 61 00:04:18,000 --> 00:04:18,990 for the second eye. 62 00:04:19,000 --> 00:04:23,990 So I'm going to click on this eye here and you can see that the blue axis again 63 00:04:24,000 --> 00:04:28,990 is the axis we want, so I'm going to select my locator, Shift+Select Eye_Lt, go 64 00:04:29,000 --> 00:04:34,990 into Constrain > Aim constraint, and in this case I don't want this to be 65 00:04:35,000 --> 00:04:42,990 constrained to X, I want it to be constrained to Y, hit Add, and there we go. 66 00:04:43,000 --> 00:04:48,990 So now, I can select my locator and the eyes will follow. 67 00:04:49,000 --> 00:04:52,990 So obviously, this guy is a little bit cross-eyed, but we can certainly do 68 00:04:53,000 --> 00:04:56,990 multiple locators if we want, and we'll get into that a little bit more 69 00:04:57,000 --> 00:04:59,990 precisely, in the later chapters. 70 00:05:00,000 --> 00:05:04,990 But as you can see, the Aim constraint can be used to point up one object at 71 00:05:05,000 --> 00:06:05,990 another, and there is a number of ways to use this in character rigging.