1 00:00:04,130 --> 00:00:04,610 ‫Hey. 2 00:00:04,610 --> 00:00:05,450 ‫Welcome back. 3 00:00:05,480 --> 00:00:09,080 ‫Now, we've already created a base -- C++ class. 4 00:00:09,200 --> 00:00:16,310 ‫In this video, we're going to derive from that class to create a new child class based on base --. 5 00:00:16,340 --> 00:00:19,310 ‫So let's discuss why we'd want to do such a thing. 6 00:00:19,580 --> 00:00:26,300 ‫So we have this base -- class and we know that we're going to have two different classes that derive 7 00:00:26,300 --> 00:00:27,080 ‫from base --. 8 00:00:27,080 --> 00:00:30,020 ‫We're going to have our tank and we're going to have the tower. 9 00:00:30,050 --> 00:00:34,760 ‫Now, the base -- contains meshes, a capsule as well as a spawn point. 10 00:00:34,760 --> 00:00:38,210 ‫And these are things that the Tank and tower can both inherit. 11 00:00:38,360 --> 00:00:44,480 ‫But the tank and tower are also going to have some functionality that differs from each other. 12 00:00:44,480 --> 00:00:50,060 ‫For one, our tank is going to move around in the world and it's also going to be controlled by the 13 00:00:50,060 --> 00:00:50,720 ‫player. 14 00:00:50,720 --> 00:00:55,220 ‫So it'll need to be configured to take input from the keyboard and mouse. 15 00:00:55,220 --> 00:00:57,950 ‫The tower, on the other hand, is just going to sit there. 16 00:00:57,980 --> 00:01:03,860 ‫It has no need for any input from the player as its actions will all be controlled by code. 17 00:01:03,860 --> 00:01:10,010 ‫So because the tank and tower will behave differently, we're going to make use of inheritance to create 18 00:01:10,010 --> 00:01:16,730 ‫child classes of base -- so we can inherit what they have in common and then add to each class those 19 00:01:16,730 --> 00:01:18,290 ‫features that will be different. 20 00:01:18,290 --> 00:01:23,960 ‫So we're back here in the editor and I'm going to go into our C++ classes, Tune Tank's folder where 21 00:01:23,960 --> 00:01:29,240 ‫we have our base -- class and this will be the class that we're deriving from. 22 00:01:29,240 --> 00:01:35,480 ‫Now we can right click here and select create C++ class derived from base --. 23 00:01:35,480 --> 00:01:41,690 ‫So let's choose that and I'm going to allow it to stick this class in the same source slash tune tanks 24 00:01:41,690 --> 00:01:43,550 ‫folder as base --. 25 00:01:43,610 --> 00:01:47,360 ‫And for the name of this, I'm going to call it tank. 26 00:01:47,360 --> 00:01:54,560 ‫So our tank class will be the class for our actual tank -- that we're controlling and moving around 27 00:01:54,560 --> 00:01:55,400 ‫in the world. 28 00:01:55,430 --> 00:01:57,410 ‫So let's click create class. 29 00:01:57,560 --> 00:02:06,470 ‫Okay, so we've compiled and vs code has opened up with our new tank file and we also have Tank CP. 30 00:02:06,500 --> 00:02:08,210 ‫Now these are pretty bare. 31 00:02:08,210 --> 00:02:14,570 ‫There's really nothing here, but even though we can't see them, we have inherited some things from 32 00:02:14,570 --> 00:02:15,950 ‫the base -- class. 33 00:02:15,950 --> 00:02:19,580 ‫We do have those components that we've added to base --. 34 00:02:19,580 --> 00:02:23,810 ‫Even though those are private variables, they still exist in this class. 35 00:02:23,810 --> 00:02:29,030 ‫So now that we've created our tank class, let's talk about a couple of things. 36 00:02:29,030 --> 00:02:31,880 ‫The tank will need that the turret will not. 37 00:02:31,880 --> 00:02:37,490 ‫Well, since we're going to be controlling the tank, we're going to need a way to focus on the tank 38 00:02:37,490 --> 00:02:39,530 ‫as it's rolling around throughout the level. 39 00:02:39,950 --> 00:02:43,880 ‫Now, in this picture, this here is a camera component. 40 00:02:43,880 --> 00:02:47,030 ‫It's C++ class is you camera component. 41 00:02:47,180 --> 00:02:55,100 ‫And this red line here is called a spring arm component and its C++ class is you spring arm component. 42 00:02:55,100 --> 00:03:01,370 ‫Adding these components to a -- allows us to view the -- from the point of view of the camera. 43 00:03:01,370 --> 00:03:07,790 ‫And if the camera and its spring arm are attached to the -- in some way, they will follow the -- 44 00:03:07,790 --> 00:03:08,930 ‫around in the world. 45 00:03:08,930 --> 00:03:14,540 ‫Now, back here in the editor, if we go back to our --'s folder and open BP -- tank, we can click 46 00:03:14,540 --> 00:03:16,730 ‫the viewport so we can see everything. 47 00:03:16,730 --> 00:03:22,100 ‫And then we can select the capsule comp and click add and select spring arm. 48 00:03:22,100 --> 00:03:24,080 ‫This is a spring arm component. 49 00:03:24,080 --> 00:03:25,610 ‫It looks like a red line. 50 00:03:25,730 --> 00:03:31,490 ‫Now with our spring arm component selected, we can add another component and choose camera. 51 00:03:31,490 --> 00:03:37,400 ‫Now, once we've added the camera attached to the spring arm, we now have a way to see from the point 52 00:03:37,400 --> 00:03:41,230 ‫of view of the camera once we actually start controlling the --. 53 00:03:41,240 --> 00:03:43,040 ‫Now the spring arm is pretty useful. 54 00:03:43,040 --> 00:03:49,250 ‫It has this target arm length and if you adjust it, you'll see that the camera adjusts along with the 55 00:03:49,250 --> 00:03:49,940 ‫spring arm. 56 00:03:49,940 --> 00:03:54,470 ‫So this is a way to control how far away the camera is from the --. 57 00:03:54,470 --> 00:04:00,170 ‫So these are definitely things that we want on our -- class, but we're going to add them from the 58 00:04:00,170 --> 00:04:04,460 ‫C++ side rather than just adding them here in the blueprint. 59 00:04:04,460 --> 00:04:05,750 ‫So I'm going to delete those. 60 00:04:05,750 --> 00:04:10,130 ‫So for your challenge, I'd like you to add some things to the tank class. 61 00:04:10,130 --> 00:04:15,890 ‫For one, we need a spring arm component and a camera component, so create these variables and make 62 00:04:15,890 --> 00:04:16,790 ‫them pointers. 63 00:04:16,790 --> 00:04:21,920 ‫Go ahead and make a public and a private section and put these variables in the private section. 64 00:04:21,920 --> 00:04:27,590 ‫Now we'll need these to be U properties, so give them you property macros and fill in those macros 65 00:04:27,590 --> 00:04:31,610 ‫with the appropriate specifiers based on what you've learned in the previous lectures. 66 00:04:31,640 --> 00:04:36,920 ‫Now, once you've created these variables, create a constructor and put this in the public section 67 00:04:36,920 --> 00:04:44,120 ‫and define it in the CP file, and then inside the constructor construct our camera and spring arm components 68 00:04:44,120 --> 00:04:46,340 ‫using create default sub object. 69 00:04:46,340 --> 00:04:50,750 ‫Make sure to use setup attachment to attach these components to something. 70 00:04:50,750 --> 00:04:54,380 ‫We'd like our spring arm component attached to the root component. 71 00:04:54,380 --> 00:05:00,500 ‫So use root component and set setup attachment and for the camera, attach it to the spring arm. 72 00:05:00,500 --> 00:05:02,870 ‫You can refer back to the base -- class. 73 00:05:03,020 --> 00:05:05,950 ‫A Remind yourself what the code looks like to do these things. 74 00:05:05,960 --> 00:05:09,710 ‫Go ahead and pause the video and add these things to the tank class. 75 00:05:12,580 --> 00:05:13,180 ‫All right. 76 00:05:13,180 --> 00:05:14,380 ‫So we're here in Tank. 77 00:05:15,250 --> 00:05:16,540 ‫Now, first things first. 78 00:05:16,540 --> 00:05:20,110 ‫I'd like to have a public section and a private section. 79 00:05:20,350 --> 00:05:24,840 ‫So the private section will be where we add these two new components. 80 00:05:24,850 --> 00:05:31,810 ‫We're going to want a U spring arm component, which will be a pointer, and we can call this spring 81 00:05:31,810 --> 00:05:32,290 ‫arm. 82 00:05:32,290 --> 00:05:37,760 ‫And we'll also need a new camera component and we'll call this camera. 83 00:05:37,780 --> 00:05:38,260 ‫That's okay. 84 00:05:38,260 --> 00:05:39,970 ‫If your names are slightly different. 85 00:05:40,090 --> 00:05:45,070 ‫Now, right off the bat, I'm seeing the IntelliSense errors here, which means I'm going to need to 86 00:05:45,070 --> 00:05:46,420 ‫forward declare these. 87 00:05:46,420 --> 00:05:51,280 ‫So I'm going to use class with spring arm and class with camera. 88 00:05:51,280 --> 00:05:53,150 ‫And now these are forward declared. 89 00:05:53,170 --> 00:05:55,240 ‫Now we need our new properties. 90 00:05:55,240 --> 00:05:57,460 ‫So let's add the new property macros. 91 00:05:57,970 --> 00:06:02,930 ‫And inside the property macro we're going to want to have some specifiers. 92 00:06:02,950 --> 00:06:09,550 ‫These will be visible anywhere as we saw that the components need to have visible anywhere for us to 93 00:06:09,550 --> 00:06:13,010 ‫be able to adjust their parameters in the details panel. 94 00:06:13,030 --> 00:06:18,550 ‫Now, I'm not seeing any immediate need for exposure to the event graph, so I don't think we need blueprint 95 00:06:18,550 --> 00:06:20,600 ‫read, write or blueprint read only. 96 00:06:20,620 --> 00:06:21,160 ‫That's okay. 97 00:06:21,160 --> 00:06:23,770 ‫If you added them, I'm going to leave them out now. 98 00:06:23,770 --> 00:06:25,630 ‫I'm going to give these a category. 99 00:06:26,410 --> 00:06:32,230 ‫And since these are components, I'm going to just stick them in our components category along with 100 00:06:32,230 --> 00:06:33,330 ‫our other components. 101 00:06:33,340 --> 00:06:38,470 ‫Now I'm not exposing these to the event graph, so I don't need our meta allow private access specified 102 00:06:38,500 --> 00:06:38,940 ‫here. 103 00:06:38,950 --> 00:06:45,640 ‫So this is enough for spring arm and I'd like to give the camera component the same you property. 104 00:06:46,180 --> 00:06:47,590 ‫So I'm copying it over. 105 00:06:47,590 --> 00:06:49,270 ‫So now we have our components. 106 00:06:49,420 --> 00:06:54,700 ‫The next thing to do is to construct them in the constructor, which means we need a constructor. 107 00:06:54,700 --> 00:07:02,650 ‫Now the constructor will be the same name as the class, so it's a tank and we need to define this constructor 108 00:07:02,650 --> 00:07:03,910 ‫in the CP file. 109 00:07:03,910 --> 00:07:08,710 ‫So let's go to Tank CP and create a tank. 110 00:07:09,520 --> 00:07:16,180 ‫So there's our function body and the tank constructor must be prefixed with our class name and the scope 111 00:07:16,180 --> 00:07:17,710 ‫resolution operator. 112 00:07:17,710 --> 00:07:19,360 ‫That's these double colons here. 113 00:07:19,360 --> 00:07:24,850 ‫That way we're not just creating a new function, but defining our constructor for this class. 114 00:07:24,850 --> 00:07:27,130 ‫Now we'd like to construct these components. 115 00:07:27,130 --> 00:07:29,530 ‫So let's start with the spring arm. 116 00:07:29,860 --> 00:07:39,160 ‫So we're going to say spring arm equals create default sub object and this will be a u spring arm component. 117 00:07:41,260 --> 00:07:45,310 ‫And for the text, I'll simply call this spring arm. 118 00:07:46,270 --> 00:07:54,490 ‫And for the attachment, we're going to set spring arm, set up attachment, passing in root component. 119 00:07:55,920 --> 00:07:56,220 ‫Now. 120 00:07:56,220 --> 00:07:57,240 ‫I was waiting for it. 121 00:07:57,240 --> 00:07:58,050 ‫There it is. 122 00:07:58,050 --> 00:08:03,920 ‫The IntelliSense error saying pointer to incomplete class type use spring arm component. 123 00:08:03,930 --> 00:08:10,320 ‫That's because we need to include the header file since we're creating and using a spring arm component. 124 00:08:10,320 --> 00:08:16,020 ‫So here's my unreal engine documentation and if I scroll down, there's my include. 125 00:08:16,020 --> 00:08:21,820 ‫So I'm going to copy that and paste it right here at the top, just under tank edge. 126 00:08:21,900 --> 00:08:26,520 ‫Now, just a side note in general, you're going to keep your class header file included at the top 127 00:08:26,520 --> 00:08:29,370 ‫and includes for your components underneath that. 128 00:08:29,370 --> 00:08:30,750 ‫So we have our spring arm. 129 00:08:30,750 --> 00:08:32,790 ‫It's time to construct the camera. 130 00:08:32,790 --> 00:08:39,300 ‫So we're going to say camera create default sub object, you camera component. 131 00:08:40,050 --> 00:08:45,240 ‫And in the text macro, I'm going to call this simply camera. 132 00:08:45,240 --> 00:08:51,120 ‫And for the camera I'm going to call setup attachment passing in spring arm. 133 00:08:51,390 --> 00:08:54,240 ‫And of course I need the camera header file. 134 00:08:54,240 --> 00:08:59,820 ‫So here's the unreal engine documentation and here where it says search documentation, I'm going to 135 00:08:59,820 --> 00:09:05,490 ‫type you camera component and here I see you camera component. 136 00:09:05,490 --> 00:09:06,600 ‫I'll select that. 137 00:09:06,600 --> 00:09:09,450 ‫And here's the documentation for camera component. 138 00:09:09,450 --> 00:09:14,100 ‫So I'll copy it to include paste it right here at the top of our file. 139 00:09:14,100 --> 00:09:15,930 ‫And now we should be good. 140 00:09:15,960 --> 00:09:18,630 ‫Okay, so let's go ahead and compile this. 141 00:09:18,810 --> 00:09:19,230 ‫Okay. 142 00:09:19,230 --> 00:09:21,180 ‫So I have a successful compile. 143 00:09:21,210 --> 00:09:24,210 ‫Let's head back in the editor and here on -- Tank. 144 00:09:24,240 --> 00:09:30,690 ‫Of course, we don't see anything because -- tank is derived from base -- and the components we 145 00:09:30,690 --> 00:09:33,510 ‫just added, we added to the tank class. 146 00:09:33,510 --> 00:09:39,720 ‫So BP -- tank is not going to get those because it's not derived from the tank class. 147 00:09:39,720 --> 00:09:44,910 ‫Now we could go and create a new blueprint based on the tank class, but then we'd have to set up these 148 00:09:44,910 --> 00:09:46,710 ‫components all over again. 149 00:09:46,710 --> 00:09:50,190 ‫And I don't really feel like going through all that work a second time. 150 00:09:50,190 --> 00:09:55,080 ‫There's an easier way we can repair this blueprint to the tank class. 151 00:09:55,080 --> 00:10:01,530 ‫We do that by going up to class settings and in the details panel with class settings selected, we 152 00:10:01,530 --> 00:10:04,980 ‫see class options and there's this parent class. 153 00:10:04,980 --> 00:10:10,800 ‫The dropdown shows that it's set to base upon, but if we click on it, we can search for tank and choose 154 00:10:10,800 --> 00:10:13,200 ‫tank as the base class. 155 00:10:13,200 --> 00:10:17,220 ‫And now this blueprint is derived from the tank class. 156 00:10:17,220 --> 00:10:23,070 ‫So we see that all of those properties we set with our components such as the mesh and the capsule size, 157 00:10:23,070 --> 00:10:24,630 ‫they're all still there. 158 00:10:24,660 --> 00:10:27,090 ‫Only now we see a camera. 159 00:10:27,390 --> 00:10:29,730 ‫In fact, we have a spring arm and a camera. 160 00:10:29,730 --> 00:10:33,720 ‫And if we select the spring arm now, we can see that red line. 161 00:10:33,720 --> 00:10:34,710 ‫So this is great. 162 00:10:34,710 --> 00:10:38,880 ‫So I could take this spring arm component and change its target arm length. 163 00:10:38,880 --> 00:10:46,650 ‫If I like, I could set it to something like 600 and I can even change its rotation so that it's angling 164 00:10:46,650 --> 00:10:52,770 ‫the camera down at the tank by selecting rotation mode and rotating it up a bit. 165 00:10:52,770 --> 00:10:58,500 ‫Like So now I'd like to point out that you shouldn't change the camera's location. 166 00:10:58,530 --> 00:11:03,990 ‫It might be tempting to select the camera and move it around in the world so that you position it and 167 00:11:03,990 --> 00:11:05,190 ‫angle it just right. 168 00:11:05,190 --> 00:11:07,350 ‫But this is not the correct way to do it. 169 00:11:07,350 --> 00:11:13,410 ‫The correct way is to set the rotation and target arm length of the spring arm component. 170 00:11:13,410 --> 00:11:17,790 ‫And the reason is you want that camera attached to the end of the spring arm. 171 00:11:17,790 --> 00:11:23,460 ‫The spring arm has lots of different built in features such as shrinking in when the camera hits up 172 00:11:23,460 --> 00:11:29,430 ‫against a wall to avoid obstacles, blocking the view to the pond and other things like that. 173 00:11:29,430 --> 00:11:35,070 ‫So you're going to want that camera attached to the end of the spring arm and then adjust the spring 174 00:11:35,070 --> 00:11:39,990 ‫arm rather than adjusting the camera's position and rotation. 175 00:11:40,110 --> 00:11:47,070 ‫So in this video we created the tank class and we derived from base pond to inherit those qualities 176 00:11:47,070 --> 00:11:48,960 ‫from the base pond class. 177 00:11:49,140 --> 00:11:56,100 ‫We added a spring arm component and a camera component and exposed those to the editor using visible 178 00:11:56,100 --> 00:11:58,500 ‫only and put them in their own category. 179 00:11:58,500 --> 00:12:03,900 ‫So we're getting closer to the finished product step by step, and we'll continue developing this tank 180 00:12:03,900 --> 00:12:05,130 ‫in the next lecture. 181 00:12:05,460 --> 00:12:06,510 ‫I'll see you soon.