1 00:00:04,260 --> 00:00:05,890 ‫Hello and welcome back. 2 00:00:05,910 --> 00:00:11,130 ‫Now, we've already created our projectile class, and we're ready to start spawning these things in 3 00:00:11,130 --> 00:00:15,660 ‫the level so that we can launch them at the towers and eventually destroy them. 4 00:00:15,660 --> 00:00:19,950 ‫Now, spawning actors is going to involve the spawn actor function. 5 00:00:19,950 --> 00:00:22,470 ‫So we're going to learn how that works in this video. 6 00:00:22,470 --> 00:00:25,290 ‫Now, let's talk about spawning the projectile. 7 00:00:25,320 --> 00:00:29,130 ‫This is something we'd like to do from the C++ side of things. 8 00:00:29,130 --> 00:00:34,590 ‫We're going to call C++ functions to create new objects dynamically in the world. 9 00:00:34,590 --> 00:00:41,610 ‫Now we're spawning from the C++ side of things, but we'd like to spawn an object based on the blueprint 10 00:00:41,610 --> 00:00:43,110 ‫of our projectile class. 11 00:00:43,110 --> 00:00:50,040 ‫The reason is because we have a blueprint based on the A Projectile C++ class, which contains additional 12 00:00:50,040 --> 00:00:51,030 ‫information. 13 00:00:51,030 --> 00:00:54,270 ‫Specifically, it has that mesh property set. 14 00:00:54,270 --> 00:00:57,780 ‫We chose the mesh for our static mesh component. 15 00:00:57,780 --> 00:01:00,510 ‫So we can't just spawn the C++ version. 16 00:01:00,510 --> 00:01:04,590 ‫We have to spawn the blueprint version in order to get that mesh. 17 00:01:04,590 --> 00:01:10,650 ‫So the question is how do we spawn an object in C++, which is based on a blueprint? 18 00:01:10,650 --> 00:01:15,810 ‫Well, we're going to learn about something called PT Subclass of now this is a template. 19 00:01:15,810 --> 00:01:20,730 ‫And like many templates, the angle brackets are going to require a type. 20 00:01:20,730 --> 00:01:24,480 ‫So using PT sub class of requires a type parameter. 21 00:01:24,480 --> 00:01:29,790 ‫And this allows us to have a variable that stores something called a U class. 22 00:01:29,790 --> 00:01:36,690 ‫U class represents a class type, but it also has the ability to interact with unreal engine's reflection 23 00:01:36,690 --> 00:01:37,350 ‫system. 24 00:01:37,350 --> 00:01:43,290 ‫When I say reflection, I mean exchanging information between the C++ and the blueprint side. 25 00:01:43,320 --> 00:01:50,700 ‫PT sub class of, as the name suggests, allows us to store a variable that represents a class based 26 00:01:50,700 --> 00:01:54,870 ‫on the type we're passing in or a subclass of this chosen type. 27 00:01:54,870 --> 00:02:01,560 ‫This means we can choose a type and t sub class of can hold a u class that represents that type or any 28 00:02:01,560 --> 00:02:02,880 ‫type derived from it. 29 00:02:02,880 --> 00:02:06,360 ‫And this includes blueprints based on the type. 30 00:02:06,360 --> 00:02:09,090 ‫So let's see how this t subclass of thing works. 31 00:02:09,090 --> 00:02:09,380 ‫Okay. 32 00:02:09,390 --> 00:02:15,270 ‫So I'm back here in base pom and the reason I'm in base pod is because we want this projectile to be 33 00:02:15,270 --> 00:02:17,880 ‫on both the tank and the tower classes. 34 00:02:17,880 --> 00:02:20,910 ‫Both of those classes are going to be spawning projectiles. 35 00:02:20,910 --> 00:02:23,700 ‫So I'd like a t sub class of variable here. 36 00:02:23,700 --> 00:02:30,930 ‫So I'm going to say t sub class of and in the angle brackets we need to pass in a type. 37 00:02:30,930 --> 00:02:34,740 ‫Now we can forward declare even inside angle brackets like this. 38 00:02:34,740 --> 00:02:37,440 ‫And I'm going to make the type a projectile. 39 00:02:37,440 --> 00:02:42,690 ‫And the reason is because we created the projectile class and its type is a projectile. 40 00:02:42,690 --> 00:02:47,940 ‫So I'm going to create this variable and I'm going to call it projectile class. 41 00:02:47,940 --> 00:02:54,960 ‫Now, this is going to allow us to have a C++ variable that represents a class type, and the type can 42 00:02:54,960 --> 00:02:59,670 ‫be based on a projectile, even a blueprint class type based on this. 43 00:02:59,670 --> 00:03:02,100 ‫Now I'm going to give it a U property. 44 00:03:02,730 --> 00:03:07,620 ‫And because I'd like to be able to edit this, at least in the default blueprint, I'm going to make 45 00:03:07,620 --> 00:03:09,060 ‫this edit defaults. 46 00:03:09,060 --> 00:03:12,540 ‫Only now we can give this a category. 47 00:03:13,530 --> 00:03:16,170 ‫I'll place it in a category called combat. 48 00:03:16,200 --> 00:03:18,240 ‫Now let's go ahead and compile this. 49 00:03:18,270 --> 00:03:23,130 ‫Okay, so I'm back in the editor and I'm going to go into the blueprints folder and from there into 50 00:03:23,130 --> 00:03:24,330 ‫the Pons folder. 51 00:03:24,330 --> 00:03:29,580 ‫And I'm just going to open up BP -- tank and open full blueprint editor. 52 00:03:29,580 --> 00:03:32,910 ‫Now, if I look in the details panel, I can look for combat. 53 00:03:32,910 --> 00:03:33,840 ‫Here it is. 54 00:03:33,840 --> 00:03:36,540 ‫And here's the projectile class variable. 55 00:03:36,540 --> 00:03:40,410 ‫This is that subclass of that we called projectile class. 56 00:03:40,410 --> 00:03:44,250 ‫Now notice we can set it here and we can set it using a dropdown. 57 00:03:44,250 --> 00:03:47,910 ‫And if we click on the dropdown, we have three options. 58 00:03:47,910 --> 00:03:53,340 ‫We can set it to none, which is what it's set to by default, which basically means it's a null pointer. 59 00:03:53,340 --> 00:03:57,960 ‫Or we can set it to projectile or BP projectile. 60 00:03:57,990 --> 00:04:04,740 ‫That's what sub class of allows us to do is set this projectile class to a particular type based on 61 00:04:04,740 --> 00:04:08,880 ‫projectile, since that's the type we chose when we made the variable. 62 00:04:08,880 --> 00:04:10,140 ‫Now projectile here. 63 00:04:10,140 --> 00:04:14,520 ‫This is the C++ class called projectile in C++. 64 00:04:14,520 --> 00:04:22,260 ‫It's a projectile, but BP projectile is a blueprint based on the C++ projectile class and we can choose 65 00:04:22,260 --> 00:04:22,920 ‫this. 66 00:04:22,920 --> 00:04:27,870 ‫And now projectile class is set to the BP projectile type. 67 00:04:27,870 --> 00:04:32,610 ‫Now, this is not a component and it's not a BP projectile object. 68 00:04:32,610 --> 00:04:33,540 ‫That's not what it is. 69 00:04:33,540 --> 00:04:36,480 ‫It stores a type, more specifically a U. 70 00:04:36,480 --> 00:04:37,260 ‫Class type. 71 00:04:37,260 --> 00:04:44,730 ‫And like I said, you class has built in functionality that allows reflection to work between C++ and 72 00:04:44,730 --> 00:04:45,390 ‫blueprints. 73 00:04:45,390 --> 00:04:48,690 ‫Information can flow between C++ and blueprints. 74 00:04:48,690 --> 00:04:55,710 ‫So now we have projectile class, a PT sub class of set to the BP projectile blueprint type. 75 00:04:55,710 --> 00:04:59,790 ‫So why go through all the trouble to create a subclass of variable? 76 00:04:59,790 --> 00:05:03,750 ‫Well, we need to discuss how the spawn actor function works. 77 00:05:04,200 --> 00:05:08,400 ‫Spawn actor is a function belonging to the new world class. 78 00:05:08,400 --> 00:05:12,120 ‫So if we get a hold of the world, we can call Spawn actor. 79 00:05:12,120 --> 00:05:19,620 ‫And Spawn actor is another template function and it's designed to create new objects similar to create 80 00:05:19,620 --> 00:05:21,060 ‫default sub object. 81 00:05:21,060 --> 00:05:28,260 ‫But create default sub object is designed for creating components and we can only use it in the constructor 82 00:05:28,260 --> 00:05:35,520 ‫for a particular class spawn actor can be called at runtime while the game is running and it can create 83 00:05:35,520 --> 00:05:36,360 ‫actors. 84 00:05:36,360 --> 00:05:39,450 ‫Now it's a template, so it requires a type. 85 00:05:39,480 --> 00:05:45,780 ‫If we're wanting to spawn a projectile, then we would pass in the C++ class type here a projectile. 86 00:05:45,810 --> 00:05:52,590 ‫This is the C++ class that gets returned by the spawn actor function in C++. 87 00:05:52,620 --> 00:05:57,060 ‫Now the parentheses take a number of parameters, including a U class. 88 00:05:57,060 --> 00:06:02,190 ‫Now there are multiple overloads of this function that take different input parameters. 89 00:06:02,190 --> 00:06:07,590 ‫The most simple perhaps is the version that takes a U class, A location and a rotation. 90 00:06:07,590 --> 00:06:08,010 ‫The U. 91 00:06:08,010 --> 00:06:11,280 ‫Class is what represents the type to spawn. 92 00:06:11,310 --> 00:06:16,020 ‫This is the actual type of the object that gets spawned. 93 00:06:16,050 --> 00:06:18,300 ‫This could be a blueprint class. 94 00:06:18,330 --> 00:06:25,890 ‫The location is an F vector specifying where to spawn the object and the rotation will specify its rotation. 95 00:06:25,890 --> 00:06:28,710 ‫So an example of the syntax looks like this. 96 00:06:28,710 --> 00:06:35,580 ‫We would call spawn actor specifying the class type and then passing in that u class information along 97 00:06:35,580 --> 00:06:38,820 ‫with the location vector and rotation rotator. 98 00:06:38,820 --> 00:06:41,160 ‫So let's talk about you class for a second. 99 00:06:41,160 --> 00:06:44,970 ‫Now, as we've been saying, you class represents a class type. 100 00:06:44,970 --> 00:06:51,480 ‫When we call Spawn actor, we pass in a U class to provide the spawn actor function with information 101 00:06:51,480 --> 00:06:53,550 ‫about the object to spawn. 102 00:06:53,910 --> 00:07:01,320 ‫Yes, we passed in a type in the angle brackets, but that simply tells Spawn actor the C++ type to 103 00:07:01,320 --> 00:07:01,860 ‫create. 104 00:07:01,860 --> 00:07:04,890 ‫Whereas you class contains more information. 105 00:07:04,890 --> 00:07:11,070 ‫Let's say we created a blueprint based on a projectile and in the blueprint we set some properties such 106 00:07:11,070 --> 00:07:14,580 ‫as choosing the static mesh for the static mesh component. 107 00:07:14,580 --> 00:07:21,480 ‫Now if we were to just spawn a raw C++ class, then that static mesh will not be set on the newly spawned 108 00:07:21,480 --> 00:07:22,860 ‫projectile object. 109 00:07:22,860 --> 00:07:26,250 ‫Essentially, we'd just be spawning an invisible new actor. 110 00:07:26,430 --> 00:07:30,780 ‫However, a new class variable can represent a blueprint class. 111 00:07:30,930 --> 00:07:37,140 ‫Your class gives us the ability to have a variable on the C++ side, which represents a blueprint, 112 00:07:37,140 --> 00:07:38,730 ‫class type and spawn. 113 00:07:38,730 --> 00:07:45,900 ‫Actor can take that class as an input argument so that it can spawn a new object based on the blueprint 114 00:07:45,900 --> 00:07:48,060 ‫represented by that new class. 115 00:07:48,060 --> 00:07:54,810 ‫So a new projectile will have its static mesh property set because we're spawning a new object based 116 00:07:54,810 --> 00:07:58,560 ‫on the blueprint and not the raw C++ class. 117 00:07:58,560 --> 00:08:05,190 ‫This is why we created our subclass of because it can store a new class and we were able to set it equal 118 00:08:05,190 --> 00:08:10,050 ‫to BP projectile from our BP -- tank blueprint. 119 00:08:10,050 --> 00:08:13,020 ‫So now you know how to spawn actors. 120 00:08:13,170 --> 00:08:16,020 ‫Spawn actor belongs to the new world class. 121 00:08:16,020 --> 00:08:22,320 ‫So if you call get world and simply call Spawn actor, then you know the input requirements for this 122 00:08:22,320 --> 00:08:29,370 ‫function you pass in the C++ type in the angle brackets and the you class a location and a rotation 123 00:08:29,370 --> 00:08:30,750 ‫in the parentheses. 124 00:08:30,750 --> 00:08:35,820 ‫So for your challenge, you're going to spawn the projectile, do this in the fire function. 125 00:08:35,820 --> 00:08:41,760 ‫So call get world spawn actor and pass in a projectile in the angle brackets. 126 00:08:41,760 --> 00:08:45,390 ‫This means you're going to need to include the header file for projectile. 127 00:08:45,390 --> 00:08:52,170 ‫So don't forget that and use our new variable projectile class as the U class input parameter in the 128 00:08:52,170 --> 00:08:52,920 ‫parentheses. 129 00:08:52,920 --> 00:08:55,320 ‫Now we need a location and a rotation. 130 00:08:55,320 --> 00:09:00,480 ‫You're going to use the projectile spawn point for both location and rotation. 131 00:09:00,480 --> 00:09:02,850 ‫From the projectile spawn point component. 132 00:09:02,850 --> 00:09:09,000 ‫You can call get component location and get component rotation to access these values. 133 00:09:09,000 --> 00:09:14,040 ‫So pause the video and call spawn actor in the fire function now. 134 00:09:16,920 --> 00:09:17,310 ‫Okay. 135 00:09:17,310 --> 00:09:22,880 ‫So let's go into Base Pond CP where we have the fire function defined. 136 00:09:22,890 --> 00:09:25,230 ‫Now we have draw debug sphere here. 137 00:09:25,230 --> 00:09:27,450 ‫We're not really going to need that anymore. 138 00:09:27,450 --> 00:09:33,270 ‫So I'm going to delete this function call and instead I'm going to call Spawn actor here. 139 00:09:33,270 --> 00:09:36,750 ‫Now we already have the projectile spawn point location. 140 00:09:37,050 --> 00:09:43,770 ‫I'm going to rename this local variable to simply location and I'm going to create a new F rotator. 141 00:09:44,430 --> 00:09:45,810 ‫Called rotation. 142 00:09:45,900 --> 00:09:50,010 ‫And this I'm going to get from the projectile spawn point as well. 143 00:09:50,010 --> 00:09:56,670 ‫So it's going to be projectile spawn point get component rotation. 144 00:09:56,670 --> 00:10:01,980 ‫So now I have the location and the rotation at which to spawn the projectile. 145 00:10:02,430 --> 00:10:07,050 ‫So next I need to call spawn actor so I can call get world. 146 00:10:07,050 --> 00:10:11,910 ‫And from the world that I get from this function, I can call spawn actor. 147 00:10:12,240 --> 00:10:15,780 ‫Now this has angle brackets and parentheses, right? 148 00:10:15,780 --> 00:10:19,740 ‫So in the angle brackets, I need to use a projectile. 149 00:10:21,240 --> 00:10:25,640 ‫And since we're using a projectile, we need to include the header for that. 150 00:10:25,650 --> 00:10:32,760 ‫So up here, I'm going to remove, draw debug helpers and replace it with projectile. 151 00:10:34,740 --> 00:10:37,260 ‫So now we have that type included. 152 00:10:37,260 --> 00:10:44,070 ‫Now we need the U class and based upon H has projectile class, we can use that as the U class. 153 00:10:44,070 --> 00:10:47,050 ‫So we're going to pass in projectile class. 154 00:10:47,070 --> 00:10:54,750 ‫Now, finally, we can pass in location and rotation and this will satisfy the spawn actor function. 155 00:10:54,750 --> 00:11:00,420 ‫So let's go ahead and compile this and we're back here in the editor and we can test play. 156 00:11:00,420 --> 00:11:04,080 ‫So I'm going to go ahead and click and check that out. 157 00:11:04,080 --> 00:11:06,750 ‫We have spawned a new projectile. 158 00:11:06,750 --> 00:11:13,680 ‫We're spawning the projectile at the tip of our barrel and they kind of just hover there in the air, 159 00:11:13,680 --> 00:11:15,660 ‫which doesn't really look right. 160 00:11:15,660 --> 00:11:16,430 ‫But that's okay. 161 00:11:16,440 --> 00:11:17,700 ‫This is step one. 162 00:11:17,700 --> 00:11:23,580 ‫We first have to spawn the projectile, getting it to act like a projectile as the next step. 163 00:11:23,580 --> 00:11:27,120 ‫So in summary, we are now spawning projectiles. 164 00:11:27,150 --> 00:11:29,060 ‫This is a great milestone. 165 00:11:29,070 --> 00:11:32,250 ‫However, they're not quite projectiles yet. 166 00:11:32,280 --> 00:11:36,060 ‫They just hover there and projectiles are supposed to fly through the air. 167 00:11:36,210 --> 00:11:41,490 ‫So in the next video, we're going to talk about how to make our projectiles actually fly through the 168 00:11:41,490 --> 00:11:43,800 ‫air so they're acting like projectiles. 169 00:11:43,830 --> 00:11:44,700 ‫I'll see you soon.