WEBVTT 00:06.870 --> 00:07.950 Welcome back. 00:07.950 --> 00:12.600 Now in this video we're going to implement our highlighting behavior. 00:12.630 --> 00:18.840 Now we've already discussed how the player controller has the ability to get whatever actor is underneath 00:18.840 --> 00:19.740 the cursor. 00:19.740 --> 00:23.220 At any given point in time we're going to do this. 00:23.220 --> 00:30.090 And this is something I'd like to do every frame, as it's not a very expensive operation to do, and 00:30.090 --> 00:35.970 we need that sort of responsiveness when hovering the mouse cursor over various different actors. 00:36.120 --> 00:42.360 So in our player controller dot h file, we're going to override a tick function. 00:42.360 --> 00:46.920 We're going to say virtualvoid and we're going to override player tick. 00:47.010 --> 00:49.650 So let's make a definition for this. 00:49.650 --> 00:56.550 And in player tick we're going to perform our trace and handle the highlighting of any actors we hit 00:56.550 --> 00:58.860 that implement the enemy interface. 00:58.860 --> 01:02.070 So I'd like to make a function to call here in player tick. 01:02.070 --> 01:06.210 And this function is going to trace under the cursor. 01:06.210 --> 01:08.760 So I'm going to call this function cursor trace. 01:08.760 --> 01:10.800 And I'm going to make it private. 01:10.800 --> 01:18.360 So down at the bottom we'll make a void cursor trace I'll go ahead and implement this. 01:18.360 --> 01:23.340 And I don't want this inlined I'm going to move it. 01:24.450 --> 01:28.080 Back out into the player controller dot cpp file. 01:28.080 --> 01:32.400 And the first thing I'm going to do is call cursor trace here in player tic. 01:32.910 --> 01:38.430 Now cursor trace is going to involve getting the hit result under the cursor. 01:38.430 --> 01:43.710 That's something that the player controller class inherently has the ability to do. 01:43.710 --> 01:47.700 So to do that we make a hit result f hit result. 01:48.930 --> 01:56.160 We'll call this cursor hit, and the player controller function that we're interested in is get hit 01:56.160 --> 01:57.870 result under cursor. 01:57.870 --> 02:02.640 And this takes a trace channel we can trace against the visibility channel. 02:02.640 --> 02:11.460 So that's going to be a collision channel visibility or simply EQ visibility trace complex is going 02:11.460 --> 02:12.210 to be false. 02:12.210 --> 02:15.630 We want to trace against simple collision only. 02:15.630 --> 02:18.030 And the hit result is our cursor hit. 02:18.510 --> 02:22.410 So after calling this we now have a hit result. 02:22.410 --> 02:29.010 And we can check if we got a blocking hit by checking if cursor hit dot blocking hit. 02:30.270 --> 02:38.490 And if we don't want too much logic nested, we can simply say if not, cursor hit dot blocking, hit 02:38.490 --> 02:42.540 return and the next lines of code won't be indented. 02:42.540 --> 02:46.080 Okay, so what are we going to do with this hit result? 02:46.080 --> 02:50.130 Well, we want to see if it implements the enemy interface. 02:50.130 --> 02:52.410 And we can simply perform a cast here. 02:52.410 --> 02:58.080 So we can say cast and we can cast to I enemy interface. 02:58.200 --> 03:02.370 We're casting cursor hit dot get actor. 03:02.370 --> 03:04.500 That's the actor that was hit. 03:04.950 --> 03:11.010 If this cast succeeds, then the actor we hit implements the I enemy interface. 03:11.370 --> 03:16.140 Now, if the actor is not an I enemy interface, it doesn't implement it. 03:16.140 --> 03:20.550 Then this cast returns a null pointer and we can use that information. 03:20.550 --> 03:23.460 What I'd like to do is have two pointers. 03:23.460 --> 03:31.320 One for the actor that we're hovering over this frame, and one for the actor we hovered over last frame. 03:31.320 --> 03:35.880 Now from frame to frame, they could be the same or they could be different. 03:35.880 --> 03:42.000 And what we do depends on whether they're the same or different, whether they're null or not null. 03:42.000 --> 03:43.560 So I'm going to make two pointers. 03:43.560 --> 03:49.710 And rather than pointers to actors, I'm going to make pointers to the I enemy interface. 03:49.710 --> 03:57.210 So I'm going to forward declare that up here at the top I'm going to say class I enemy interface. 03:58.260 --> 04:07.050 Now I'm going to have an AI enemy interface called Last Actor and an AI enemy interface called this 04:07.050 --> 04:07.560 actor. 04:07.560 --> 04:08.880 Both pointers. 04:09.330 --> 04:11.760 Hey there Steven from the future here. 04:11.760 --> 04:14.610 Coming back with an important message for you. 04:14.610 --> 04:22.080 In the original version of this course, we used a raw pointer for I enemy interface for a member variable, 04:22.080 --> 04:25.890 and this is actually not the correct way to do it. 04:25.890 --> 04:34.080 The correct way to hold a member variable to an interface is by using a special wrapper designed to 04:34.080 --> 04:35.490 hold interfaces. 04:35.490 --> 04:37.650 So it looks like this. 04:37.650 --> 04:41.070 The wrapper is T script interface. 04:41.160 --> 04:46.980 It's a template wrapper, so we have to put the interface type within pointy brackets. 04:46.980 --> 04:49.740 That's going to be I enemy interface. 04:50.460 --> 04:52.200 No asterisk needed. 04:52.200 --> 04:59.220 So our last actor is going to be stored using this interface wrapper T script interface. 04:59.220 --> 05:01.290 And the same goes for this actor. 05:01.290 --> 05:04.170 It's going to be a T script interface as well. 05:04.170 --> 05:10.110 So even though the lectures have raw pointers for I enemy interface, don't do that. 05:10.110 --> 05:13.560 Do it the right way by using t script interface. 05:13.590 --> 05:21.270 Now this does change the way we use these pointers slightly, as we'll see in just a moment. 05:22.460 --> 05:30.380 And back here in Cursor Trace, I'm first going to set last actor equal to this actor each frame. 05:30.830 --> 05:35.600 And then this actor will be set to the result of this cast. 05:35.600 --> 05:36.800 I'm going to move it here. 05:37.510 --> 05:43.990 Steven from the future here again, letting you know that this is where we differ from the video. 05:43.990 --> 05:49.720 Once again, because we're now using a script interface, this cast is unnecessary. 05:49.720 --> 05:51.400 We don't have to cast. 05:51.400 --> 05:57.130 All we have to do is set this actor using cursor hit dot, get actor. 05:57.220 --> 06:04.210 So don't perform the cast, use script interface and set this actor directly. 06:04.210 --> 06:06.610 This script interface is pretty nice, right? 06:06.610 --> 06:11.920 So the cast may fail, which means this actor would be currently a null pointer. 06:11.920 --> 06:17.800 And last actor will store what this actor was before we updated it. 06:17.800 --> 06:22.990 In other words, what it was last frame so we can check the values of these. 06:23.410 --> 06:23.950 Now. 06:23.950 --> 06:29.620 There are several scenarios that we need to cover, and I'd like to write these out with some pseudocode 06:29.620 --> 06:30.550 comments. 06:30.550 --> 06:33.760 So I'm going to make a multi-line comment actually. 06:34.030 --> 06:38.710 And this comment will say line trace from cursor. 06:40.380 --> 06:43.470 There are several scenarios. 06:44.510 --> 06:56.030 So one scenario we'll call it a is that last actor is null and this actor is null. 06:56.300 --> 07:00.830 So this is probably one of the simplest scenarios, right. 07:00.830 --> 07:04.190 Whatever our cursor hit got last frame. 07:04.190 --> 07:06.140 It was not an enemy interface. 07:06.140 --> 07:10.490 It was probably a wall or a floor or something like that. 07:10.490 --> 07:12.140 And the same for this frame. 07:12.140 --> 07:17.120 We're not hitting an enemy interface, so we don't need to try to call the interface function. 07:17.120 --> 07:20.480 In fact, all we have to do in this case is do nothing. 07:20.810 --> 07:24.350 So that's the easiest scenario. 07:24.350 --> 07:32.780 Now another scenario is that last actor is null, but this actor is valid. 07:32.780 --> 07:37.400 In other words, this actor is an enemy interface. 07:37.400 --> 07:39.680 So we do something in that case right? 07:39.680 --> 07:40.490 What do we do? 07:40.490 --> 07:42.740 Well last actor is null. 07:42.740 --> 07:45.440 So we can't really call any functions on that. 07:45.440 --> 07:52.640 But this actor is valid, which means that we're hovering over this actor for the first time. 07:52.640 --> 07:57.830 We weren't hovering over this actor last frame that we know because last actor is null. 07:57.830 --> 08:04.280 So if this is the first frame we're hovering over this actor we can call highlight on this actor. 08:04.280 --> 08:08.240 So we're going to say highlight this actor. 08:09.440 --> 08:11.510 Now I'm going to remove the periods there. 08:11.540 --> 08:12.230 All right. 08:12.230 --> 08:14.090 So that's that scenario. 08:14.930 --> 08:23.480 Now another scenario is that last actor is valid and this actor is null. 08:23.660 --> 08:25.130 What does that mean. 08:25.250 --> 08:31.730 Well if that's the case then we hovered over an enemy interface last frame. 08:31.730 --> 08:34.400 And this frame we're no longer hovering over it. 08:34.400 --> 08:38.030 That's the case where we want to unhighlight that actor. 08:38.030 --> 08:42.500 So we're going to say in this case, unhighlight last actor. 08:43.270 --> 08:48.760 We were hovering over it before, and this frame were now no longer hovering over it, so unhighlight 08:48.760 --> 08:49.270 it. 08:49.300 --> 08:52.120 Okay, so that's three different scenarios. 08:52.120 --> 08:53.980 Can we think of any others? 08:54.580 --> 08:57.610 Well, what about if both actors are valid. 08:59.770 --> 09:04.960 But last actor is not equal to this actor. 09:05.980 --> 09:07.330 So what does that mean. 09:07.330 --> 09:10.240 So last actor is not null. 09:10.240 --> 09:11.890 This actor is not null. 09:11.890 --> 09:14.230 But they're different actors. 09:14.230 --> 09:19.930 That means we were hovering over one enemy, and then suddenly we started hovering over a different 09:19.930 --> 09:20.500 enemy. 09:20.500 --> 09:24.520 Which means that last actor should no longer be highlighted. 09:24.520 --> 09:26.620 But this frames actor. 09:26.620 --> 09:30.160 This actor was not being highlighted last frame. 09:30.160 --> 09:32.620 We're switching from one enemy to another. 09:32.620 --> 09:40.720 So what we need to do here is Unhighlight last actor and highlight this actor. 09:41.980 --> 09:42.280 Right? 09:42.280 --> 09:46.240 So that's one of those weird edge cases that can definitely happen. 09:46.240 --> 09:49.210 Now what's the one other scenario we haven't covered? 09:49.210 --> 09:55.030 Well, what if both actors are valid and are the same actor? 09:55.030 --> 09:57.970 In other words, last actor is this actor. 09:57.970 --> 10:00.670 Well, that just means we're hovering over an enemy. 10:00.670 --> 10:04.690 And we were hovering over that same enemy last frame. 10:04.690 --> 10:10.390 And that means we've already highlighted it because we were hovering over it last frame. 10:10.390 --> 10:16.060 We know that the first time we hovered over it, we called Highlight Actor, so we don't need to highlight 10:16.060 --> 10:16.360 it. 10:16.360 --> 10:19.780 We're still hovering over it, so we don't need to unhighlight it. 10:19.780 --> 10:22.210 So in this case we do nothing. 10:22.780 --> 10:26.440 So these are the five scenarios that we have to handle. 10:27.100 --> 10:32.890 And we can check the validity of last actor and this actor to know which of these functions we should 10:32.890 --> 10:35.290 call or whether we should do nothing. 10:35.290 --> 10:42.070 So the first thing I'm going to do is I'm going to check if last actor and I'm going to explicitly say 10:42.070 --> 10:44.050 last actor equals null pointer. 10:45.370 --> 10:47.590 Equals null pointer is optional. 10:47.590 --> 10:51.550 I'm explicitly stating it as a matter of style here. 10:51.550 --> 10:56.680 Now, if last actor is null, then we know that A is a possibility, right? 10:56.680 --> 10:59.680 Last actor is null and this actor is null. 10:59.680 --> 11:03.220 That's case A, and in that case we do nothing. 11:03.220 --> 11:07.570 But if last actor is null and this actor is valid, well that's case B. 11:07.570 --> 11:14.440 So what we can do inside this if check is check if this actor is valid. 11:14.440 --> 11:17.440 In other words this actor is not null pointer. 11:18.440 --> 11:20.390 So last actor is null. 11:20.390 --> 11:22.070 This actor is valid. 11:22.070 --> 11:23.450 This is case B. 11:23.600 --> 11:26.360 So we're going to say case B. 11:26.360 --> 11:31.070 And for case B we know that we have to call highlight on this actor. 11:31.070 --> 11:35.540 So we're going to call this actor highlight actor. 11:35.630 --> 11:41.210 Now if we have an else case here that would mean that this actor is null. 11:41.210 --> 11:44.750 In other words we'll say both are null. 11:45.050 --> 11:46.490 Do nothing. 11:47.510 --> 11:52.850 And this is case A so we can have case A first let's make this neat. 11:52.850 --> 11:55.880 We'll say case A both are null. 11:55.880 --> 11:56.480 Do nothing. 11:56.480 --> 12:00.530 In other words this else statement is completely unnecessary. 12:00.530 --> 12:06.080 But I'm keeping it here just so we can show that we're checking each of these cases. 12:06.080 --> 12:08.450 So that takes care of A and B. 12:08.780 --> 12:13.970 Now if last actor is not a null pointer well we have an else case here then. 12:14.510 --> 12:19.490 So I'll put a little comment here and say last actor is valid. 12:19.490 --> 12:25.280 Now if last actor is valid but this actor is null, that's case C. 12:25.490 --> 12:33.950 So we'll have an if in here that says if this actor is a null pointer then we can say this is case C 12:34.670 --> 12:38.120 and what do we do in case C we unhighlight last actor. 12:38.120 --> 12:42.920 So we're going to say last actor Unhighlight actor. 12:43.400 --> 12:45.620 So that takes care of case C. 12:45.650 --> 12:50.000 Now if this actor is not null, in other words we'll have an else here. 12:50.000 --> 12:54.320 Then that means last actor is valid and this actor is valid. 12:54.320 --> 12:58.370 In other words, we'll have a comment that says both actors are valid. 12:58.370 --> 13:02.000 Now, if both actors are valid, we have two possibilities. 13:02.000 --> 13:05.270 They are the same actor or they're not the same actor. 13:05.270 --> 13:12.800 So if both actors are valid, we'll have another check that says if last actor is not equal to this 13:12.800 --> 13:13.550 actor. 13:15.630 --> 13:18.390 So they're both valid but they're not equal. 13:18.390 --> 13:19.530 That's case D. 13:19.680 --> 13:23.460 So we have to unhighlight last actor and highlight this actor. 13:23.460 --> 13:25.350 So we're going to say case D. 13:26.940 --> 13:30.000 Case D is Unhighlight last actor. 13:30.000 --> 13:36.150 So we're going to say last actor Unhighlight actor and highlight this actor. 13:36.150 --> 13:40.110 So this actor highlight actor. 13:40.380 --> 13:45.300 And if they're not equal to each other then they're both valid and they're the same. 13:45.300 --> 13:49.350 In other words we'll have an else here that says case E, right. 13:49.350 --> 13:52.770 Both actors are valid and they are the same actor. 13:52.770 --> 13:55.620 So we'll say case E do nothing. 13:57.000 --> 13:57.570 Okay. 13:57.570 --> 13:58.950 So this handles all the cases. 13:58.950 --> 14:04.290 And of course, you know, the code could be more compact if we wanted to. 14:04.290 --> 14:08.430 We have some unnecessary else statements with just comments in them. 14:08.430 --> 14:14.070 That's just to make sure that it's understood what we're doing here. 14:14.070 --> 14:17.430 When on a fresh pair of eyes looks at this function. 14:17.430 --> 14:22.920 So if you want, you can remove all these comments and have a nice clean little algorithm. 14:22.920 --> 14:26.040 I'm going to keep all the comments here because it's more descriptive. 14:26.040 --> 14:30.210 And so now we have this cursor trace going on every frame. 14:30.210 --> 14:34.680 And the only thing left to do is test out this system to see if it works. 14:34.680 --> 14:36.510 And that's going to be your quest. 14:36.720 --> 14:40.800 What I'd like you to do is show some kind of visual feedback. 14:40.800 --> 14:48.180 Whenever we call highlight actor and unhighlight actor, draw a debug sphere, or show some kind of 14:48.180 --> 14:53.160 message in the output log or something so that we know these functions are being called. 14:53.160 --> 15:00.330 You may wish to create, say, a boolean and expose that to blueprint and check that in the blueprint 15:00.330 --> 15:03.810 and draw a debug sphere, say in the tick function. 15:03.810 --> 15:10.440 If the boolean is true, decide how you'd like to implement it and test out our highlighting system 15:10.440 --> 15:11.370 now. 15:14.370 --> 15:22.020 Okay, so just for debug purposes, I'm going to make a boolean here on the enemy class. 15:22.020 --> 15:25.590 So I'm going to say bool be highlighted. 15:26.850 --> 15:28.890 Set it to false by default. 15:28.890 --> 15:34.800 Expose it with a u property and make it blueprint read only. 15:35.490 --> 15:40.140 And all I'm going to do is set this to true and highlight. 15:41.000 --> 15:50.360 Actor, so be highlighted equals true and set it to false in Unhighlight actor so be highlighted equals 15:50.360 --> 15:51.200 false here. 15:51.200 --> 15:55.940 And I'm going to go ahead and run and debug mode and launch the editor. 15:55.940 --> 16:00.440 And we'll draw some debug spheres when the enemy's highlighted. 16:00.770 --> 16:05.000 So I'm going to find my BP spear Goblin. 16:05.000 --> 16:09.440 Open up that blueprint and simply check here. 16:09.440 --> 16:12.920 In event tick are highlighted variable. 16:12.920 --> 16:18.110 So I'm going to get highlighted I'm going to branch off based on this. 16:18.110 --> 16:20.840 And if true I'm going to draw a debug sphere. 16:20.840 --> 16:23.150 So we'll say draw debug sphere. 16:25.090 --> 16:29.740 And we'll draw it for a single frame so duration will be zero. 16:29.770 --> 16:36.910 I'm going to use Get Actor location for the center and I'll leave the radius at. 16:36.910 --> 16:40.180 We'll make it 50 and I'll make it red. 16:41.920 --> 16:48.010 Okay, now, before we test this out, and you may have gotten tripped up on this part of the challenge, 16:48.010 --> 16:54.400 we have to make sure that our enemy is set to block the visibility channel, as that's what we're tracing 16:54.400 --> 16:56.290 with from our player controller. 16:56.290 --> 17:04.270 So we can select the mesh itself and we can go into the collision presets. 17:04.270 --> 17:07.600 And by default we have it set to character mesh. 17:07.600 --> 17:12.520 We're going to have to change that to custom and set visibility to block. 17:12.520 --> 17:14.740 And that way we should be able. 17:15.640 --> 17:17.710 To block the visibility channel. 17:18.470 --> 17:20.330 With our goblin mash. 17:21.220 --> 17:23.110 Now if I press play. 17:25.210 --> 17:28.780 And I enter the console command show collision. 17:28.780 --> 17:32.140 We'll see that that goblin does have a physics asset. 17:32.140 --> 17:34.420 So that's what we should be tracing against. 17:34.960 --> 17:40.210 I'll go ahead and remove that and hide those collision shapes. 17:40.210 --> 17:46.480 And as I highlight I get my sphere. 17:46.900 --> 17:48.580 So it looks like it's working. 17:48.580 --> 17:51.940 Now what happens if we have multiple goblins. 17:51.940 --> 17:53.350 We could test all the use cases. 17:53.350 --> 17:55.870 So I'm going to have two goblins next to each other. 17:56.200 --> 17:58.270 And I'm going to highlight one. 17:58.480 --> 17:59.650 Highlight the other. 17:59.650 --> 18:01.300 So that case is working. 18:01.300 --> 18:03.790 So this seems to be working quite nicely. 18:03.790 --> 18:06.400 Now we had to put this on Goblin spear. 18:06.400 --> 18:11.770 So if we drag out the goblin slingshot for example it's not going to work. 18:11.770 --> 18:17.020 If we drag that out and press play, well it's not doing anything. 18:17.020 --> 18:18.520 We put that logic in event. 18:18.550 --> 18:23.560 Tick for Goblin spear, not the goblin slingshot. 18:23.560 --> 18:26.140 Unfortunately, that's not going to work. 18:26.140 --> 18:32.530 Now, there may be things that we wish to implement in blueprint for all enemies, which means that 18:32.530 --> 18:39.010 we should have an enemy base class that all enemy blueprints should be derived from. 18:39.010 --> 18:42.010 Right now, all enemy blueprints are derived. 18:42.010 --> 18:50.470 If we go to class settings from Aura Enemy, they should all be derived from a common enemy blueprint. 18:50.470 --> 18:56.710 And that way when we have the situation where we want to implement something in blueprint for all enemies, 18:56.710 --> 19:00.310 they'll all get that blueprint logic inherited. 19:00.310 --> 19:07.540 So that's something that we're going to keep in mind and plan on doing as we continue with this project. 19:07.540 --> 19:15.280 For now, we know that our highlighting is working, which is great as indicated by our debug spheres. 19:15.280 --> 19:16.570 So that's awesome. 19:16.570 --> 19:22.060 We no longer need that because we are going to highlight our enemy and a much more interesting way. 19:22.060 --> 19:23.500 And we'll do that next. 19:23.980 --> 19:25.000 I'll see you soon.