WEBVTT 00:06.980 --> 00:08.210 Welcome back. 00:08.330 --> 00:16.010 Now that we have inputs and we have callbacks that we can use to respond to those inputs, we can start 00:16.010 --> 00:17.810 implementing our abilities. 00:17.930 --> 00:22.910 But additionally, we can implement other capabilities for our character. 00:22.910 --> 00:30.020 And because this is a top down project, one important gameplay mechanic we should think about is Click 00:30.020 --> 00:30.740 to Move. 00:30.770 --> 00:39.110 This is a common feature of lots of top down games and we have a unique opportunity to figure out how 00:39.110 --> 00:40.940 to make this happen for our game. 00:41.540 --> 00:47.120 Now it just so happens that Unreal Engine provides a top down template project. 00:47.420 --> 00:54.110 This gives us a nice example of how you might go about implementing a basic top down. 00:54.110 --> 00:56.570 And in this project we have click to move. 00:56.570 --> 01:04.250 If I click on the ground, the character will move to the location I clicked on and if I click and hold, 01:04.280 --> 01:08.360 then the character will follow my mouse cursor. 01:08.450 --> 01:15.710 So this is a pretty good basic click to move, But the top down templates implementation of Click to 01:15.710 --> 01:18.610 Move has one important limitation. 01:18.620 --> 01:26.110 We can quickly discover that limitation by changing our number of players to two and changing the net 01:26.150 --> 01:33.080 mode from standalone to one of the other options such as play as listen server or play as client. 01:33.080 --> 01:39.440 If I choose one of those and press play now we'll have two characters in multiplayer. 01:39.740 --> 01:47.970 Now if I click and release, my character will not move to the location that I clicked on. 01:47.970 --> 01:51.320 But if I click and hold, it'll work just fine. 01:51.330 --> 01:56.400 Now I chose to play as client, meaning both of these are clients. 01:56.400 --> 02:02.130 If I click in the main viewport and release, the character will not move. 02:02.160 --> 02:06.390 It'll move a little bit, but when I release the mouse button, it stops moving. 02:06.390 --> 02:08.580 If I hold it down though, everything works. 02:08.580 --> 02:09.450 Okay. 02:09.960 --> 02:19.050 Now if I change this to play as listen server and press play, then one of my characters is the host. 02:19.140 --> 02:20.880 The one in the big window. 02:20.910 --> 02:23.220 The one in the small window is the client. 02:23.250 --> 02:28.320 Now the client can click and release and nothing happens. 02:28.320 --> 02:34.980 But if I click and release in the big window, well then I get that nice auto run behavior. 02:36.030 --> 02:44.370 And if I show it in two windows, you'll see that I can click and release and the server character auto 02:44.370 --> 02:44.760 runs. 02:44.760 --> 02:49.700 And it works in multiplayer, but if I click and release on the client, it does not work. 02:49.710 --> 02:52.120 So why is that? 02:52.140 --> 02:58.980 It's a little disappointing that the top down project doesn't give us fully working click to move behavior 02:58.980 --> 03:03.990 just out of the box, but we can find out why by looking at the code. 03:04.020 --> 03:13.470 Here's the top down template project and the movement is set up in the top down player controller and 03:13.470 --> 03:21.270 the top down player controller has some callbacks bound to input actions Using enhanced input. 03:21.300 --> 03:29.190 We have a set destination click action and we have a number of functions bound to it. 03:29.220 --> 03:34.350 We have one for started, triggered, completed and cancelled. 03:34.860 --> 03:39.490 Now for started and all we have here is stop movement. 03:39.490 --> 03:44.560 So it's in set on destination triggered which is called every frame. 03:44.560 --> 03:48.820 As long as the input is held down that we actually start doing stuff. 03:48.850 --> 03:55.690 The very frame that we begin clicking that left mouse button, all we get is this call to stop movement. 03:55.720 --> 03:57.070 What does that do? 03:57.100 --> 04:01.260 Well, we'll find out why as soon as we analyze the code here. 04:01.270 --> 04:05.320 So on set, destination triggered is fired every frame. 04:05.320 --> 04:10.420 As long as input is held down, you'll see that we have this member variable. 04:10.420 --> 04:18.220 It's a float called follow time and it's getting the delta seconds and adding that to follow time. 04:18.220 --> 04:23.560 So in other words, we have this running time that's incrementing with Delta time, every frame. 04:23.560 --> 04:30.820 Then it creates a hit result, creates a local Boolean set to false called hit successful and then gets 04:30.820 --> 04:32.590 the hit results under finger. 04:32.590 --> 04:39.970 If B is touch is true, this is for mobile, otherwise it just gets the hit result under the cursor 04:39.970 --> 04:42.070 and fills in that hit result. 04:42.100 --> 04:47.680 Now if there was a successful hit, it takes that hit result and caches that location. 04:47.680 --> 04:54.220 So wherever we click if we got a successful hit result under that cursor we store that world location 04:54.220 --> 04:57.310 in this cached destination vector. 04:57.490 --> 05:04.090 Now, after storing that location, we see the comments as move towards mouse pointer or touch where 05:04.090 --> 05:05.380 it gets the pawn. 05:05.380 --> 05:13.090 As long as it's not a null pointer, it calculates a direction by taking that cached destination and 05:13.090 --> 05:16.750 getting the controlled pawns actor location. 05:16.870 --> 05:23.200 And if we take the subtraction between these two vectors, we get a vector from the controlled pawn 05:23.200 --> 05:25.480 to the cached destination. 05:25.480 --> 05:27.610 It then calls get safe normal. 05:27.610 --> 05:33.280 So we have a normalized vector pointing in the direction that we want to run in. 05:33.280 --> 05:36.940 And then we call add movement input passing in that direction. 05:36.940 --> 05:38.760 Now this is called every frame. 05:38.770 --> 05:44.470 So as long as this function is being called, we're calling add movement input here. 05:44.470 --> 05:52.150 And this is called as long as input is being held down and add movement input moves the pawn through 05:52.150 --> 05:54.280 the Pawns movement component. 05:54.460 --> 05:55.110 Right? 05:55.150 --> 06:00.040 We can right click and go to the definition for add movement component. 06:00.040 --> 06:07.450 And as we can see, it takes whatever movement component is assigned to this pawn and it uses that to 06:07.450 --> 06:08.320 add movement. 06:08.350 --> 06:14.650 Now the cool thing about movement components is that they have built in replication capabilities already. 06:14.650 --> 06:20.740 So that's why if we're holding our mouse cursor down, we get replicated movement. 06:20.770 --> 06:25.750 We can hold the mouse cursor down on the client and the server sees that movement. 06:25.750 --> 06:29.650 Just to kind of show you that again, here's the client. 06:29.650 --> 06:33.520 And if I click and hold down, you can see that the movement looks good. 06:33.520 --> 06:38.080 It's smooth, everything works fine, but it's that auto run. 06:38.080 --> 06:43.600 If I click and release that auto run doesn't work, but it works on the server, I can click and release 06:43.600 --> 06:46.630 on the server and auto run works. 06:46.780 --> 06:51.040 So there must be something that is done differently in that case. 06:51.130 --> 06:58.600 Well, we have on set destination released and as we saw in setup input component here, this function 06:58.600 --> 07:03.850 is bound to our input action with completed for the trigger event. 07:03.850 --> 07:09.640 That means when we release our input, then this callback will be executed. 07:09.670 --> 07:15.550 Now we see that the comment says if it was a short press and we checked that follow time and see if 07:15.550 --> 07:17.710 it's less than a short press threshold. 07:17.710 --> 07:24.640 So there's some amount of time that we want to consider a short press because at the end of this function 07:24.640 --> 07:26.560 we see that we reset, follow time. 07:26.560 --> 07:32.770 So as we release the mouse button, that follow time is going to be reset to zero. 07:32.770 --> 07:34.870 But before that, we check to see if. 07:34.900 --> 07:36.520 It was a short press. 07:36.670 --> 07:42.370 Otherwise, we've been holding the mouse cursor down for some time, which means we've been doing this 07:42.370 --> 07:48.910 functionality here and set destination triggered, which is basically moving the pawn with add movement 07:48.910 --> 07:49.180 input. 07:49.210 --> 07:55.810 We see that this works in multiplayer just fine, but if it was a short press, we're handling movement 07:55.810 --> 07:57.080 in a different way. 07:57.100 --> 08:05.860 It's using UI, Blueprint Helper library calling simple move to location, passing in that cached destination. 08:05.860 --> 08:15.010 And it also handles spawning a system, a Niagara system at the location that cached destination location. 08:15.010 --> 08:20.110 And that system is what we see here with these little arrows. 08:20.110 --> 08:21.640 That's a Niagara system. 08:21.640 --> 08:27.120 We're spawning that right here as we call simple move to location. 08:27.130 --> 08:30.640 Now simple move to location is an AI function. 08:30.640 --> 08:33.520 It's in the AI Blueprint Helper library. 08:33.520 --> 08:35.120 And I moved. 08:35.120 --> 08:39.440 Two functions are not designed to be called from a client. 08:39.470 --> 08:43.370 They're meant to be called on the server for AI characters. 08:43.370 --> 08:51.350 So if you have an AI character controlled by the server, you can use simple move to location and if 08:51.350 --> 08:57.680 that AI character has its movement replicated, it'll replicate down to all clients, no problem. 08:57.680 --> 09:02.150 But for a human controlled character, this is not going to work. 09:02.180 --> 09:06.290 It works locally, but there's no multiplayer replication built in. 09:06.290 --> 09:10.760 It's not like calling add movement input on a movement component. 09:10.790 --> 09:14.180 This has all sorts of lag compensation built in. 09:14.180 --> 09:21.710 It has prediction, we can call it client side and we'll see our character move immediately and the 09:21.710 --> 09:25.520 server will receive that information through the movement component. 09:25.520 --> 09:28.310 It's all very nice and smooth but simple. 09:28.310 --> 09:31.040 Move to location is not going to do that. 09:31.040 --> 09:32.480 It's not going to work. 09:32.660 --> 09:35.570 So we can't use simple move to location. 09:35.570 --> 09:43.310 If we want to just click and have our character move automatically to a location and just expect that 09:43.310 --> 09:44.660 to work in multiplayer. 09:44.660 --> 09:51.050 And that's a shame because when we are using that functionality, we get some interesting pathfinding 09:51.050 --> 09:52.190 capabilities. 09:52.190 --> 09:55.460 Let's say that I want to click on the other side of this pillar. 09:55.460 --> 10:00.980 Well, if I do it on the server, we're using simple move to location that works on the server so I 10:00.980 --> 10:03.770 can click and it'll go around the pillar. 10:03.770 --> 10:05.930 It finds its way around it. 10:05.930 --> 10:07.880 It's using pathfinding. 10:08.360 --> 10:10.850 That's because there's a nav mesh bounds volume. 10:10.850 --> 10:15.950 If we press P, we can see it that's required for any of these. 10:15.980 --> 10:22.340 I move to type functions to work, but again, it's a shame that we can't just use it and expect this 10:22.340 --> 10:26.990 to work in multiplayer as we see the top down template doesn't even do this. 10:26.990 --> 10:31.490 We can click and nothing very exciting happens. 10:31.490 --> 10:36.730 We have to click and hold to move our clients in Multiplayer. 10:36.730 --> 10:40.840 So that's a limitation of the top down template. 10:40.840 --> 10:44.800 And that means we can't just use the top down template code. 10:44.800 --> 10:48.580 We have to do something a little bit more sophisticated than that. 10:48.790 --> 10:54.970 So what we've learned from this analysis is that the top down template uses simple move to location. 10:54.970 --> 11:02.260 If it was a short press, it does not work in multiplayer only AI controlled characters on the server 11:02.260 --> 11:04.480 or the hosting player. 11:04.510 --> 11:08.860 Now it does use add movement input if input is held down. 11:08.860 --> 11:14.830 And in that case this works in multiplayer as we've seen, and it requires constant input. 11:14.830 --> 11:21.280 In other words, we're calling add movement input every single frame passing in a movement direction. 11:21.280 --> 11:23.140 Now this works locally. 11:23.140 --> 11:29.830 If we're on a client and we see that movement on the server and it is indeed replicated to all other 11:29.830 --> 11:36.920 clients, even though we didn't test out that case, it does work with multiple other clients as well. 11:36.920 --> 11:41.390 So for Argus Project, how are we going to get the best of both worlds? 11:41.390 --> 11:46.670 How are we going to get Click to Move behavior where we can click and do a short press? 11:46.670 --> 11:52.850 In other words, click and release immediately and see our character move to that location. 11:52.850 --> 11:57.950 Even taking advantage of pathfinding, moving around obstacles and things like that. 11:57.950 --> 11:59.450 That's what we want to do. 11:59.810 --> 12:02.780 Well, we know that we must use add movement input. 12:02.810 --> 12:05.840 We have to do this on a per frame basis. 12:05.870 --> 12:12.800 As long as our character is moving, we have to constantly pass in the correct direction and add movement. 12:12.800 --> 12:16.610 Input will work in multiplayer if we can manage to do that. 12:17.270 --> 12:19.820 So we need a direction each frame. 12:19.970 --> 12:22.550 So let's think about how we can do this. 12:23.300 --> 12:26.210 We have our pawn and we have our mouse cursor. 12:26.330 --> 12:31.910 Now our pawn has a location and our mouse cursor has a world location. 12:31.910 --> 12:34.400 If we get the hit, result underneath it. 12:34.430 --> 12:41.390 Now if we have our character's location and the mouse cursor hit result location, this forms a straight 12:41.390 --> 12:44.400 line provided there are no obstacles in the way. 12:44.420 --> 12:51.500 So it's fairly easy to take these two locations and calculate a direction and then we can call add movement 12:51.500 --> 12:54.920 input every frame as long as we're supposed to be moving. 12:54.920 --> 13:00.320 And that's going to move our character in the correct direction, and that works in multiplayer. 13:00.350 --> 13:07.400 Now this is a pretty easy case to take care of, but there are complications in multiplayer. 13:07.400 --> 13:09.820 We may have things in the way. 13:09.830 --> 13:13.210 Let's say we have a pillar or some obstacle, right? 13:13.220 --> 13:20.210 And the straight line between our character and the mouse cursor world hit location would go through 13:20.210 --> 13:21.470 that obstacle. 13:21.470 --> 13:23.910 Now we can't just move in that direction. 13:23.910 --> 13:29.610 Our character is going to hit that wall and still continue trying to move through the wall and it's 13:29.610 --> 13:31.110 going to look very bad. 13:31.140 --> 13:33.120 We need some sort of pathfinding. 13:33.120 --> 13:39.150 We need a way to find points that will create a path for us that will go around the pillar. 13:39.360 --> 13:43.710 Now, there are functions that we can use to generate this type of path. 13:43.710 --> 13:49.790 That's not a problem, but this can result in some less than desirable behavior as well. 13:49.800 --> 13:57.480 You see, we can easily calculate a direction from our character's current location to the next point 13:57.480 --> 13:58.830 on this path. 13:59.220 --> 14:05.700 That's a straight line and we can move that character in that straight line until it reaches that second 14:05.700 --> 14:09.450 point, at which point the direction changes. 14:09.450 --> 14:15.210 And as soon as we've reached that second point, we change the character's direction and continue calling 14:15.240 --> 14:20.580 add movement input until we reach the next point, at which point the direction changes again. 14:20.760 --> 14:27.180 Now, this can result in an abrupt change in orientation and that can be less than desirable. 14:27.210 --> 14:33.180 Consider the case where we're looking down on our character from directly above and we can see the top 14:33.180 --> 14:38.790 of the obstacle that's in the way, and we generate a path to find our way around it. 14:38.880 --> 14:46.560 Now our direction will be from the character's location to that second point in the path, and that's 14:46.560 --> 14:47.460 a straight line. 14:47.460 --> 14:52.170 And as soon as we hit that point, the change in orientation is abrupt. 14:52.200 --> 14:55.140 We might even see it appear to snap. 14:55.290 --> 15:01.470 And as soon as we reach the next point, our change in direction is abrupt yet again, and this can 15:01.470 --> 15:03.060 be less than desirable. 15:03.300 --> 15:08.940 It would be nice if we could have a smooth curve for our path. 15:08.970 --> 15:10.560 Now this is possible. 15:10.560 --> 15:18.780 We can create a spline out of a system of points that we've generated and a spline is going to smooth 15:18.780 --> 15:22.260 itself out and have a nice round curve like this. 15:22.710 --> 15:30.900 Now, if we can generate a spline from some path points, then we have the ability to get the forward 15:30.900 --> 15:38.730 direction on the spline at any point and it's always going to be tangent to that spline curve. 15:38.760 --> 15:43.590 So as we're moving along the spline, that direction can be smooth. 15:43.620 --> 15:45.780 We'll never have an abrupt change. 15:45.780 --> 15:53.410 We'll always have a smooth, continuous change in direction as we're moving along the spline. 15:53.430 --> 16:01.420 So this is a nice solution to this problem if we can manage to generate a path to move along. 16:01.440 --> 16:09.150 We can create a spline that will be a nice smooth curve that will allow us to navigate around obstacles 16:09.150 --> 16:10.560 in a smooth manner. 16:10.710 --> 16:16.310 And that's the approach I'd like to take for our click to move mechanic in this game. 16:16.320 --> 16:21.420 So we'll get started with implementing this method in the next video. 16:21.720 --> 16:22.870 I'll see you soon.