1 00:00:04,080 --> 00:00:05,730 ‫Hello and welcome back. 2 00:00:05,760 --> 00:00:10,380 ‫Now we're ready to rotate the turret and we'd like to do this using the mouse. 3 00:00:10,380 --> 00:00:14,790 ‫And that hit location from the trace hit we've done in the previous video. 4 00:00:14,880 --> 00:00:22,200 ‫So as I'm moving my mouse cursor, the turret is rotating and facing the direction of the mouse cursor. 5 00:00:22,320 --> 00:00:28,110 ‫And even when I click in the viewport and begin to play, I can still move the mouse cursor around to 6 00:00:28,110 --> 00:00:31,080 ‫rotate the turret and set its direction. 7 00:00:31,110 --> 00:00:35,850 ‫This will allow me to aim when I have the capability of firing projectiles. 8 00:00:35,880 --> 00:00:36,200 ‫Okay. 9 00:00:36,240 --> 00:00:41,770 ‫So to achieve this, we need to find the direction that we want our turret to point in. 10 00:00:41,790 --> 00:00:46,410 ‫And once we've found that direction, then we can set the turret mesh rotation. 11 00:00:46,500 --> 00:00:52,470 ‫Now, in order to get the direction that we'd like the turret to point in, we need to do a little bit 12 00:00:52,470 --> 00:00:53,500 ‫of vector math. 13 00:00:53,520 --> 00:00:59,570 ‫What we're looking for is a vector from the tank turret to our trace hit location. 14 00:00:59,580 --> 00:01:05,940 ‫Now we can easily get the location of our tank or any of its components, such as the location of the 15 00:01:05,940 --> 00:01:06,960 ‫tank's turret. 16 00:01:06,990 --> 00:01:09,600 ‫We'll call this location, turret, location. 17 00:01:09,600 --> 00:01:13,440 ‫And we also know how we can get the location of the trace head. 18 00:01:13,470 --> 00:01:15,800 ‫We'll call this trace hit location. 19 00:01:15,810 --> 00:01:20,760 ‫What we're interested in is the vector from turret location to trace hit location. 20 00:01:20,760 --> 00:01:23,100 ‫We'll call this vector to target. 21 00:01:23,130 --> 00:01:27,030 ‫Now the vector math to get to target is actually quite simple. 22 00:01:27,060 --> 00:01:33,120 ‫To get a vector from a start point to an endpoint is always the endpoint minus the start point. 23 00:01:33,420 --> 00:01:39,270 ‫So if we take our trace, hit location and subtract the vector turret location, then the vector that 24 00:01:39,270 --> 00:01:41,620 ‫results from this is to target. 25 00:01:41,640 --> 00:01:47,160 ‫Now, once we have the two target direction vector, we want to convert that to a rotation so we can 26 00:01:47,160 --> 00:01:49,530 ‫set the rotation of the tank's turret. 27 00:01:49,530 --> 00:01:53,750 ‫And the vector type has a built in function called rotation. 28 00:01:53,760 --> 00:02:01,230 ‫So if we took our to target vector and called rotation on it, this would return an F rotator corresponding 29 00:02:01,230 --> 00:02:02,260 ‫to that direction. 30 00:02:02,280 --> 00:02:04,430 ‫Now we do need to keep something in mind. 31 00:02:04,440 --> 00:02:11,160 ‫The trace hit result is often going to be on the floor and the vector from the tank turret to the trace 32 00:02:11,160 --> 00:02:14,620 ‫hit result is not going to be parallel with the ground. 33 00:02:14,640 --> 00:02:20,850 ‫This means that if we set the tank's turret rotation to the rotator we get from that direction vector, 34 00:02:20,850 --> 00:02:26,790 ‫we might get something like this where the turret is angled down towards the ground, but we don't want 35 00:02:26,790 --> 00:02:29,310 ‫the tanks turret to rotate downward. 36 00:02:29,310 --> 00:02:31,350 ‫We want it to still point forward. 37 00:02:31,350 --> 00:02:33,780 ‫So this is the result that we want. 38 00:02:33,810 --> 00:02:39,180 ‫In other words, we only want to change the yea component of the tank's turret rotation. 39 00:02:39,180 --> 00:02:44,550 ‫So that way it's pointing in the correct direction but still remains parallel to the ground. 40 00:02:44,550 --> 00:02:51,060 ‫We've only changed its yaw, so let's hop back into VS code and create a function for rotating the tank 41 00:02:51,060 --> 00:02:51,600 ‫turret. 42 00:02:51,630 --> 00:02:57,210 ‫Now we're going to be rotating the turret on the tank, but we'd also like to rotate the turret on our 43 00:02:57,210 --> 00:03:04,290 ‫tower enemy and the tower is soon going to be created derived from base pon, which means if we create 44 00:03:04,290 --> 00:03:08,820 ‫a rotate turret function we can place it here in the base pong class. 45 00:03:08,820 --> 00:03:12,930 ‫So that way both the tank and the tower will inherit this function. 46 00:03:12,930 --> 00:03:18,480 ‫Since we plan on using it in both the tower and the tank, we can make this function protected. 47 00:03:18,720 --> 00:03:24,630 ‫So I'm going to add a protected section and any functions and variables we place in the protected section 48 00:03:24,630 --> 00:03:29,220 ‫will be accessible in these child classes, but not in any other classes. 49 00:03:29,220 --> 00:03:32,580 ‫So it's almost as restricted as private variables. 50 00:03:32,580 --> 00:03:34,860 ‫Now this function can return void. 51 00:03:34,860 --> 00:03:37,710 ‫I'm going to call this rotate turret. 52 00:03:38,850 --> 00:03:44,690 ‫And in order to rotate the turret, I'm going to need a sort of destination to look at. 53 00:03:44,700 --> 00:03:49,620 ‫This can be a f vector and we can call this look at target. 54 00:03:49,620 --> 00:03:56,490 ‫So the idea is if we have a function that we can pass in some sort of location in the world, then the 55 00:03:56,490 --> 00:04:00,360 ‫function should result in rotating the turret towards that location. 56 00:04:00,360 --> 00:04:04,680 ‫So let's go ahead and provide a function definition for rotate turret. 57 00:04:04,680 --> 00:04:11,280 ‫So here in base pawn CP just under the constructor, I'm going to implement rotate turret. 58 00:04:11,280 --> 00:04:16,680 ‫And of course I need the a base pawn class name with the scope resolution operator here. 59 00:04:16,680 --> 00:04:21,180 ‫So now that I have rotate turret, let's think about how we're going to implement this. 60 00:04:21,180 --> 00:04:28,320 ‫The first thing we need is that to target vector the vector from the turret component to the trace hit 61 00:04:28,320 --> 00:04:30,120 ‫result under the mouse cursor. 62 00:04:30,120 --> 00:04:38,070 ‫So this can be a local F vector called to target and we're going to set it equal to the result of some 63 00:04:38,070 --> 00:04:38,970 ‫vector math. 64 00:04:38,970 --> 00:04:43,350 ‫Remember, it's going to be the destination minus the starting point. 65 00:04:43,350 --> 00:04:50,910 ‫And the destination is look at target and the starting point is going to be the location of the tank's 66 00:04:50,910 --> 00:04:54,030 ‫turret, in other words, the location of turret mesh. 67 00:04:54,030 --> 00:04:59,880 ‫So we can say turret mesh and we can get the turret mesh location. 68 00:04:59,880 --> 00:05:07,290 ‫Now the way to get the world location of a component is with this function get component location. 69 00:05:07,290 --> 00:05:09,630 ‫It belongs to the use scene component class. 70 00:05:09,630 --> 00:05:11,460 ‫So all scene components have it. 71 00:05:11,460 --> 00:05:15,690 ‫So from the turret mesh we'll call get component location. 72 00:05:16,340 --> 00:05:23,600 ‫So look at target minus the turret mesh location gives us the vector from the turret mesh to the lookout 73 00:05:23,600 --> 00:05:24,290 ‫target. 74 00:05:24,320 --> 00:05:30,590 ‫Now, as I mentioned, we can get an EF rotator from to target using the F vectors rotation function. 75 00:05:30,590 --> 00:05:37,100 ‫So we're going to make an F rotator and we can call this look at rotation and we'll set this equal to 76 00:05:37,100 --> 00:05:40,100 ‫to target dot rotation. 77 00:05:40,280 --> 00:05:41,570 ‫That's a function call. 78 00:05:41,570 --> 00:05:46,700 ‫So now we have the rotator corresponding to this to target direction vector. 79 00:05:46,700 --> 00:05:49,550 ‫But the thing is we only care about the YA. 80 00:05:49,550 --> 00:05:51,680 ‫We don't want to change the pitch or role. 81 00:05:51,680 --> 00:05:57,290 ‫We only want to rotate the turret around the z axis and keep it parallel with the ground. 82 00:05:57,290 --> 00:05:59,420 ‫Now we can do this any number of ways. 83 00:05:59,420 --> 00:06:05,870 ‫For one, we can take look at rotation, pitch and zero that out. 84 00:06:05,870 --> 00:06:08,180 ‫In other words, set it equal to zero. 85 00:06:08,210 --> 00:06:14,240 ‫We can also take look at rotation dot role and zero that out as well. 86 00:06:14,240 --> 00:06:21,020 ‫Now after we've set pitch and roll to zero, we have the rotation we want, which is only the component. 87 00:06:21,020 --> 00:06:22,460 ‫This is one way to do it. 88 00:06:22,460 --> 00:06:26,450 ‫Another would be to use one of the F rotator constructor overloads. 89 00:06:26,450 --> 00:06:34,820 ‫If we said f rotator with parentheses and passed in some values such as zero point F for the first and 90 00:06:34,820 --> 00:06:38,300 ‫the pop up is telling me that that first input is the pitch. 91 00:06:38,300 --> 00:06:43,880 ‫And then for the ya we can use to target rotation. 92 00:06:44,330 --> 00:06:44,990 ‫Yeah. 93 00:06:44,990 --> 00:06:47,960 ‫And then for the role we could use zero dot F. 94 00:06:47,960 --> 00:06:55,820 ‫Now what this does is creates a new F rotator with zero for the pitch, zero for the role and the component 95 00:06:55,820 --> 00:06:59,420 ‫of the rotator returned by two target rotation. 96 00:06:59,420 --> 00:07:05,300 ‫So the value returned by this would give us the same result as what we did here with these three lines. 97 00:07:05,300 --> 00:07:11,990 ‫So since this is a little bit more compact and elegant, I think I'd rather use this so we can initialize 98 00:07:11,990 --> 00:07:19,370 ‫the look at rotation vector with the F rotator returned by calling the F rotator constructor like this. 99 00:07:19,370 --> 00:07:21,380 ‫So I'm going to remove this line down here. 100 00:07:21,380 --> 00:07:23,360 ‫And now we have look at rotation. 101 00:07:23,360 --> 00:07:29,000 ‫Now the last thing to do in this function is to set the rotation for the turret mash. 102 00:07:29,000 --> 00:07:36,440 ‫Now we can set the rotation for a given component using this function set world rotation again, it 103 00:07:36,440 --> 00:07:38,270 ‫belongs to use scene component. 104 00:07:38,270 --> 00:07:44,300 ‫And the reason we're using set word rotation rather than adding some sort of local rotation offset is 105 00:07:44,300 --> 00:07:50,420 ‫because we have a rotation in world space two target is a world space direction vector. 106 00:07:50,420 --> 00:07:56,000 ‫We're taking the turret mesh location in world space and subtracting the look at target location in 107 00:07:56,000 --> 00:07:56,750 ‫world space. 108 00:07:56,750 --> 00:07:58,850 ‫So this is a world space direction. 109 00:07:58,850 --> 00:08:02,450 ‫Therefore the look at rotation is a world space rotation. 110 00:08:02,450 --> 00:08:06,140 ‫So we're going to use set world rotation on the turret mesh. 111 00:08:06,290 --> 00:08:13,280 ‫So we'll say turret mesh, set world rotation and we're going to pass in look at rotation. 112 00:08:13,280 --> 00:08:19,550 ‫So now we have a function that can take any target in the world and turn the turret mesh to look at 113 00:08:19,550 --> 00:08:22,550 ‫it, but it won't rotate the mesh downwards. 114 00:08:22,550 --> 00:08:28,100 ‫It's only going to change its yaw, so it'll rotate in a way that a tank turret should rotate. 115 00:08:28,100 --> 00:08:31,100 ‫So we now have a function to rotate the turret. 116 00:08:31,130 --> 00:08:36,980 ‫I'm going to challenge you to call this function to set that turret rotation, call the rotate turret 117 00:08:36,980 --> 00:08:38,870 ‫function in the tank class. 118 00:08:38,870 --> 00:08:40,730 ‫This is a protected function. 119 00:08:40,730 --> 00:08:43,070 ‫So the tank class has access to it. 120 00:08:43,070 --> 00:08:49,220 ‫Now rotate turret takes an F vector, the look at target, you're going to use that impact point in 121 00:08:49,220 --> 00:08:51,410 ‫the F hit result from our line trace. 122 00:08:51,410 --> 00:08:57,170 ‫So I'm going to leave it up to you to find the correct place in code to call this function. 123 00:08:57,410 --> 00:09:00,920 ‫So pause the video and place the rotate turret function. 124 00:09:00,920 --> 00:09:02,870 ‫Call in the tank class. 125 00:09:06,000 --> 00:09:06,150 ‫Okay. 126 00:09:06,300 --> 00:09:09,960 ‫So we have our rotate turret function and we're ready to call it. 127 00:09:10,140 --> 00:09:18,200 ‫I'm going to go into tank up and here's my tick function inside the if check for player controller ref. 128 00:09:18,210 --> 00:09:24,870 ‫I have my hit result and after a get hit result under cursor has been called, the hit result will have 129 00:09:24,870 --> 00:09:25,860 ‫valid data. 130 00:09:25,860 --> 00:09:30,480 ‫In fact, we're using that hit result impact point and draw debug sphere. 131 00:09:30,510 --> 00:09:35,370 ‫Now since I don't need to draw the debug sphere anymore, I'm going to go ahead and delete that. 132 00:09:35,370 --> 00:09:39,900 ‫And instead I'm going to call our protected function rotate turret. 133 00:09:39,900 --> 00:09:45,750 ‫And for the look at target, I'm going to pass in hit result dot impact point. 134 00:09:47,140 --> 00:09:53,320 ‫So now every frame we're going to be rotating the turret towards that impact point from our hit result. 135 00:09:53,350 --> 00:09:59,050 ‫Now before I compile this, I'm no longer using draw debug helpers, so I'm going to go ahead and remove 136 00:09:59,050 --> 00:10:00,130 ‫that header file. 137 00:10:00,340 --> 00:10:00,820 ‫Okay. 138 00:10:00,850 --> 00:10:02,590 ‫Now I'm ready to compile. 139 00:10:02,970 --> 00:10:03,360 ‫Okay. 140 00:10:03,370 --> 00:10:05,050 ‫I'm back here in the editor. 141 00:10:05,080 --> 00:10:09,440 ‫Let's go ahead and hit play and check it out. 142 00:10:09,460 --> 00:10:11,460 ‫This is amazing. 143 00:10:11,470 --> 00:10:12,910 ‫I can still roll around. 144 00:10:12,910 --> 00:10:18,910 ‫I can move my mouse and the turret is rotating wherever I move my mouse cursor. 145 00:10:18,910 --> 00:10:20,350 ‫So this is awesome. 146 00:10:20,600 --> 00:10:25,750 ‫Okay, so before we wrap this up, I'd like to just address a couple of issues. 147 00:10:25,750 --> 00:10:28,900 ‫I want this to be nice and polished and looking great. 148 00:10:28,930 --> 00:10:35,680 ‫Now, the first issue happens when I move the mouse cursor close to the center of the tank and then 149 00:10:35,680 --> 00:10:36,890 ‫pass through it. 150 00:10:36,910 --> 00:10:42,670 ‫You'll see that at some point that rotation sort of snaps very rapidly. 151 00:10:42,670 --> 00:10:48,250 ‫And if we kind of move the mouse around in a haphazard manner, well, that doesn't look too great. 152 00:10:48,250 --> 00:10:49,480 ‫It's snapping. 153 00:10:49,480 --> 00:10:50,890 ‫We don't have smooth movement. 154 00:10:50,890 --> 00:10:52,270 ‫So that's one issue. 155 00:10:52,300 --> 00:10:59,890 ‫Now, the other issue is if I click and I roll around and I go up to the edge, I'll see that my turret 156 00:10:59,890 --> 00:11:03,750 ‫snaps in the other direction when I move my mouse cursor up. 157 00:11:03,760 --> 00:11:05,730 ‫So what's going on there? 158 00:11:05,740 --> 00:11:06,910 ‫Well, let's find out. 159 00:11:06,910 --> 00:11:10,240 ‫We'll go back to VS Code and I'd like to get my debug sphere back. 160 00:11:10,240 --> 00:11:16,240 ‫So back here in Tank, I'm going to go to the tick function right before rotate turret and once again 161 00:11:16,240 --> 00:11:19,240 ‫I'm going to call draw debug sphere. 162 00:11:19,450 --> 00:11:26,380 ‫Now for the world I'm passing in get world for the center I'm passing in hit result dot impact point 163 00:11:26,380 --> 00:11:35,350 ‫for the radius I'll use 25 dot F segments can be 12, color can be F color red persistent lines can 164 00:11:35,350 --> 00:11:38,440 ‫be false and lifetime can be negative one. 165 00:11:38,440 --> 00:11:40,480 ‫So same thing we did before. 166 00:11:40,690 --> 00:11:42,280 ‫So I'm going to save this notice. 167 00:11:42,280 --> 00:11:48,700 ‫I'm not adding the header file back up there and that's because debug helpers actually is included by 168 00:11:48,700 --> 00:11:50,830 ‫default, so we don't technically need it. 169 00:11:50,830 --> 00:11:56,740 ‫I'm just going to save jump back in the editor, do a live coding kickoff and press play. 170 00:11:56,740 --> 00:11:58,600 ‫So now I have my debug sphere. 171 00:11:58,600 --> 00:12:05,320 ‫So let's go up to the edge of the world and I'm going to move that mouse cursor up to where it falls 172 00:12:05,320 --> 00:12:07,240 ‫off into the abyss. 173 00:12:07,240 --> 00:12:10,330 ‫And that is where we have the problem. 174 00:12:10,330 --> 00:12:15,940 ‫You see, we don't have a hit result under the cursor when our cursor moves up there because there's 175 00:12:15,940 --> 00:12:18,730 ‫nothing there for us to get a hit result from. 176 00:12:18,730 --> 00:12:22,120 ‫Therefore, our impact point is not defined. 177 00:12:22,120 --> 00:12:25,570 ‫So what we need is something for that line trace to hit. 178 00:12:25,600 --> 00:12:28,810 ‫Now, Unreal Engine has lots of tools that we can use. 179 00:12:28,810 --> 00:12:35,170 ‫What I'm going to do is click the dropdown up here and open my place actor's panel and select this icon 180 00:12:35,170 --> 00:12:38,380 ‫that says volumes and get a blocking volume. 181 00:12:38,380 --> 00:12:39,820 ‫Here's blocking volume. 182 00:12:39,820 --> 00:12:41,710 ‫I'm going to drag one right on in. 183 00:12:41,740 --> 00:12:44,020 ‫So now I have this blocking volume. 184 00:12:44,110 --> 00:12:48,190 ‫Now by default, blocking volumes are supposed to be invisible. 185 00:12:48,190 --> 00:12:54,130 ‫If I go to the details panel for this and scroll down to collision, I see that it's Collision Presets 186 00:12:54,130 --> 00:13:00,940 ‫is Invisible Wall, which seems to suggest that it should block almost everything. 187 00:13:00,940 --> 00:13:06,610 ‫The only thing it's not blocking is the visibility channel and our line trace happens to be tracing 188 00:13:06,610 --> 00:13:08,680 ‫against the visibility channel. 189 00:13:08,680 --> 00:13:13,630 ‫Anything in our world that blocks the visibility channel will be hit by our line trace. 190 00:13:13,630 --> 00:13:16,540 ‫But this particular volume will not. 191 00:13:16,540 --> 00:13:17,860 ‫It's supposed to be invisible. 192 00:13:17,860 --> 00:13:22,690 ‫Well, we can go to the collision presets, open the dropdown and select custom. 193 00:13:22,720 --> 00:13:28,300 ‫This will allow us to change that so I can set the collision response to the visibility channel. 194 00:13:28,300 --> 00:13:29,170 ‫It's a block. 195 00:13:29,170 --> 00:13:34,960 ‫So now I have an invisible volume, but it's set to block the visibility channel, which means line 196 00:13:34,960 --> 00:13:40,180 ‫traces that trace against the visibility channel like ours are going to hit it. 197 00:13:40,180 --> 00:13:45,580 ‫So what I can do is I can take this blocking volume and scale it up. 198 00:13:45,580 --> 00:13:47,800 ‫I'll set it just beyond the wall. 199 00:13:47,800 --> 00:13:53,440 ‫In fact, I can place it right here at the bounds of the wall, and I'll bring it down a bit so that 200 00:13:53,440 --> 00:13:55,900 ‫it's sort of overlapping with the wall. 201 00:13:55,900 --> 00:14:01,930 ‫And that way we have this invisible barrier here, and I'm going to go ahead and scale it up in the 202 00:14:01,930 --> 00:14:03,550 ‫Y direction as well. 203 00:14:03,550 --> 00:14:09,880 ‫So I'll get that nice and big and position it in the middle here and give it a little bit of padding. 204 00:14:09,880 --> 00:14:14,050 ‫And I'm also going to scale it up in the Z direction. 205 00:14:14,050 --> 00:14:18,460 ‫So now it's nice and big and our line trace should hit it. 206 00:14:18,460 --> 00:14:20,080 ‫So let's test that theory. 207 00:14:20,110 --> 00:14:23,170 ‫Let's click in the viewport and go up to the wall. 208 00:14:23,170 --> 00:14:30,250 ‫And sure enough, I am hitting that blocking volume with my line trace and I don't have that issue where 209 00:14:30,250 --> 00:14:34,240 ‫my turret snaps to look at some undefined location. 210 00:14:34,240 --> 00:14:40,810 ‫It's probably looking towards the origin of the world because that impact point vector is all zeros. 211 00:14:40,810 --> 00:14:43,660 ‫Now if I go up to this wall, I have the same issue. 212 00:14:43,660 --> 00:14:46,270 ‫So we need these blocking volumes. 213 00:14:46,600 --> 00:14:48,950 ‫All around the perimeter of our level. 214 00:14:48,970 --> 00:14:50,590 ‫Now, that can be pretty easy. 215 00:14:50,590 --> 00:14:54,820 ‫All I need to do is duplicate this blocking volume. 216 00:14:54,820 --> 00:14:59,290 ‫Now I can change from perspective view to top orthographic view. 217 00:14:59,290 --> 00:15:06,070 ‫So I'm going to select top and scroll out with my mouse wheel and simply hold alt and duplicate this 218 00:15:06,070 --> 00:15:11,620 ‫wall and place one over here and I can hit E to go into rotate mode. 219 00:15:11,620 --> 00:15:14,740 ‫So I'm going to hold alt and rotate by 90 degrees. 220 00:15:14,740 --> 00:15:21,010 ‫That will give me a copy and then I'll hit double u and get my translation mode going and I'll move 221 00:15:21,010 --> 00:15:26,920 ‫it up here to this side and hold Alt and drag a copy down to that side. 222 00:15:26,920 --> 00:15:28,720 ‫So now we have four walls. 223 00:15:28,720 --> 00:15:34,990 ‫Now I can go from top view back to perspective and press play, and now I can go up to any of these 224 00:15:34,990 --> 00:15:40,240 ‫walls and it doesn't matter which wall I'm covered, so that looks great. 225 00:15:40,240 --> 00:15:42,340 ‫So that takes care of one of our problems. 226 00:15:42,340 --> 00:15:43,720 ‫But what about this other one? 227 00:15:43,720 --> 00:15:49,360 ‫If we move the mouse around close to our tank, we still have this sporadic behavior. 228 00:15:49,360 --> 00:15:51,880 ‫So I'd like to take care of that as well. 229 00:15:51,880 --> 00:15:56,770 ‫Now, the way I can take care of this is by interpolating that rotation. 230 00:15:56,770 --> 00:16:02,650 ‫So instead of setting this rotation value directly, we can use an interpolation function which will 231 00:16:02,650 --> 00:16:08,740 ‫essentially move that rotation towards the target that we provide in a smooth manner. 232 00:16:08,740 --> 00:16:10,270 ‫So let's see how that works. 233 00:16:10,270 --> 00:16:15,970 ‫Now, I'd like this interpolation to be in our rotate turret function so we can go back to base pawn 234 00:16:15,970 --> 00:16:22,750 ‫down to rotate turret, and instead of setting our world rotation for the turret to look at rotation, 235 00:16:22,750 --> 00:16:28,240 ‫we can set it equal to the value returned by an interpolation function. 236 00:16:28,240 --> 00:16:34,720 ‫So I'm going to delete, look at rotation and instead we are going to call a function on the F math 237 00:16:34,720 --> 00:16:38,590 ‫library called R inter two. 238 00:16:39,100 --> 00:16:44,530 ‫Now our in two is designed to handle interpolation for rotators. 239 00:16:44,530 --> 00:16:49,720 ‫Now its first input parameter is a const F rotator reference called current. 240 00:16:49,720 --> 00:16:53,650 ‫That's the current value of the thing that we're trying to change. 241 00:16:53,650 --> 00:16:59,560 ‫The thing we're trying to change is our turrets rotation and we can get that from our turret mesh. 242 00:16:59,560 --> 00:17:05,920 ‫So we'll say turret mesh and the function we want to use is get component rotation. 243 00:17:05,920 --> 00:17:10,420 ‫So it's a lot like get component location only it's getting the rotation. 244 00:17:10,420 --> 00:17:14,200 ‫Now the next input is an F rotator called Target. 245 00:17:14,200 --> 00:17:15,310 ‫That's the value. 246 00:17:15,310 --> 00:17:21,430 ‫We want this turret mesh rotation to interpret to to smoothly approach. 247 00:17:21,430 --> 00:17:23,890 ‫That's going to be our look at rotation. 248 00:17:23,890 --> 00:17:26,620 ‫So I'm going to say look at rotation. 249 00:17:26,620 --> 00:17:28,630 ‫The next input is Delta time. 250 00:17:28,630 --> 00:17:30,640 ‫So we know the importance of Delta time. 251 00:17:30,640 --> 00:17:37,030 ‫If we're moving things or rotating things, we want that movement to be independent of the frame rate. 252 00:17:37,030 --> 00:17:39,700 ‫So for that, we can get Delta time. 253 00:17:39,700 --> 00:17:46,210 ‫I can simply include gameplay statics and if you have a good memory, you'll remember that the include 254 00:17:46,210 --> 00:17:49,150 ‫is kismet slash gameplay statics. 255 00:17:49,150 --> 00:17:57,700 ‫So I'll get gameplay statics in here so I can access the static function, get world delta seconds and 256 00:17:57,700 --> 00:18:01,150 ‫remember this requires a world context object. 257 00:18:01,150 --> 00:18:04,030 ‫So I'm going to pass this into that. 258 00:18:04,030 --> 00:18:06,340 ‫And last, we need an internal speed. 259 00:18:06,340 --> 00:18:12,280 ‫The higher the value of internal speed, the faster we will interpolate towards the target. 260 00:18:12,280 --> 00:18:18,550 ‫So if I set this to a value of say, five F, then we'll interpolate fairly slowly. 261 00:18:18,580 --> 00:18:20,470 ‫Let's see how this looks now. 262 00:18:20,470 --> 00:18:25,030 ‫All of this is on a single line and it runs off the screen. 263 00:18:25,030 --> 00:18:32,440 ‫So what I'm going to do is place the input to set world rotation on its own line like this. 264 00:18:32,440 --> 00:18:34,060 ‫So just like that. 265 00:18:34,060 --> 00:18:39,820 ‫And then our interpreter, who has these four input parameters also running off the screen. 266 00:18:39,820 --> 00:18:43,270 ‫So I'm going to set them each on their own lines. 267 00:18:43,270 --> 00:18:49,420 ‫That way we can see all the inputs without having to scroll off the screen like that. 268 00:18:49,420 --> 00:18:49,840 ‫All right. 269 00:18:49,840 --> 00:18:54,220 ‫I'm going to go ahead and save that and kick off live coding. 270 00:18:54,220 --> 00:19:01,150 ‫And now if I press play and I move the mouse, notice that it's taking a while for that rotation to 271 00:19:01,150 --> 00:19:01,480 ‫happen. 272 00:19:01,480 --> 00:19:06,430 ‫That's because we're smoothly interpolating towards that target rotation. 273 00:19:06,430 --> 00:19:07,780 ‫Now, this is great. 274 00:19:07,780 --> 00:19:09,340 ‫That's exactly what I wanted. 275 00:19:09,340 --> 00:19:14,950 ‫No matter how I move my mouse, I'm never going to get that snappy jerky, sporadic movement. 276 00:19:15,040 --> 00:19:20,170 ‫Now, five is an awfully slow Internet speed, but we can change that. 277 00:19:20,170 --> 00:19:21,820 ‫We can make it a little bit faster. 278 00:19:21,820 --> 00:19:28,420 ‫I'm going to set this to 25, see how that looks, and I'll let you go ahead and decide on the value 279 00:19:28,420 --> 00:19:30,040 ‫that you like for your game. 280 00:19:30,040 --> 00:19:34,450 ‫So one more time, kicking off live coding and pressing play. 281 00:19:34,510 --> 00:19:39,010 ‫Now I have a pretty fast interpolation, but it's not snapping. 282 00:19:39,010 --> 00:19:42,910 ‫It's still quick, but it's not an instantaneous snap. 283 00:19:42,910 --> 00:19:46,360 ‫So as long as we're not doing something like this, well, we won't get that. 284 00:19:46,540 --> 00:19:47,860 ‫Crazy behavior. 285 00:19:47,860 --> 00:19:53,500 ‫And of course, if you want a slower rotation, you know how to do it now and we're done with draw debug 286 00:19:53,500 --> 00:19:56,220 ‫sphere, so I'll go ahead and remove that. 287 00:19:56,230 --> 00:19:56,650 ‫Okay. 288 00:19:56,650 --> 00:20:02,920 ‫So in summary, we've set the turret rotation and we're passing in a look at Target, which is an F 289 00:20:02,920 --> 00:20:05,800 ‫vector corresponding to a point in the world. 290 00:20:05,800 --> 00:20:08,080 ‫Right now we're just using the trace hit result. 291 00:20:08,110 --> 00:20:13,090 ‫Now we put this function in the base pong class and made it protected, which means that we were able 292 00:20:13,090 --> 00:20:15,880 ‫to inherit the function in the tank class. 293 00:20:15,880 --> 00:20:21,190 ‫And once we're ready to create a tower class based on base --, then that tower class is going to 294 00:20:21,190 --> 00:20:24,610 ‫inherit this rotate turret function and we can reuse it. 295 00:20:24,610 --> 00:20:26,050 ‫All we need to do is pass. 296 00:20:26,050 --> 00:20:31,750 ‫In a new look at Target, we'll work on creating a tower class derived from base -- in the lectures 297 00:20:31,750 --> 00:20:32,380 ‫to come. 298 00:20:32,380 --> 00:20:33,250 ‫I'll see you soon.