1 00:00:04,300 --> 00:00:05,260 ‫Hello and welcome. 2 00:00:05,260 --> 00:00:12,010 ‫This lecture, we're going to be enabling physics simulation within our scene so that we can get cubes 3 00:00:12,010 --> 00:00:16,240 ‫to move around and things to float as if they were in zero g. 4 00:00:16,270 --> 00:00:18,580 ‫Let's dive in and see how this works. 5 00:00:18,910 --> 00:00:24,400 ‫So this game is going to be one of physics interaction with objects bumping into each other and creating 6 00:00:24,400 --> 00:00:25,900 ‫mess and chaos. 7 00:00:26,110 --> 00:00:30,490 ‫Let's have a look at how we can do this sort of thing in Unreal. 8 00:00:30,610 --> 00:00:34,960 ‫Let's go over to the minimal default level editor tab. 9 00:00:35,680 --> 00:00:42,280 ‫And what we're going to do is by default, none of these objects will actually be affected by physical 10 00:00:42,280 --> 00:00:42,700 ‫laws. 11 00:00:42,700 --> 00:00:50,560 ‫So if I take this chair and select it and bring it up in the air and then I go ahead and hit play, 12 00:00:50,560 --> 00:00:53,770 ‫it just hangs there as if gravity was not a thing. 13 00:00:53,920 --> 00:01:00,550 ‫The reason for this is that it is expensive for your CPU to simulate physics, so if it doesn't have 14 00:01:00,550 --> 00:01:05,770 ‫to, unreal will not do it for any object in the scene. 15 00:01:06,280 --> 00:01:09,910 ‫So we need to go ahead and enable it explicitly. 16 00:01:09,910 --> 00:01:17,140 ‫So make sure that the chair is still selected and then let's drag out the details pane so we can see 17 00:01:17,140 --> 00:01:18,220 ‫this a little bit better. 18 00:01:18,520 --> 00:01:21,850 ‫Now at the top of the details pane is a list of things called components. 19 00:01:21,850 --> 00:01:23,230 ‫We don't have to worry about this too much. 20 00:01:23,230 --> 00:01:30,760 ‫Just make sure the topmost item is selected and then below the search bar you can see that there are 21 00:01:30,760 --> 00:01:34,060 ‫properties and below the search bar there's actually a list of filters. 22 00:01:34,060 --> 00:01:38,470 ‫There's general actor, Lod, misc and physics. 23 00:01:38,470 --> 00:01:44,470 ‫I'd like you to select physics so that we're seeing only the actor's properties relating to physics. 24 00:01:45,190 --> 00:01:50,680 ‫And you'll see that there is a checkbox here labeled simulate physics, and it's currently set to false. 25 00:01:50,680 --> 00:01:58,780 ‫If you check that box and hit play, then we get the chair dropping and simulating physics there. 26 00:01:58,810 --> 00:02:02,380 ‫Now we can also do this with objects that we add in. 27 00:02:02,380 --> 00:02:09,220 ‫So I could go to the quickly add button in the toolbar, go to shapes and cube, and drag a cube in 28 00:02:09,220 --> 00:02:10,840 ‫just under the chair. 29 00:02:11,020 --> 00:02:19,510 ‫And in fact, I'm going to bring this above the chair and select simulate physics for that cube. 30 00:02:19,570 --> 00:02:25,480 ‫If I hit play, then you can see the cube lands on top of the chair and they interact with each other 31 00:02:25,480 --> 00:02:28,900 ‫as well as interacting with other objects in the scene. 32 00:02:28,900 --> 00:02:32,830 ‫Now there are a couple of other physical properties worth noting here. 33 00:02:32,830 --> 00:02:36,610 ‫One of them is the Enable Gravity CheckBox. 34 00:02:36,610 --> 00:02:43,360 ‫So if I took this chair and the one with physics enabled and disabled gravity then hit play, you can 35 00:02:43,360 --> 00:02:51,100 ‫see the chair just floats as if there were no gravity, whereas the cube still falls as if it has a 36 00:02:51,100 --> 00:02:52,840 ‫normal amount of gravity. 37 00:02:52,960 --> 00:02:57,190 ‫And then the other property I just want you to take note of is the mass. 38 00:02:57,190 --> 00:03:03,910 ‫This is how much something weighs, essentially how many kilograms of substance there is there by default. 39 00:03:03,910 --> 00:03:10,780 ‫This is calculated for you, but you can check the checkbox there to give it a mass that you want so 40 00:03:10,780 --> 00:03:14,080 ‫you can make something super heavy or super light. 41 00:03:14,080 --> 00:03:21,250 ‫So if I make the chair super heavy, you can see it reacts a lot less to the cube falling onto it and 42 00:03:21,250 --> 00:03:24,400 ‫it moves much more slowly and sluggishly. 43 00:03:24,400 --> 00:03:28,660 ‫So let's challenge you to knock the lamp off the table using the physics system. 44 00:03:28,660 --> 00:03:31,270 ‫So enable physics for both the lamp and the table. 45 00:03:31,270 --> 00:03:37,510 ‫For this to work, place a large object over the table, presumably with gravity enabled, and knock 46 00:03:37,510 --> 00:03:38,140 ‫it over. 47 00:03:38,140 --> 00:03:39,700 ‫Pause the video and have a go. 48 00:03:43,320 --> 00:03:43,860 ‫Okay. 49 00:03:43,870 --> 00:03:44,750 ‫Welcome back. 50 00:03:44,760 --> 00:03:49,710 ‫So I can actually use the cube that I've already got to try and knock this over. 51 00:03:49,740 --> 00:03:53,760 ‫So I'm going to move the chair so that the cube hopefully lands down onto the table. 52 00:03:53,760 --> 00:03:57,390 ‫Then I'm going to select the table and the lamp on it. 53 00:03:57,390 --> 00:04:02,970 ‫I can do that with a shift click to select both and I can change the details of both at the same time 54 00:04:02,970 --> 00:04:08,730 ‫so I can go ahead and enable physics by clicking the simulate physics checkbox and hit play. 55 00:04:08,730 --> 00:04:10,050 ‫Let's see if this works. 56 00:04:10,350 --> 00:04:14,070 ‫It landed on the table, but it didn't quite knock it over. 57 00:04:14,310 --> 00:04:20,220 ‫So I'm going to make that a bit of a heavier cube by selecting the cube and overriding its mass with 58 00:04:20,220 --> 00:04:24,570 ‫the checkbox and setting the mass to 1000 as well. 59 00:04:24,600 --> 00:04:25,740 ‫Let's hit that. 60 00:04:25,740 --> 00:04:32,940 ‫So a heavier mass meant that the the statue just went flying off the table when it was hit. 61 00:04:32,940 --> 00:04:34,290 ‫That's all for this lecture. 62 00:04:34,320 --> 00:04:35,760 ‫I'll see you in the next one.