WEBVTT 00:00.850 --> 00:04.180 Welcome to the introduction to blender physics. 00:04.240 --> 00:05.860 So why use physics. 00:05.860 --> 00:11.620 Well it simulates the real world we live in a physical world where things fall over they bounce off 00:11.620 --> 00:17.570 of one another and we can use the physics engine in blender to simulate this. 00:17.570 --> 00:23.080 Now you can manually place every bit of destroyed or deformed geometry if you wanted to. 00:23.080 --> 00:28.730 And that's what this section is focussed on is the destruction and defamation of geometry. 00:28.760 --> 00:32.610 However you can also use the physics engine to animator with. 00:32.770 --> 00:39.040 So instead of animating a ball rolling down a surface or bouncing off of something you could use the 00:39.040 --> 00:41.830 physics engine to do that for you. 00:41.830 --> 00:48.850 Now it does enable you to create complex scenes easily and quickly so you can go down the route manually 00:48.870 --> 00:51.400 placing things and having that exact control. 00:51.460 --> 00:59.230 But if you were trying to simulate a wall falling over or perhaps some glass shattering you probably 00:59.230 --> 01:05.510 don't want to do that manually because it would be an absolute pain to do so. 01:05.620 --> 01:11.020 But if you fancy a challenge you can go half and through that I'm not going to because this is great 01:11.020 --> 01:11.820 for realism. 01:11.830 --> 01:16.360 As I've mentioned shattering glass falling towers you can even make some dominoes or something along 01:16.360 --> 01:18.400 those lines with it. 01:18.400 --> 01:23.670 Of course those things are quite complex so we're going to start with something simple. 01:23.750 --> 01:29.950 We're going to focus initially on rigid body physics what's rigid body physics will as the name suggests 01:30.220 --> 01:34.700 it simulates the physics of rigid or solid bodies. 01:34.720 --> 01:44.170 So if you imagine just hard surfaces said chairs tables glasses etc. they all come under that solid 01:44.170 --> 01:45.040 body. 01:45.430 --> 01:51.220 Now this works very closely with the animation system as I've been alluding to it. 01:51.340 --> 01:57.040 You can simulate a ball rolling down a hill or two objects bouncing off of one another and it works 01:57.100 --> 02:00.130 in conjunction with the animation system rather seamlessly. 02:00.130 --> 02:05.930 Some of the other physics simulations don't work so well with the animation system. 02:07.090 --> 02:10.370 Now it's all move and rotate objects. 02:10.390 --> 02:15.910 That's important so it was going to translate them and rotate them as they fall through the air or as 02:15.910 --> 02:17.590 they break apart. 02:17.590 --> 02:20.300 Now what it won't do is deform them. 02:20.800 --> 02:23.370 Okay so now we've got that under our belts. 02:23.470 --> 02:27.990 Let's go play with rigid body physics and hop on over in a blender. 02:28.870 --> 02:32.360 Okay so over in blender and I'm going to do a couple of things. 02:32.380 --> 02:35.200 I'm going to just save a default layout. 02:35.200 --> 02:39.390 I'm going to keep it almost like the fault lay out when you first open blender. 02:39.390 --> 02:44.110 However I'm going to set the end frame at 50 for the moment. 02:44.110 --> 02:48.310 I've got a feeling I'm going to set this up several times so I'm literally going to save the starter 02:48.310 --> 02:49.950 file as it is there. 02:50.000 --> 02:50.850 Perfect. 02:50.890 --> 02:54.490 So don't open up the tool shelf here and select my cube. 02:54.490 --> 03:01.150 Now there are a couple of ways of adding a rigid body physics to a any mesh object in blender. 03:01.150 --> 03:07.630 So there is a physics tab it's quite hard to redev when it's all squished up but it's just there and 03:07.630 --> 03:08.560 want something selected. 03:08.560 --> 03:11.990 We have two options to add active and add passive. 03:12.160 --> 03:15.800 Now you can also do that on the properties window itself. 03:15.820 --> 03:21.970 There's a little bouncy ball icon and we've got rigid body and when you click that's there. 03:21.970 --> 03:24.820 By default you'll get an active object. 03:24.820 --> 03:25.690 Now what does that do. 03:25.690 --> 03:29.460 Well let's go ahead and press play now or use a shortcut. 03:29.530 --> 03:29.840 Oh. 03:29.880 --> 03:32.590 In a way we can see that it falls away. 03:32.680 --> 03:38.370 And 50 frames seems to be a good loop point because it's disappeared from the screen. 03:38.370 --> 03:45.700 Now if this was active it means that it is being controlled by the physics engine. 03:45.700 --> 03:50.720 If it's passive It means it's not but will still interact with other Richard bodies. 03:53.500 --> 03:57.500 So if we set this now to passive we can see it just sits there. 03:57.640 --> 04:00.130 However if we put another cube into the scene. 04:00.130 --> 04:00.930 Well let's do that. 04:00.940 --> 04:02.940 Let's and Jube jubilate This cube. 04:02.950 --> 04:05.370 And I'm just going to move up on the. 04:06.490 --> 04:13.590 Z axis there and then move it across just a little on the X and make that want active. 04:13.810 --> 04:15.420 Okay let's see what happens. 04:15.430 --> 04:18.550 There we go it falls off into oblivion. 04:18.730 --> 04:23.200 So that's quite useful and in fact here I'm looking a set that a little longer since now it's falling 04:23.200 --> 04:24.630 for longer. 04:24.640 --> 04:25.470 There we go. 04:25.600 --> 04:31.310 So with 75 frames there we seem to get quite a fall animation we can see it disappearing. 04:31.630 --> 04:33.580 So what are the other options. 04:33.580 --> 04:38.020 Because in general it's great to just hit add active or add passive. 04:38.020 --> 04:41.520 But in general we're going to want to have a bit more detail. 04:41.710 --> 04:46.350 So over in the properties panel itself we've got some options now. 04:46.420 --> 04:53.840 Active and passive are here animated is very useful because it enables us to use the animation system 04:53.870 --> 04:59.190 a key the movements in and then let's blend of physics take over later on. 04:59.290 --> 05:04.060 We won't do that at the moment but we can do that later on the mass. 05:04.060 --> 05:09.390 Now the mass itself is pretty self-explanatory it's the weight of our object. 05:09.400 --> 05:17.160 Now this is in kilograms and that is a was that's a two by two metre cube essentially weighing one kilograms 05:17.160 --> 05:21.610 so it's going to act like a 1 kilogram two meter cube. 05:21.610 --> 05:28.720 However if that weighed 10 kilos it would act slightly differently as you can see it's not sort of bouncing 05:28.720 --> 05:30.650 off as far as it would do before. 05:30.760 --> 05:37.330 And if we set that as a very lights one we can see it behaves differently as well so we can change the 05:37.330 --> 05:39.010 mass of our objects. 05:39.010 --> 05:44.750 Now one thing to bear in mind is if you haven't set the scale correctly. 05:44.770 --> 05:49.100 So let's bring out the properties window here. 05:49.180 --> 05:54.270 So we've got a scale here of 1 1 1 and on here of 1 1 1 which is absolutely fine. 05:54.280 --> 05:58.830 However if we scale something up an unfit flies there. 05:59.140 --> 06:04.210 If we scale something up like that we we see that it's going to act slightly differently. 06:04.210 --> 06:09.940 In fact in this case because we scaled it and moved it whilst the physics engine was running it's not 06:09.940 --> 06:12.550 like that at all so let's just put it slightly above. 06:12.790 --> 06:20.410 So this is going to act differently because it's bigger but it will still act as if it was a smaller 06:20.410 --> 06:21.400 cube. 06:21.400 --> 06:28.630 So what we'd need to do in this case is make sure we apply with control a or go into object and apply 06:28.750 --> 06:38.050 the actual scale and then it should be hafe like an appropriately sized cube that weighs 10 kilos that 06:38.050 --> 06:44.950 can be very odd to get your head round at first but it does mean that the physics will act more realistically. 06:44.950 --> 06:51.010 Of course if the desired result you want is a little bit unrealistic then you can do that so that's 06:51.010 --> 06:52.950 absolutely fine. 06:52.990 --> 06:58.840 Now rigid body collisions the next area down we've got a convex hull and the meshes self. 06:58.840 --> 07:04.960 In general I wouldn't bother picking any of the others for the moment because it does change how things 07:04.960 --> 07:05.750 behave. 07:05.770 --> 07:10.240 So if I selected sphere this will act more like a ball. 07:10.270 --> 07:16.000 And as you can see let's zoom in here so we can see it is actually intersecting and that's because instead 07:16.000 --> 07:23.290 of using the outside faces of our mesh as basically where it's bumping into it's put a sphere inside 07:23.290 --> 07:24.050 our model. 07:24.050 --> 07:29.410 Now there may be reasons why you want that so either no to make a cube roll. 07:29.440 --> 07:35.260 But so if we were doing that we could go down to the next area and go to collision margin put that on 07:35.680 --> 07:36.910 and then increase it. 07:36.910 --> 07:42.000 Now we set that top one and see what happens it will work. 07:42.070 --> 07:44.380 It hasn't seemed to do much in this case. 07:44.380 --> 07:46.200 I'm guessing it's still going inside the model. 07:46.330 --> 07:53.410 Let's send it back to Convex Hull and let the simulation run and we can see there's a one blend the 07:53.410 --> 07:54.670 unique gap. 07:54.940 --> 07:57.690 It's literally hitting it a blender unit away. 07:58.620 --> 08:00.120 So this can be useful. 08:00.120 --> 08:01.780 I would not set it to zero. 08:01.860 --> 08:09.300 But if you're having objects passing through one another the small small at that it was at before the 08:09.300 --> 08:14.460 point 0 4 is usually more than enough to prevent it passing through. 08:14.460 --> 08:20.520 Now friction is as we can gather is that how friction is the surface of that is. 08:20.520 --> 08:25.800 So it was set down to zero it would have no friction and freely scoots across a lot of surfaces. 08:25.890 --> 08:31.980 And if it was one it would really grip onto any surface it comes into contact with bounciness of course 08:32.040 --> 08:35.110 is how bouncy an object is. 08:35.120 --> 08:40.710 And we might not see in this particular simulation perhaps a ball bouncing on the ground would be a 08:40.710 --> 08:46.710 better object bearer example of something as bouncy or indeed something that's got zero friction and 08:46.710 --> 08:47.520 high bouncing us. 08:47.520 --> 08:47.910 There we go. 08:47.910 --> 08:52.460 We can see that was skipping over the surface really quickly and bouncing away. 08:53.120 --> 08:53.540 Brilliant. 08:53.570 --> 08:54.190 Okay. 08:54.260 --> 08:59.520 So there's rigid body dynamics down here at the moment we won't go into that just at the moment. 08:59.660 --> 09:06.380 But you can literally deactivate something until something else comes into contact with it. 09:06.380 --> 09:11.400 If you wanted to and well since we're here let's do it anyway dampening. 09:11.480 --> 09:18.230 Well we can dampen its movement or its rotation so we can say here that it's resistant to rotation. 09:18.230 --> 09:21.920 Then when it hits Oh that is just really odd. 09:21.920 --> 09:23.030 Was that what we intended. 09:23.030 --> 09:25.810 Well maybe not let's turn it down a little. 09:25.850 --> 09:31.520 So something is irritating a little too quickly after it's hit we can dampen that rotation and translation 09:31.520 --> 09:32.990 is exactly the same. 09:33.100 --> 09:40.800 At one you can see that well it's kind of like it's falling through goo rather than falling free. 09:40.890 --> 09:43.160 Is she not getting through. 09:43.160 --> 09:49.460 But if we lower that we can make the whole thing just a little bit more controlled rather than bouncing 09:49.460 --> 09:50.440 all over the place. 09:50.570 --> 09:56.870 So you can play with these to your heart's content of course to get some an effect or a simulation that 09:56.870 --> 09:57.880 you desire. 09:58.710 --> 10:01.840 And of course that is up to a challenge. 10:02.220 --> 10:06.690 I would like you to go ahead and create a short physics simulation. 10:06.690 --> 10:14.700 So create a simple scene using basic meshes gennari a physics simulation with some interactions so things 10:14.700 --> 10:21.110 are hitting one and over and use both passive and active rigid bodies. 10:21.880 --> 10:24.220 Pause video now and give That's a go. 10:26.930 --> 10:28.080 Okay guys welcome back. 10:28.100 --> 10:31.090 Let's go create a short physics simulation. 10:33.550 --> 10:39.780 Okay so I've started off in a default scene here and I'm going to really icky but I don't want a cube. 10:39.790 --> 10:41.220 I want a plane. 10:41.230 --> 10:43.330 I'm going to scale up the plane. 10:43.570 --> 10:48.370 Not pushing it through itself too about that and I'm going to tilt it so slightly down here so I'm going 10:48.370 --> 10:52.050 to rotate on the x direction and then just do that. 10:52.060 --> 10:55.390 So whatever lands on here should then slide down. 10:55.390 --> 11:00.990 So let's go ahead and add something to land on it's going to add in a U.S. sphere and then we use it 11:00.990 --> 11:05.610 as a ball and pop it in here and just see what happens. 11:05.620 --> 11:10.090 Now of course we've not applied any physics yet so what do we need we need on here. 11:10.090 --> 11:13.690 This is going to stay still so we need to add a rigid bullet to both of these. 11:13.840 --> 11:18.110 And of course if we decide to play at the moment they both fall away. 11:18.340 --> 11:22.820 So what I'm ONLY to do is make the ground itself passive. 11:23.170 --> 11:26.500 And then the ball should hit the ground and roll. 11:26.950 --> 11:27.660 Excellent. 11:27.670 --> 11:33.830 Now looks like in this case we're going to need slightly more frame someone to go up to 200 here. 11:33.850 --> 11:35.800 That should give us plenty to see what happens. 11:35.800 --> 11:37.670 It should accelerate down here. 11:38.390 --> 11:39.230 Perfect. 11:39.260 --> 11:39.860 Okay. 11:39.960 --> 11:44.560 So now that we've done that let's play with some of the settings and see what happens. 11:44.570 --> 11:52.370 So both of these have a friction point five which is resistance to moving and about in this syrup. 11:52.370 --> 11:56.290 So what happens if we set the ground with a bounciness of 1. 11:56.420 --> 12:00.510 Extremes are a great way of testing things doesn't do anything. 12:00.530 --> 12:04.720 Okay so what happens if we set both of them to a bounciness of 1. 12:05.590 --> 12:07.540 I'm guessing it's going to bounce x. 12:07.570 --> 12:11.000 So there we go there's a bouncing ball going down the hill. 12:11.770 --> 12:13.260 Let's set this to zero. 12:13.270 --> 12:15.640 And I'm guessing it won't bounce. 12:15.760 --> 12:21.220 Okay so this is a great example of experimentation and working out the bounciness. 12:21.250 --> 12:26.800 If both of one or more of the items have anything with zero in them especially the floor if you've got 12:26.800 --> 12:30.190 more than one item then it's not going to really work. 12:30.190 --> 12:38.140 However what this could both do for us is if we go back to the BE IN of the animation and let's say 12:38.310 --> 12:45.760 let's go from a top few here and let's duplicate this a couple of times before it hit the right key. 12:45.760 --> 12:47.220 So there we go. 12:50.010 --> 12:51.130 So you got plenty there. 12:51.210 --> 12:57.540 Now if they impact one out of it because they of course they won't impact each other down a straight 12:57.540 --> 12:58.440 slope like that. 12:58.450 --> 13:00.780 They'll just race one another into oblivion. 13:00.840 --> 13:07.470 Bought we can do here is well let's subdivide our plane and give it some substance really under we go 13:07.470 --> 13:12.780 for a simple subdivision and I'm going to apply that subdivision Locanda in edit mode. 13:12.780 --> 13:13.420 There we go. 13:13.650 --> 13:15.640 So now we've got something to play with. 13:15.660 --> 13:21.930 I can pull up some geometry for it to for them to bounce off of. 13:22.380 --> 13:26.760 Because they won't bounce off of it till we're actually in object mode. 13:28.570 --> 13:34.420 Okay so we're letting them roll down and we can see that the bullet Oh things are falling through the 13:34.420 --> 13:35.070 floor. 13:36.240 --> 13:37.540 Let's just let it settle. 13:37.740 --> 13:40.320 Let's redo the animation. 13:41.660 --> 13:43.670 Well I wasn't expecting that. 13:43.740 --> 13:46.490 I'm going to add modify and add. 13:47.470 --> 13:51.940 A subdivision is surfacing just to smooth those out ever so slightly. 13:54.100 --> 13:56.070 Let's see if that's made any difference. 13:56.100 --> 14:00.650 Okay so these balls are now passing through the surface of our model. 14:00.750 --> 14:07.890 Now that would suggest that it's not having time to calculate the impact that these balls are having 14:07.900 --> 14:10.270 or literally they're passing through the surface. 14:10.290 --> 14:16.650 I'll make sure that's let's say the mesh itself rather than a convex whole let's see if that makes a 14:16.650 --> 14:17.100 difference. 14:17.100 --> 14:18.580 This resets and plate. 14:18.590 --> 14:20.240 Yes it does make a difference. 14:20.280 --> 14:23.800 Now will these balls collide with one another kind of. 14:23.820 --> 14:25.400 But they're not bouncing off of one of. 14:25.410 --> 14:31.580 So let's give the ground a bit of bounciness and the balls will maybe be a bit more interesting. 14:34.320 --> 14:40.290 And again this is one of these things that you can play with to your heart's content until you get it 14:40.560 --> 14:42.170 how you want it to be. 14:42.180 --> 14:48.150 Now the margin here might help if he probably does now that these aren't falling through. 14:48.150 --> 14:50.180 That's one of the differences here. 14:50.220 --> 14:55.760 The convects hole the coalition margin if it's not there allows them to fall through. 14:56.010 --> 15:01.320 So I see examples of that actually work in action so we can move it's convex whole and we can see they're 15:01.320 --> 15:05.500 hitting one another and they have got a bounciness of one. 15:05.730 --> 15:10.740 Let's give them let's make them frictionless or make this one frictionless and see what happens. 15:10.980 --> 15:14.520 So that's just sliding and pushing the other one down. 15:14.930 --> 15:21.030 So because it's got no friction it's not rotating so we can add in a tiny bit of friction because that 15:21.300 --> 15:23.280 ruins are a physics model. 15:23.280 --> 15:28.620 So we've got to start from the beginning again and that's because some friction it should grip. 15:28.620 --> 15:30.940 There we go and rotates. 15:30.990 --> 15:33.450 I don't think I've got enough things that for it to bump into. 15:33.450 --> 15:39.900 But by now you should have got the gist of your marble run or whatever you guys have created and do 15:39.900 --> 15:43.740 remember to show your work in the discussions over the forum. 15:43.740 --> 15:48.310 Love to see what you guys come up with some simple physics in blender. 15:48.630 --> 15:52.120 And as always I will see you guys in the next lecture.