WEBVTT 00:04.340 --> 00:08.620 Hello everybody and welcome to this reminder video it's been a while since we've had one of these. 00:08.720 --> 00:14.420 Now when it comes to applying a transforms and physics it is incredibly important if we don't apply 00:14.420 --> 00:19.910 our transforms to the physics engine will think something is smaller or larger or weighs more or less 00:19.910 --> 00:22.190 than it should do compared to its volume. 00:22.190 --> 00:25.520 So you end up adjusting the density of something without even realizing. 00:25.640 --> 00:30.010 And obviously if you're trying to mimic brakes as we're going to do in this section then you're going 00:30.010 --> 00:33.620 to end up with something not acting as you would expect it to. 00:33.770 --> 00:35.430 So that is really important. 00:35.450 --> 00:39.230 So let's learn a bit more about applying transforms and how they're going to affect you in physics by 00:39.230 --> 00:41.640 hopping straight on over in a blender. 00:42.580 --> 00:46.150 Okay so we're back over in blender and we have two things in front of us. 00:46.150 --> 00:52.500 We've got three balls on each of these ramps these ramps are slightly downwards as you can see here 00:52.510 --> 00:54.150 they do have a slope to them. 00:54.200 --> 00:58.020 I've already set out the physics and will learn a lot more about that at the moment. 00:58.030 --> 01:01.710 We just need to focus on what happens if we don't apply it transforms. 01:01.720 --> 01:07.410 So the three balls on the left here and the ramp are a duplicate of these three balls on the right. 01:07.420 --> 01:11.410 The only difference is they they always the same. 01:11.620 --> 01:14.410 They all have the same friction and all the other set ups. 01:14.470 --> 01:17.740 But the difference between these two the one on the left. 01:17.740 --> 01:20.390 All of these have a scale factor of one. 01:20.410 --> 01:23.490 Now these ones on the right have a slightly different scale factor rubbering. 01:23.500 --> 01:24.990 Open the properties tab. 01:25.120 --> 01:29.480 If I select the one on the right here we can see it's got a scale of point one. 01:29.560 --> 01:35.200 This has a scale of one in the middle and then the one on the left has a scale of 10. 01:35.230 --> 01:39.550 So they will behave slightly differently depending on what they are. 01:39.550 --> 01:45.190 So in reality the one on the far left of this group of three is much smaller. 01:45.370 --> 01:49.010 And on the right is much larger by a factor of 10 both ways. 01:49.120 --> 01:54.890 So let's without any further do let's go ahead now and play the animation and see what happens. 01:55.760 --> 02:00.980 So the balls dropped down a little bit of a bounce to them and we see and there will be some randomness 02:00.980 --> 02:03.210 here that's just part of the physics engine itself. 02:03.230 --> 02:08.920 But we see that these three balls are pretty much going at the same speed down this ramp. 02:09.170 --> 02:13.050 And the smallest ball is going quicker than the medium ball. 02:13.070 --> 02:15.480 And then this one's barely moving it. 02:15.500 --> 02:16.860 I mean it is moving. 02:17.050 --> 02:19.020 You know they dropped off the end there. 02:19.190 --> 02:25.210 So this one here is slowly moving down but it's not behaving as you would expect it to. 02:25.370 --> 02:27.940 And this is something that will throw you a lot. 02:27.950 --> 02:34.280 When it comes to your animations especially if you're using the physics engine in it if you've not applied 02:34.280 --> 02:36.910 the scale it's not going to act as you would expect it to. 02:36.920 --> 02:41.360 And that could be obviously very annoying if you then go and tweak loader parameters and then realize 02:41.510 --> 02:45.360 I only had remembered to apply my scale. 02:45.530 --> 02:47.160 Now there are a couple of other things. 02:47.190 --> 02:53.450 Sometimes if you inadvertently apply the wrong location you can get some really weird results as well. 02:53.630 --> 02:57.640 And we had that warning in right back if you remember when we were doing the Skittles. 02:57.650 --> 03:02.840 If you've got the centre of mass or the origin of the object in the wrong place you'll end up doing 03:02.840 --> 03:04.790 weird things as well. 03:04.790 --> 03:10.170 In this case the origin of all of these objects of course is in the middle of them so we stop it here 03:10.760 --> 03:18.020 and let's go back to the normal default view that we'd have and we've got the origins right smack bang 03:18.020 --> 03:21.260 in the middle of each of these balls which is where it should be. 03:21.260 --> 03:22.900 That's where the centre of masses. 03:23.060 --> 03:29.480 If we decided to have a bit of fun of course and move that centre of mass slightly to one edge that's 03:29.580 --> 03:33.780 the centre of mass on top of this ball solona left click on the very top of the ball. 03:33.810 --> 03:35.060 I've run out of zoom. 03:35.130 --> 03:40.940 This happens so often you select it so we can zoom right in and put 3-d cursor on the top and in the 03:40.940 --> 03:47.690 tool shelf itself under the Tools Options set the origin to the 3D cursor. 03:47.690 --> 03:52.220 So now all of the mass of this ball is distributed on the very top. 03:52.340 --> 03:57.020 And I'm going to do the same on this one but this time on its side and then we're just going to laugh 03:57.060 --> 04:02.990 as it ends up Mexican being down the entire ramp this origins of 3-d cursor. 04:02.990 --> 04:07.760 So let's see what happens if we go ahead and do that because we've moved where the masses and we can 04:07.760 --> 04:12.890 see that these things are moving in a very weird way in fact I don't think the slope is big enough. 04:12.910 --> 04:15.860 But they're tending to go towards where that weight is. 04:15.860 --> 04:20.840 Perhaps I've been a bit too extreme on that mascara's distribution but there we go. 04:20.840 --> 04:30.620 So in this case this would be a case of in here going apply the location and then see what happens after 04:30.620 --> 04:31.610 that. 04:33.100 --> 04:34.120 Oh it's gone really weird. 04:34.120 --> 04:35.550 Now look at it go. 04:36.010 --> 04:41.560 I wonder how those amazing So if we go ahead and inadvertently have plied the location that's move the 04:41.560 --> 04:43.250 origin all the way over here. 04:43.270 --> 04:45.460 I've seen that happen so many times. 04:45.460 --> 04:50.650 So the origin is well back in the whole origin of the entire world at zero zero zero. 04:50.770 --> 04:55.990 The ball of course is nowhere near that so often in these cases if you've inadvertently done that's 04:56.020 --> 05:02.320 very easy to do you can go to set origin after the object is selected and move it to the centre of mass 05:02.350 --> 05:05.100 either by the surface or in this case of unadilla volume. 05:05.110 --> 05:10.600 And I can do the same here with this next one set origin to the centre of mass and we'll learn a lot 05:10.600 --> 05:12.230 more about that in the next lecture. 05:12.250 --> 05:15.860 But let's just make sure these are now going down as we would expect them to. 05:17.030 --> 05:18.190 Yes they are working. 05:18.200 --> 05:20.250 And let's just fix these here so we. 05:20.300 --> 05:26.360 If I select this one here and apply the scale and on the end apply the scale as well. 05:26.360 --> 05:30.110 Now we should see that they behave very much like each other. 05:30.110 --> 05:35.330 Of course there will be some randomness but we can see they're all falling at an appropriate rate for 05:35.330 --> 05:42.620 what they're doing and they should all reach the end pretty much together give or take a few frames 05:42.620 --> 05:43.280 difference. 05:43.280 --> 05:44.000 Perfect. 05:44.060 --> 05:49.430 So I hope that's clear that things and specifically why you need to apply your transforms when it comes 05:49.430 --> 05:50.620 to doing physics. 05:50.890 --> 05:53.570 And I will see you all in that next lecture.