1 00:00:00,840 --> 00:00:03,380 OC Let's dive into robotics simulation. 2 00:00:03,390 --> 00:00:06,720 The tool which we will use for this is called Ignition Gazebo. 3 00:00:06,750 --> 00:00:11,940 For those of you who have used ROS1 or RA Foxy, you probably have utilized Gazebo before. 4 00:00:12,180 --> 00:00:16,980 Well, it is in the process of rebranding and integrating with Ignition robotics. 5 00:00:19,360 --> 00:00:24,740 Now, the interesting thing for you as a developer is the usage of this simulation with Ros. 6 00:00:24,760 --> 00:00:29,020 Well, before we get to that, let's have a look at the ignition command line interface. 7 00:00:31,010 --> 00:00:35,810 In order to install the simulator, We'll go ahead and open up a terminal and run the following command. 8 00:00:43,100 --> 00:00:50,540 So here we are installing the Ross ignition package and this Ross distro flag will just resolve to humble. 9 00:00:50,540 --> 00:00:57,230 So let's be Ross Dash humble dash Ross dash IG and here's the ignition gazebo package. 10 00:00:58,070 --> 00:00:59,510 Go ahead and put in your password. 11 00:01:00,530 --> 00:01:02,720 And for most of you, this will take about 5 minutes install. 12 00:01:02,720 --> 00:01:04,130 So feel free to pause this video. 13 00:01:04,160 --> 00:01:07,370 I have gone ahead and installed this beforehand so I can just continue on with the lecture. 14 00:01:07,370 --> 00:01:10,070 But feel free to pause here while you wait for your installation. 15 00:01:10,760 --> 00:01:15,890 You can find a common example tutorial showcasing ignition gazebo at the following page. 16 00:01:16,100 --> 00:01:21,650 So here it has a test world which you can run called Visualize Light R, which will open up this little 17 00:01:21,650 --> 00:01:26,460 world here with a small robot and a play structure environment. 18 00:01:26,480 --> 00:01:28,130 So I'll go ahead and put this on the side. 19 00:01:29,900 --> 00:01:33,920 So that we can copy the commands and paste them into terminal. 20 00:01:36,710 --> 00:01:39,090 So this opens up the gazebo simulation. 21 00:01:39,110 --> 00:01:44,510 I'll go ahead and full screen this and it opens it up just as we saw it in the tutorial page. 22 00:01:44,510 --> 00:01:48,310 So you can use your middle mouse button to rotate around the screen. 23 00:01:48,320 --> 00:01:55,970 You can use your left mouse button to pan and you can use the right mouse button to zoom in and out. 24 00:01:57,030 --> 00:01:59,400 You can also use your scroll wheel to zoom in and out. 25 00:01:59,910 --> 00:02:04,740 If you're using the virtual machine like VMware, there have been reported issues of the render not 26 00:02:04,740 --> 00:02:05,790 properly displaying. 27 00:02:05,790 --> 00:02:11,610 And one of the ways to fix this issue is to use an older version of the rendering engine like so. 28 00:02:13,950 --> 00:02:16,860 So here we see a playground area with a robot that has a lighter on it. 29 00:02:16,860 --> 00:02:22,830 For those of you who don't know, a lighter is a type of sensor which can detect range using near-infrared 30 00:02:22,830 --> 00:02:26,730 light, usually returning a point cloud of nearby objects. 31 00:02:26,760 --> 00:02:31,440 Now we'll get into how to make a simulation like this in a bit, but let's get a feel for it first. 32 00:02:31,500 --> 00:02:35,810 The top right, we see information about visualizing the leader, which is specific to this example. 33 00:02:35,820 --> 00:02:37,650 Usually you wouldn't see this by default. 34 00:02:38,130 --> 00:02:42,600 In the middle section, we see information about the simulation world, so we can see different things 35 00:02:42,600 --> 00:02:47,670 such as the physics and even magnetic fields associated with this simulation. 36 00:02:48,830 --> 00:02:55,570 And below that we have our entity tree, which has the individual components which are within this simulation. 37 00:02:55,580 --> 00:02:57,710 We can even open this dropdown. 38 00:02:57,710 --> 00:03:02,180 And here in the right we can see how the simulation is performing in real time. 39 00:03:02,180 --> 00:03:05,810 So depending on your computer specs and load, this number may fluctuate. 40 00:03:05,810 --> 00:03:12,500 And lastly, in the lower left, we can pause the simulation and even select the step size of time, 41 00:03:12,500 --> 00:03:14,990 which we want to go forward in. 42 00:03:15,640 --> 00:03:20,450 Now, the interesting thing for you as a ROS developer is the usage of the simulation with Ros. 43 00:03:20,470 --> 00:03:25,450 Well, before we get to that, we have to look at the ignition command line interface with the terminal 44 00:03:25,450 --> 00:03:26,200 open again. 45 00:03:26,650 --> 00:03:28,060 I'll open a new terminal tab. 46 00:03:29,710 --> 00:03:31,700 Again, don't worry about all the messages you may see there. 47 00:03:31,720 --> 00:03:34,420 These are just general messages when running the simulation. 48 00:03:34,420 --> 00:03:41,500 But now in this terminal tab, I can do ignition topic L And here ignition is shorthanded as I g. 49 00:03:41,500 --> 00:03:42,010 N. 50 00:03:44,980 --> 00:03:45,280 All right. 51 00:03:45,280 --> 00:03:49,930 And here we see a series of topics, just like as if we would, if we ran across two topic lists and 52 00:03:49,930 --> 00:03:53,590 had these corresponding topics running on our Ross system. 53 00:03:54,460 --> 00:03:58,630 However, none of these topics are actually connected to Ros, which we could check by running the raw 54 00:03:58,810 --> 00:03:59,770 topic list command. 55 00:04:02,300 --> 00:04:06,920 So here we see none of these corresponding topics are linked to Ros. 56 00:04:07,160 --> 00:04:12,110 That's because any ignition topics we are interested in using in Ross, we need to bridge over which 57 00:04:12,110 --> 00:04:14,130 we can do with the ignition bridge driver. 58 00:04:14,150 --> 00:04:15,950 So let's go ahead and install it. 59 00:04:21,250 --> 00:04:26,050 So if we actually go back to the tutorial page, we can actually scroll down. 60 00:04:28,230 --> 00:04:32,220 And this actually talks about installing the Ross Ignition Bridge like we just mentioned. 61 00:04:32,640 --> 00:04:34,830 And if I scroll down a little bit further. 62 00:04:38,220 --> 00:04:42,400 Can go over to this section talking about visualizing light our data in ROS two. 63 00:04:42,420 --> 00:04:48,330 So here you'll be using the Ros gazebo bridge ROS package, the perimeter bridge node, and then we're 64 00:04:48,330 --> 00:04:56,610 going to be mapping the light sensor message from ignition to a laser scan object in ROS. 65 00:04:56,760 --> 00:05:00,780 So again, if I do the ignition topic L command. 66 00:05:02,000 --> 00:05:05,600 We can see this light hour to topic right here. 67 00:05:07,720 --> 00:05:12,310 And here there are simply specifying the message type, which they are translating it to. 68 00:05:12,340 --> 00:05:15,100 So we're translating it to a sensor message. 69 00:05:15,100 --> 00:05:16,990 Laser scan topic. 70 00:05:17,710 --> 00:05:22,870 And here we specify the ignition message type, which is being transferred from. 71 00:05:23,050 --> 00:05:28,420 So just like Ros topic types, these ignition topics have their own message types, which we are now 72 00:05:28,420 --> 00:05:32,600 bridging over to a topic called laser scan in ROS two. 73 00:05:32,620 --> 00:05:36,040 So let's go ahead and copy this command and try it out for ourselves. 74 00:05:42,030 --> 00:05:42,330 All right. 75 00:05:42,330 --> 00:05:43,890 So let's go on ahead and started running. 76 00:05:43,890 --> 00:05:54,000 And now if we run across two topic list, we can now see we have access to a laser scan topic, which 77 00:05:54,000 --> 00:05:55,710 I can go ahead and echo if I wanted to. 78 00:05:59,520 --> 00:06:01,810 Now notice nothing is being published to. 79 00:06:01,830 --> 00:06:04,770 Well, that's because in the simulation background I paused it. 80 00:06:04,770 --> 00:06:10,380 So if I go ahead and hit play and return back to my terminal, we get a sensor feed being outputted 81 00:06:10,380 --> 00:06:11,870 to our messages. 82 00:06:11,880 --> 00:06:13,500 So I'll go ahead and stop this. 83 00:06:14,070 --> 00:06:19,080 Going back to the tutorial page, it talks a little bit about how you can set up your service instance 84 00:06:19,080 --> 00:06:24,240 to visualize this laser scan information within the Aave's visualizer. 85 00:06:24,240 --> 00:06:25,680 So go ahead and feel free to do that. 86 00:06:25,680 --> 00:06:27,690 But we already talked a little bit about our views. 87 00:06:27,690 --> 00:06:33,420 So for now, let's just go ahead and move on to some of the other features that Ignition Bridge has 88 00:06:33,420 --> 00:06:34,220 to offer. 89 00:06:34,230 --> 00:06:37,650 So for now, I'm going to go ahead and stop this bridge node from running. 90 00:06:40,420 --> 00:06:41,290 Go and clear the screen. 91 00:06:41,290 --> 00:06:45,850 And with that, we should see that our laser scan topic is no longer being published to. 92 00:06:48,020 --> 00:06:53,600 And I can go ahead and stop this simulation from running simply by hitting control C in the terminal, 93 00:06:53,600 --> 00:06:54,680 which it was running in. 94 00:06:55,820 --> 00:06:57,290 And don't worry if it says Ubuntu has a problem. 95 00:06:57,290 --> 00:07:00,410 Sometimes it says that when you close out of the simulation. 96 00:07:00,440 --> 00:07:04,100 Now let's try a different example such as the camera sensor example. 97 00:07:12,330 --> 00:07:13,320 So this might take a while. 98 00:07:13,330 --> 00:07:17,100 As you can see, the download in the background, it's downloading some of the resources. 99 00:07:17,100 --> 00:07:22,230 So if you have a slow internet connection, just keep that in mind that if your simulation takes a while 100 00:07:22,230 --> 00:07:24,090 to install that, that may be the reason. 101 00:07:31,440 --> 00:07:31,740 All right. 102 00:07:31,740 --> 00:07:34,170 So here we see a bunch of random shapes. 103 00:07:34,170 --> 00:07:35,580 So we see this little cone object. 104 00:07:35,580 --> 00:07:44,070 Here we see this oops, we see this cube object, we see a sphere and we see a little black cube. 105 00:07:44,310 --> 00:07:47,160 So this little black box represents a camera. 106 00:07:47,160 --> 00:07:53,130 So we can use this camera window here in the right to view the camera topic from within the ignition 107 00:07:53,130 --> 00:07:53,700 ecosystem. 108 00:07:53,700 --> 00:07:57,930 So if I hit the refresh button, it'll refresh the available topics that I can subscribe to. 109 00:07:57,930 --> 00:08:05,580 And here we see the cube and the cone and the ball, which are currently sitting within this simulation 110 00:08:05,580 --> 00:08:06,390 we have here. 111 00:08:06,630 --> 00:08:11,670 Or alternatively, we can use the parameter bridge to again view this in Ross. 112 00:08:11,670 --> 00:08:15,300 So again, if I do ignition topic L. 113 00:08:20,600 --> 00:08:23,840 We can see we have this camera topic being published, too. 114 00:08:24,110 --> 00:08:29,600 So if we go back to our old parameter bridge command, all we have to do is change some of these parameters 115 00:08:29,600 --> 00:08:31,430 a bit to match what we're looking for. 116 00:08:31,430 --> 00:08:36,350 So instead of the light hour two topic, we are trying to bridge the camera topic and instead of the 117 00:08:36,350 --> 00:08:43,010 laser scan message type from sensor messages, we are going to be changing this to a image message type. 118 00:08:45,820 --> 00:08:51,580 And instead of this being a laser scan instance in ignition, it's called an image as well. 119 00:08:53,640 --> 00:08:59,670 Then we're passing in some Ross arcs, which all we're doing is mapping the default topic name, which 120 00:08:59,670 --> 00:09:03,330 in this case it will get transferred to the same type of topic name. 121 00:09:03,330 --> 00:09:04,350 So camera. 122 00:09:05,860 --> 00:09:11,590 And we can set it to something else which may match the Rasta ecosystem a bit better, which may be 123 00:09:11,590 --> 00:09:15,760 something along the lines of camera slash image raw. 124 00:09:16,690 --> 00:09:17,380 All right. 125 00:09:17,380 --> 00:09:20,590 And now if I go ahead and do raw topic list. 126 00:09:22,720 --> 00:09:25,960 We have our image raw instance and if I echo it. 127 00:09:29,460 --> 00:09:34,740 We see the pixel information being displayed to the screen and of course we could do something like 128 00:09:34,740 --> 00:09:38,790 our go to visualizations image view. 129 00:09:41,600 --> 00:09:44,680 Can refresh the topics and select the camera image raw. 130 00:09:44,690 --> 00:09:50,690 We see that same image feed we were seeing in the ignition ecosystem, but now we're able to utilize 131 00:09:50,690 --> 00:09:52,100 it within Ross. 132 00:09:52,170 --> 00:09:53,300 I'll go ahead and close this. 133 00:09:55,390 --> 00:09:55,660 All right. 134 00:09:55,660 --> 00:10:01,630 So that should give you a gist of the workflow and ROS integration of this ignition gazebo simulation. 135 00:10:01,660 --> 00:10:06,670 You can find the PDF files that come with the ignition gazebo installation at the following location. 136 00:10:16,980 --> 00:10:22,490 So here we see a series of PSD files with different examples that you can run. 137 00:10:22,500 --> 00:10:27,810 For example, let's try and look at the camera sensor as a file we have here running in the background. 138 00:10:35,210 --> 00:10:41,930 So here in VW's code, we can simply see that this PDF file follows an XML syntax to it, and it has 139 00:10:41,930 --> 00:10:47,570 several things such as a world attribute, physics attributes and a series of plug ins. 140 00:10:50,240 --> 00:10:54,890 Instances which we are rendering the 3D scene and more plugins. 141 00:10:55,160 --> 00:10:56,900 And if we scroll down further. 142 00:10:57,640 --> 00:11:02,890 We can see there are models such as this box model, which is that red cube we saw earlier. 143 00:11:04,630 --> 00:11:09,430 We see a sphere model which has different geometry attributes to it. 144 00:11:10,280 --> 00:11:16,970 And we see our camera model, which in this case has just a simple box geometry to it. 145 00:11:17,780 --> 00:11:25,010 But it also has this sensor tag to it, which links to the sensor plugin, which gives it attributes 146 00:11:25,010 --> 00:11:32,180 such as the width and height of the image as well as the frame rate and field of view and even the topic 147 00:11:32,180 --> 00:11:32,480 name. 148 00:11:32,510 --> 00:11:37,520 Now, one of the biggest issues I have with this new user interface with Ignition Gazebo is that it 149 00:11:37,520 --> 00:11:42,620 does not have a built in model editor to help automatically generate these PSD files. 150 00:11:42,620 --> 00:11:46,850 So this can be a pain when you have to generate your own PSD files and then continuously run it to see 151 00:11:46,850 --> 00:11:48,250 what it looks like in the simulation. 152 00:11:48,260 --> 00:11:54,010 So for now, let's try to create our own SDF world file to run in ignition gazebo. 153 00:11:54,020 --> 00:11:59,270 So I'll go ahead and set up our package to hold the files we are going to be creating in folders called 154 00:11:59,270 --> 00:12:01,130 Worlds and Models. 155 00:12:01,880 --> 00:12:05,510 And if I go ahead and open up a new file Explorer window and take a look at this. 156 00:12:08,000 --> 00:12:12,740 We can see we have these new world and models folders which are empty. 157 00:12:13,650 --> 00:12:18,840 So within Vsco, I can create a new world file, which I'll just call Test World. 158 00:12:20,780 --> 00:12:25,580 First thing I will do is set my language syntax in the bottom right to XML. 159 00:12:26,210 --> 00:12:29,470 And if you ever want to, you can always set this as the default setting. 160 00:12:29,480 --> 00:12:35,930 You can always configure the file association for SDA to always be XML and this way VTS code will remember 161 00:12:35,930 --> 00:12:36,290 it. 162 00:12:36,320 --> 00:12:41,750 Now there's actually some handy functionality in this code for HTML files, which look very similar 163 00:12:41,750 --> 00:12:45,890 to XML in which it will auto close tags for us when we create them. 164 00:12:45,890 --> 00:12:49,850 So for the time being I will configure SDF files to be treated as HTML. 165 00:12:51,570 --> 00:12:54,870 You can always just do this manually for each file like so. 166 00:12:57,250 --> 00:13:01,180 And now we see the icon has changed to simulate the HTML five logo. 167 00:13:01,180 --> 00:13:04,360 And for now, I'll go ahead and set my tab size to two. 168 00:13:05,720 --> 00:13:13,010 So first things first, I'm going to put in a Steph and world tag and I will set Steph version to 1.7 169 00:13:13,010 --> 00:13:15,050 and call my World Test World. 170 00:13:20,230 --> 00:13:25,390 One of the easiest ways to get up and running is to include existing models, which we can find on the 171 00:13:25,390 --> 00:13:26,920 Ignition Models page. 172 00:13:30,940 --> 00:13:35,440 So if you ever want to look into easily exportable models for your simulation, you can check them out 173 00:13:35,440 --> 00:13:35,890 here. 174 00:13:35,920 --> 00:13:41,570 For now, I will include a sun instance to light our scene and a ground plane from open robotics. 175 00:13:41,590 --> 00:13:44,620 You can always search these up within the models instance here. 176 00:13:45,370 --> 00:13:50,860 So if I search up sun, we see the one from open robotics here and we can see here, we can easily copy 177 00:13:50,860 --> 00:13:53,650 the SDF snippet to our clipboard. 178 00:13:56,050 --> 00:13:57,700 And include it in our world. 179 00:14:00,250 --> 00:14:07,270 So here we've created our include tags and then specified a URI, which in this case is the location 180 00:14:07,270 --> 00:14:09,040 of this particular model. 181 00:14:10,530 --> 00:14:14,160 We'll go back to the instance and I will search for a ground plane. 182 00:14:19,190 --> 00:14:24,800 And I will just choose this simple gray one from open robotics and we'll do the same exact thing. 183 00:14:27,660 --> 00:14:30,210 With that, I can go ahead and save the file. 184 00:14:31,930 --> 00:14:37,600 Go into our terminal and I'll stop the current simulation that's running and the parameter bridge. 185 00:14:40,320 --> 00:14:45,180 Go ahead and make some extra space for now and we'll change into the directory where our world file 186 00:14:45,180 --> 00:14:46,020 is located. 187 00:14:46,650 --> 00:14:51,780 So here we can see our test world PSD file and we can run it just like we did with the other files with 188 00:14:51,860 --> 00:14:56,400 Iron Gazebo and the name of the world, which is Test World SDF. 189 00:14:58,080 --> 00:15:00,990 Oh, and I forgot to set the version to 1.7. 190 00:15:06,590 --> 00:15:07,940 Let's go ahead and save that. 191 00:15:08,150 --> 00:15:09,140 Let's try this again. 192 00:15:12,910 --> 00:15:14,060 And there we go. 193 00:15:14,080 --> 00:15:21,610 So here we see nothing special, just a blank world with a sun and ground plain object, which is this 194 00:15:21,610 --> 00:15:23,990 gray square we see here. 195 00:15:24,010 --> 00:15:26,440 Now, this doesn't really teach you much on how to make your own models. 196 00:15:26,440 --> 00:15:29,020 So let's create a model within our world file. 197 00:15:29,170 --> 00:15:34,140 Let's start with something simple, like making our own ground plane that we can customize. 198 00:15:34,150 --> 00:15:40,210 So I'll go ahead and comment out the ground plane, include statement by hitting control and forward 199 00:15:40,210 --> 00:15:45,280 slash, which will do this format for doing a multi line comment. 200 00:15:45,280 --> 00:15:50,320 And let's go ahead and create our own ground plane, which we start off with a model tag. 201 00:15:52,540 --> 00:15:55,150 The model will contain attributes and links. 202 00:15:55,150 --> 00:16:00,490 For example, one attribute we will want to set is called static to True, which will fix this object 203 00:16:00,490 --> 00:16:02,620 in the simulation so it doesn't move. 204 00:16:04,440 --> 00:16:06,720 Now let's go ahead and create a link for our model. 205 00:16:13,420 --> 00:16:17,680 Now, in order for our ground plane to be visible in our simulation, we will need to create visual 206 00:16:17,680 --> 00:16:19,240 attributes within our link. 207 00:16:22,320 --> 00:16:24,960 Then I need to give this a geometry attribute. 208 00:16:25,050 --> 00:16:29,160 In which case I want this to be a plane so I can format it like so. 209 00:16:33,270 --> 00:16:36,190 Now I need to pass in attributes for this form. 210 00:16:36,210 --> 00:16:39,360 You will have different attributes depending on which geometry you chose. 211 00:16:39,360 --> 00:16:43,650 But in the case of the plane, I need to specify a normal, which is the direction the top part of the 212 00:16:43,650 --> 00:16:44,540 plane points. 213 00:16:44,550 --> 00:16:51,120 So in our case, I want the plane to be flat on the XY plane and I will specify the Z section as one, 214 00:16:51,420 --> 00:16:56,280 then specify the size attribute which takes in the length and width, and I'll just set it to 25 by 215 00:16:56,280 --> 00:16:57,540 25 metres. 216 00:16:59,770 --> 00:17:00,240 Great. 217 00:17:00,250 --> 00:17:05,110 Now let's set a material attribute outside of the geometry tag, but still within the visual tag. 218 00:17:05,690 --> 00:17:11,900 Then there are three attributes to specify which are ambient, diffuse and specular, which reference 219 00:17:11,900 --> 00:17:15,500 different ways which light can interact or emit from our model. 220 00:17:15,710 --> 00:17:19,520 Each of these can take in a red, green, blue and alpha value. 221 00:17:19,520 --> 00:17:24,920 So to set it to blue and not be transparent, I will set the last two numbers to be one. 222 00:17:27,260 --> 00:17:31,070 And we can copy this between the diffuse and specular attribute names. 223 00:17:37,460 --> 00:17:41,600 So I'll simply alt click to get multiple cursors and I can change the name like so. 224 00:17:44,180 --> 00:17:45,090 All right, that's it. 225 00:17:45,110 --> 00:17:51,010 We created a new model called ground plane set static to true, so it doesn't move within the simulation. 226 00:17:51,020 --> 00:17:56,510 And then we created a link which has a visual geometry of plane where we specify the size and material 227 00:17:56,510 --> 00:17:57,380 properties. 228 00:17:57,380 --> 00:18:01,190 Let's save this file and rerun the simulation in our terminal. 229 00:18:04,440 --> 00:18:07,350 So go ahead and clear the screen and rerun it. 230 00:18:09,710 --> 00:18:16,040 So notice this looks very similar, except now we have a blue plane since we've changed the color attributes 231 00:18:16,040 --> 00:18:18,830 within our SDF file here. 232 00:18:20,900 --> 00:18:23,150 And if you went ahead and clicked on this model. 233 00:18:25,150 --> 00:18:30,820 We can select the visual attribute of this particular ground link, go down to material, and we can 234 00:18:30,820 --> 00:18:35,200 see here it is specifying the colors that we specified within the code editor. 235 00:18:35,860 --> 00:18:39,100 And if you wanted to, you could go ahead and change the colors. 236 00:18:40,570 --> 00:18:44,400 I'll go ahead and see what it looks like when I change all of those different types of ways light can 237 00:18:44,400 --> 00:18:46,080 bounce off to orange. 238 00:18:46,110 --> 00:18:50,640 Now, there's something I want to show you in which I can add a cube to the simulation by clicking on 239 00:18:50,640 --> 00:18:54,720 this box in the upper left corner and placing it down. 240 00:18:55,080 --> 00:19:00,030 And I'll actually go ahead and click on it, translate it, and I'll put it slightly above. 241 00:19:02,370 --> 00:19:06,210 And I'll put it slightly above our ground plane. 242 00:19:08,750 --> 00:19:14,660 Now if I hit play to start the simulation, notice it falls straight through our ground plane and begins 243 00:19:14,660 --> 00:19:18,440 falling down below so we can see it falling very far away. 244 00:19:18,860 --> 00:19:20,840 Now, that's hardly useful for us, right? 245 00:19:20,840 --> 00:19:25,640 So we see this plane here, but it's not actually interacting with any of our physical objects. 246 00:19:25,670 --> 00:19:27,910 Let's go ahead and pause this for now so the cube stops falling. 247 00:19:27,920 --> 00:19:31,400 So in order to prevent this, we have to create collision tags. 248 00:19:31,670 --> 00:19:33,440 So let's go ahead and add that now. 249 00:19:33,620 --> 00:19:39,410 So outside of the visual scope of our model, I will create our collision tags and call this a collision 250 00:19:39,410 --> 00:19:39,980 ground. 251 00:19:43,420 --> 00:19:48,400 Then within the tags I will copy the same geometry attributes I have in my visual model. 252 00:19:51,810 --> 00:19:52,110 All right. 253 00:19:52,110 --> 00:19:57,810 So it's just a plane with a size of 25 by 25 and the Z normal pointing upwards. 254 00:19:58,870 --> 00:20:04,240 Now, the reason we have to repeat this is because you can have different visuals from your collision. 255 00:20:04,270 --> 00:20:09,700 Sometimes people will create complex meshes to make their simulation models look highly realistic, 256 00:20:09,700 --> 00:20:15,910 but want to keep the collision geometry simple so that the physics engine does not have to try to calculate 257 00:20:15,910 --> 00:20:20,440 physics for complex shapes with different components and densities. 258 00:20:21,730 --> 00:20:27,460 But with that done, let's save the file and go ahead and rerun our simulation. 259 00:20:32,700 --> 00:20:35,070 All right, So we see our blue plane again. 260 00:20:37,560 --> 00:20:38,730 Put our cube down. 261 00:20:41,750 --> 00:20:43,190 Raise it up above our plane. 262 00:20:43,190 --> 00:20:48,960 And this time if I hit play, it doesn't go falling through the plane like it did earlier. 263 00:20:48,980 --> 00:20:53,840 It's also worth noting you can interact with attributes of the simulation itself, such as gravity. 264 00:20:54,410 --> 00:21:01,160 So in this case I can set gravity to be positive 0.5 meters per second squared in the Z direction. 265 00:21:02,310 --> 00:21:05,220 So saving that and restarting our world. 266 00:21:09,920 --> 00:21:16,820 So now if I place the cube down, hit play, we see the cube begins to float above the plane upwards 267 00:21:16,820 --> 00:21:19,100 because we made gravity positive. 268 00:21:19,100 --> 00:21:25,540 In this instance, instead of the -9.8 meters per second squared we're used to in real life. 269 00:21:25,700 --> 00:21:30,200 Now I'll go back to our code and comment that out so that our simulations don't behave like that in 270 00:21:30,200 --> 00:21:30,860 the future. 271 00:21:30,860 --> 00:21:33,920 But keep it here so that you know, you can interact with it if you need it. 272 00:21:34,460 --> 00:21:39,110 Now, you can probably imagine that if we keep adding all these model tags and all their attributes 273 00:21:39,110 --> 00:21:44,930 within our world file, that this file will begin to get really crowded and we may end up editing attributes 274 00:21:44,930 --> 00:21:46,160 from the wrong model. 275 00:21:46,250 --> 00:21:52,670 So let's go ahead and separate our model into a separate file so we can simply include it into our world 276 00:21:52,670 --> 00:21:53,330 instead. 277 00:21:54,800 --> 00:21:59,300 I can do this by creating a new folder in our models folder called Ground Plane. 278 00:21:59,300 --> 00:22:03,200 Then within this new folder, create a file called Model SDF. 279 00:22:03,710 --> 00:22:09,770 We'll start this file off with some SDF tag and then in between the tags we can paste in the contents 280 00:22:09,770 --> 00:22:12,370 of our model from our test world. 281 00:22:12,380 --> 00:22:18,560 So I'll go ahead and comment this out from our test world file and place them into our model that SDF 282 00:22:18,560 --> 00:22:20,750 file that we created here in the ground plane folder. 283 00:22:20,750 --> 00:22:24,970 With that done, we now have to create a model config file within that same folder. 284 00:22:24,980 --> 00:22:28,010 So I'll click new file model config. 285 00:22:29,700 --> 00:22:32,940 And I will configure this file as XML. 286 00:22:35,640 --> 00:22:37,920 Oh, and be sure to set this to HTML. 287 00:22:38,460 --> 00:22:39,120 Here we go. 288 00:22:42,380 --> 00:22:47,810 Then I can add a model tag which will contain information about your model's name, version and PSD 289 00:22:47,960 --> 00:22:48,500 file. 290 00:22:59,550 --> 00:23:05,210 Now, the nice thing is by default, you should specify your model as model SDF here in the config file. 291 00:23:05,220 --> 00:23:09,200 But thanks to this config file, you can rename it to something that makes more sense. 292 00:23:09,210 --> 00:23:13,980 That way if you have multiple files open for different models in your code editor, you have a better 293 00:23:13,980 --> 00:23:16,320 idea what each one is that you're editing. 294 00:23:16,320 --> 00:23:23,670 So just to prove that this works, I can change this to say, ground plane, SDF or here, I'll do better, 295 00:23:23,670 --> 00:23:25,410 I'll do my ground plane at SDF. 296 00:23:25,410 --> 00:23:27,420 So don't get confused with the standard ground plane. 297 00:23:28,160 --> 00:23:32,180 And then rename this model that PDF file here to match. 298 00:23:36,200 --> 00:23:36,530 All right. 299 00:23:36,530 --> 00:23:41,210 So here we're specifying the My Ground plan, that PDF file, and we've specified that name as such 300 00:23:41,210 --> 00:23:41,860 right here. 301 00:23:41,870 --> 00:23:46,310 Then last thing to include is information about the model author, as well as a brief description of 302 00:23:46,310 --> 00:23:47,720 what this model is. 303 00:24:05,260 --> 00:24:08,230 Now I can be sure that both these files are saved. 304 00:24:08,980 --> 00:24:11,290 Go into my test file. 305 00:24:13,280 --> 00:24:14,090 And I'll copy over. 306 00:24:14,090 --> 00:24:21,470 This includes statement with the URI strings and the URI, we will instead be specifying will be in 307 00:24:21,470 --> 00:24:25,760 the model's slash ground plane folder. 308 00:24:26,540 --> 00:24:30,920 And just to make this a bit more clean, I'll go ahead and format it like so. 309 00:24:31,040 --> 00:24:36,500 And just to prove that this is using our new ground plane PSD file instead of the one we created directly 310 00:24:36,500 --> 00:24:40,820 within the world file earlier, I can actually go ahead and change up the colors a little bit, so I'll 311 00:24:40,820 --> 00:24:42,140 change this to teal. 312 00:24:43,040 --> 00:24:45,800 And so I'll save the my ground plane PSD file. 313 00:24:46,100 --> 00:24:47,540 So again, this is being included here. 314 00:24:47,540 --> 00:24:51,410 I'm not modifying any of the commented alt model that was here before. 315 00:24:51,440 --> 00:24:56,930 And if I go back to our terminal, stop our test world from running, rerun it. 316 00:24:59,250 --> 00:25:05,130 We see we now have this world with a total ground plane model associated with it. 317 00:25:07,370 --> 00:25:11,090 And we see the source file path is my ground plane dot SDF. 318 00:25:11,120 --> 00:25:16,400 Now, this is great, but keep in mind, the thing I use for the location model won't always work. 319 00:25:16,430 --> 00:25:24,230 For example, if I went a directory back and then tried to rerun these simulation like so. 320 00:25:29,260 --> 00:25:32,590 We get an error message saying unable to find Yuri. 321 00:25:32,620 --> 00:25:37,450 That's because the path is relative to the current working directory, not the world file. 322 00:25:37,660 --> 00:25:42,280 The way we can resolve this is by instead setting an environment variable to point to the resource path 323 00:25:42,280 --> 00:25:43,420 for our simulation. 324 00:25:43,750 --> 00:25:49,750 In this case it is our model's directory, which I can get by printing the current directory and then 325 00:25:49,750 --> 00:25:52,210 setting the environment variable like so. 326 00:25:59,830 --> 00:26:02,110 Then I can go into the PDF file. 327 00:26:03,000 --> 00:26:04,710 And delete the folder name. 328 00:26:05,220 --> 00:26:07,320 So I'll go ahead and save this. 329 00:26:08,930 --> 00:26:10,280 Rerun our simulation. 330 00:26:13,890 --> 00:26:18,600 And here now, even though we're in a different directory, the simulation loads just fine because it's 331 00:26:18,600 --> 00:26:24,090 able to load in the resource path since we set the particular environment variable. 332 00:26:25,510 --> 00:26:25,900 All right. 333 00:26:25,900 --> 00:26:27,880 This is a good place to stop this lecture. 334 00:26:27,880 --> 00:26:33,340 So far, we've learned some basics about the ignition gazebo simulator, as well as how we can create 335 00:26:33,340 --> 00:26:36,070 PSD files for the simulator to process. 336 00:26:36,310 --> 00:26:41,800 We created a simple ground plane model which we learned how to include within our SDA file so that we 337 00:26:41,800 --> 00:26:45,340 can keep all the code related to our models separate from our world file. 338 00:26:45,610 --> 00:26:51,460 We also ran through the intro tutorial of an example simulation of a robot on a playground that used 339 00:26:51,460 --> 00:26:57,940 a LIDAR sensor, and so how Ignition Gazebo has its own ecosystem of commands and topics which we can 340 00:26:57,970 --> 00:26:59,860 then bridge into ROS. 341 00:26:59,860 --> 00:27:05,380 So in the next lecture we'll be taking a closer look at how we can implement sensors and plug ins into 342 00:27:05,380 --> 00:27:10,210 our SDF files to make them much more useful for us as robotics developers.