1 00:00:05,160 --> 00:00:07,640 Hi, welcome to this new video. 2 00:00:07,640 --> 00:00:08,880 We're going to continue working 3 00:00:08,880 --> 00:00:11,210 on our ecosystem simulation. 4 00:00:11,210 --> 00:00:13,340 In this video, we're going to be 5 00:00:13,340 --> 00:00:16,700 continuing on the work on the decision tree. 6 00:00:16,700 --> 00:00:18,980 How we're using a decision tree 7 00:00:18,980 --> 00:00:20,760 in the brain of the herbivore, 8 00:00:20,760 --> 00:00:22,500 which is one of the classes that we have 9 00:00:22,500 --> 00:00:25,445 our animals that will eat food eventually. 10 00:00:25,445 --> 00:00:27,980 We're going to be able 11 00:00:27,980 --> 00:00:29,920 to evaluate or execute some functions like 12 00:00:29,920 --> 00:00:35,975 wander and seek food by navigating the decision tree. 13 00:00:35,975 --> 00:00:37,980 What have we done so far? We created 14 00:00:37,980 --> 00:00:40,780 a decision tree that has an awake state. 15 00:00:40,780 --> 00:00:42,640 Are you awake, condition? 16 00:00:42,640 --> 00:00:44,100 Then it checks, are you hungry or 17 00:00:44,100 --> 00:00:47,650 not and then it dictates if it's going to go into, 18 00:00:47,650 --> 00:00:50,710 seeking food mode or wondering. 19 00:00:50,710 --> 00:00:52,840 We want to associate 20 00:00:52,840 --> 00:00:55,120 a function in the code 21 00:00:55,120 --> 00:00:56,785 that will be executed if we're in that state, 22 00:00:56,785 --> 00:00:58,300 in the final state of wander. 23 00:00:58,300 --> 00:01:01,485 But that function should also have a transition, 24 00:01:01,485 --> 00:01:05,660 meaning that if let's say if we wander for a long time, 25 00:01:05,660 --> 00:01:07,405 maybe we start getting hungry, 26 00:01:07,405 --> 00:01:10,880 or the hunger level starts growing and eventually, 27 00:01:10,880 --> 00:01:12,980 the wander state reaches 28 00:01:12,980 --> 00:01:16,995 a threshold or a point of transition, 29 00:01:16,995 --> 00:01:20,920 in which we are going to reevaluate the decision tree. 30 00:01:20,920 --> 00:01:22,540 Some decision trees would actually 31 00:01:22,540 --> 00:01:25,480 just navigate back to the previous node, 32 00:01:25,480 --> 00:01:27,960 and potentially ask that question again. 33 00:01:27,960 --> 00:01:30,730 Are we going to seek food? 34 00:01:30,730 --> 00:01:32,880 But we want to create a system 35 00:01:32,880 --> 00:01:34,480 that might be able to completely 36 00:01:34,480 --> 00:01:38,130 evaluate the decision tree and double check. 37 00:01:38,130 --> 00:01:40,940 It may be that a condition such as wander or it 38 00:01:40,940 --> 00:01:43,820 might make the entity sleepy, 39 00:01:43,820 --> 00:01:45,580 and we want to go back all the way 40 00:01:45,580 --> 00:01:48,590 down to the question of, are you awake. 41 00:01:48,860 --> 00:01:51,680 We're going to be able to return to the root, 42 00:01:51,680 --> 00:01:53,580 and we're going to do that with our same function 43 00:01:53,580 --> 00:01:54,960 or construct the decision tree. 44 00:01:54,960 --> 00:01:57,260 We're going to refresh the decision tree, 45 00:01:57,260 --> 00:01:58,580 go back to the root node, 46 00:01:58,580 --> 00:02:02,850 and start the cascading down in the flow chart as we go. 47 00:02:02,850 --> 00:02:05,205 Let's see how we can put this in action. 48 00:02:05,205 --> 00:02:08,520 We're going to jump here into processing. 49 00:02:08,520 --> 00:02:12,810 What do we have so far? We just constructed. 50 00:02:12,810 --> 00:02:15,890 I'm continuing with the code that we did last video. 51 00:02:15,890 --> 00:02:18,010 I'm here in the herbivore class, 52 00:02:18,010 --> 00:02:19,345 and we just wrote 53 00:02:19,345 --> 00:02:24,125 the update current node and build a decision tree. 54 00:02:24,125 --> 00:02:26,705 We basically created the nodes, 55 00:02:26,705 --> 00:02:30,240 gave the information for them and 56 00:02:30,240 --> 00:02:34,090 we created the flow chart navigation. 57 00:02:34,850 --> 00:02:38,235 Let's just try to create 58 00:02:38,235 --> 00:02:41,850 because that we end up in some of these action notes. 59 00:02:41,850 --> 00:02:43,120 But right now these action notes, 60 00:02:43,120 --> 00:02:46,280 we are just printing the line, if you remember here. 61 00:02:46,280 --> 00:02:47,740 We're just printing the line. 62 00:02:47,740 --> 00:02:49,390 You're currently in this action note. 63 00:02:49,390 --> 00:02:50,920 It doesn't do anything. 64 00:02:50,920 --> 00:02:52,615 It doesn't execute a function. 65 00:02:52,615 --> 00:02:57,340 We're going to comment out this line. 66 00:02:57,340 --> 00:02:58,900 We're going to try to execute 67 00:02:58,900 --> 00:03:00,360 specific functions that are 68 00:03:00,360 --> 00:03:02,300 associated with the behaviors. 69 00:03:02,300 --> 00:03:03,860 We're not still going to fully 70 00:03:03,860 --> 00:03:05,540 fleshed out those functions, 71 00:03:05,540 --> 00:03:07,545 but let's create functions for them. 72 00:03:07,545 --> 00:03:10,480 Let's define the wander function. 73 00:03:12,530 --> 00:03:14,720 For now, also, we're going to use 74 00:03:14,720 --> 00:03:17,340 the placeholder print line. 75 00:03:20,750 --> 00:03:24,160 I'm wandering. 76 00:03:37,670 --> 00:03:41,700 That's the function wander. 77 00:03:41,700 --> 00:03:53,955 Let's define rest function. 78 00:03:53,955 --> 00:03:56,760 Basically, let's do the same thing. 79 00:03:56,760 --> 00:03:58,775 I hope you understand this. 80 00:03:58,775 --> 00:04:00,240 I'm trying to work on the structure 81 00:04:00,240 --> 00:04:03,035 before I'm actually working on the behavior. 82 00:04:03,035 --> 00:04:08,360 Here, we're going to say I'm resting and then 83 00:04:08,360 --> 00:04:22,285 the function seek food. 84 00:04:22,285 --> 00:04:25,950 We're going to type here, I'm seeking food. 85 00:04:26,740 --> 00:04:29,915 These are the functions that we want to execute, 86 00:04:29,915 --> 00:04:32,840 so how would we go about passing 87 00:04:32,840 --> 00:04:34,505 these functions to the nodes 88 00:04:34,505 --> 00:04:35,825 so that whenever we create a node, 89 00:04:35,825 --> 00:04:38,700 the node knows which function to call? 90 00:04:39,010 --> 00:04:44,405 Let's just delete or comment out this print out. 91 00:04:44,405 --> 00:04:47,750 We want to say the current node 92 00:04:47,750 --> 00:04:49,820 should activate its own function, 93 00:04:49,820 --> 00:04:53,495 so what we could do here is go to the node 94 00:04:53,495 --> 00:04:58,130 and let's do a new thing, 95 00:04:58,130 --> 00:05:01,880 a new piece of information that the node might have, 96 00:05:01,880 --> 00:05:05,270 which we're going to call action function, 97 00:05:05,270 --> 00:05:08,720 abbreviate that a little bit action func. 98 00:05:08,720 --> 00:05:11,270 None. We're creating 99 00:05:11,270 --> 00:05:14,240 a new variable called action function. 100 00:05:14,240 --> 00:05:17,945 Now we can make the internal variable 101 00:05:17,945 --> 00:05:22,685 self.action function equals to action function. 102 00:05:22,685 --> 00:05:24,680 This is something that we haven't seen yet, 103 00:05:24,680 --> 00:05:27,185 which is, this is a variable. 104 00:05:27,185 --> 00:05:31,850 But we could assign a function to a variable. 105 00:05:31,850 --> 00:05:34,985 That's an interesting technique. 106 00:05:34,985 --> 00:05:40,700 Let's just say assign to this action function. 107 00:05:40,700 --> 00:05:43,085 In this area here, 108 00:05:43,085 --> 00:05:45,330 all the action nodes, 109 00:05:45,490 --> 00:05:52,235 we will be able to assign to them a function. 110 00:05:52,235 --> 00:05:56,670 Let's just do in this case, self.wander. 111 00:05:58,420 --> 00:06:01,145 Because we created that function already. 112 00:06:01,145 --> 00:06:02,900 The function is self.wander. 113 00:06:02,900 --> 00:06:04,445 It's written here, 114 00:06:04,445 --> 00:06:06,965 so we're assigning that to this variable. 115 00:06:06,965 --> 00:06:08,435 That means that we can actually 116 00:06:08,435 --> 00:06:11,480 execute that function because 117 00:06:11,480 --> 00:06:13,055 the node would have a variable 118 00:06:13,055 --> 00:06:16,790 that gives us access to that. 119 00:06:16,790 --> 00:06:20,855 Let's just do the next one, 120 00:06:20,855 --> 00:06:26,100 which is the next one would be self.seek food. 121 00:06:32,110 --> 00:06:35,540 We're going to do the same thing for 122 00:06:35,540 --> 00:06:43,535 action function for rest, self.rest. 123 00:06:43,535 --> 00:06:45,620 Because each one of these functions will 124 00:06:45,620 --> 00:06:47,480 be printing these texts, 125 00:06:47,480 --> 00:06:48,740 we need to make sure that 126 00:06:48,740 --> 00:06:50,780 those functions are being executed. 127 00:06:50,780 --> 00:06:52,730 Instead of printing this line 128 00:06:52,730 --> 00:06:53,990 here that was a placeholder, 129 00:06:53,990 --> 00:07:05,490 let's say that the current node ,.action function. 130 00:07:07,210 --> 00:07:09,740 Because that's a function, we're going to just 131 00:07:09,740 --> 00:07:11,510 use open and closed parentheses. 132 00:07:11,510 --> 00:07:13,145 That's not a variable. 133 00:07:13,145 --> 00:07:18,005 It's actually a function that lives within this node. 134 00:07:18,005 --> 00:07:20,525 We can actually call that directly. 135 00:07:20,525 --> 00:07:22,400 Obviously, each one of those would be 136 00:07:22,400 --> 00:07:24,425 different depending on the node we're in, 137 00:07:24,425 --> 00:07:26,090 but now we're actually not only 138 00:07:26,090 --> 00:07:27,845 associating data to a node, 139 00:07:27,845 --> 00:07:30,695 but also potentially a functionality to the node, 140 00:07:30,695 --> 00:07:32,990 like a particular form of execution of 141 00:07:32,990 --> 00:07:36,125 code will happen at the end of this decision tree. 142 00:07:36,125 --> 00:07:38,015 Again, we're not spending time 143 00:07:38,015 --> 00:07:42,395 in diving deeper into what these functions are doing, 144 00:07:42,395 --> 00:07:43,940 which we're going to do in the next few videos. 145 00:07:43,940 --> 00:07:46,250 But we're trying to make sure that our decision tree, 146 00:07:46,250 --> 00:07:47,840 it's not only constructed, 147 00:07:47,840 --> 00:07:50,750 but is capable to executing code. 148 00:07:50,750 --> 00:07:54,710 Let's see if we have this working. 149 00:07:54,710 --> 00:07:56,780 You see right now we have, 150 00:07:56,780 --> 00:07:57,950 I'm seeking food, 151 00:07:57,950 --> 00:08:00,455 so that function is being called. 152 00:08:00,455 --> 00:08:03,380 The function seeking food, I'm seeking food. 153 00:08:03,380 --> 00:08:05,975 That's because if we look at the data, 154 00:08:05,975 --> 00:08:08,255 is hungry is true. 155 00:08:08,255 --> 00:08:10,610 Let's just make it false again. 156 00:08:10,610 --> 00:08:21,005 To see. I'm wondering, 157 00:08:21,005 --> 00:08:22,490 so we are executing those functions. 158 00:08:22,490 --> 00:08:25,520 That's great. Let's look at one example of how we 159 00:08:25,520 --> 00:08:30,050 transition out of let's say we're in wander state, 160 00:08:30,050 --> 00:08:32,720 and that wander execution, 161 00:08:32,720 --> 00:08:37,140 we want to go from wander to hungry. 162 00:08:37,270 --> 00:08:39,620 Well, we're going to need to 163 00:08:39,620 --> 00:08:42,020 create a few extra variables for that. 164 00:08:42,020 --> 00:08:48,700 We're going to use a particular naming convention here. 165 00:08:48,700 --> 00:08:57,220 We're going to say self.hunger level equal zero. 166 00:08:57,220 --> 00:08:58,360 That's going to be something that 167 00:08:58,360 --> 00:09:00,280 counts how hungry are we 168 00:09:00,280 --> 00:09:05,690 and self.hunger threshold, 169 00:09:11,520 --> 00:09:15,390 and we're going to say something like 100. 170 00:09:16,220 --> 00:09:21,420 The threshold would represent how high 171 00:09:21,420 --> 00:09:23,670 this value of the hunger value needs 172 00:09:23,670 --> 00:09:26,625 to get to trigger a transition, 173 00:09:26,625 --> 00:09:29,055 and the level is going to be a country. 174 00:09:29,055 --> 00:09:30,210 We're going to start 0, 1, 2, 175 00:09:30,210 --> 00:09:31,725 3, 4, 5, 6, 7, 176 00:09:31,725 --> 00:09:35,010 until we get to the hungry state 177 00:09:35,010 --> 00:09:36,630 and something will happen. 178 00:09:36,630 --> 00:09:41,580 Let's just It's a very simple counting statement here, 179 00:09:41,580 --> 00:09:46,815 we're going to say if the hunger level. 180 00:09:46,815 --> 00:09:49,050 First of all, we're going to say hunger level 181 00:09:49,050 --> 00:09:50,280 plus equals one, 182 00:09:50,280 --> 00:09:52,020 so every frame we go up in one, 183 00:09:52,020 --> 00:09:53,730 and if the hunger level it's bigger 184 00:09:53,730 --> 00:09:58,120 than the hunger threshold. 185 00:10:05,210 --> 00:10:08,700 Basically, this is the moment in which we transition. 186 00:10:08,700 --> 00:10:17,130 What we want to transition is a self.hunger equals true. 187 00:10:17,130 --> 00:10:21,765 We're saying that this state of, 188 00:10:21,765 --> 00:10:24,880 actually is called is hungry. 189 00:10:28,820 --> 00:10:32,595 Which is our bullion. Let's just double check. 190 00:10:32,595 --> 00:10:35,175 Here is is hungry. 191 00:10:35,175 --> 00:10:40,140 We want to say if that hunger level 192 00:10:40,140 --> 00:10:41,415 reaches the threshold, 193 00:10:41,415 --> 00:10:44,295 we transition to this state changes, 194 00:10:44,295 --> 00:10:49,150 but then we also need to say self.current node, 195 00:10:49,610 --> 00:10:56,320 so the decision tree resets and self.build, 196 00:10:57,890 --> 00:11:05,350 which in a way, is a way of saying rebuild decision tree. 197 00:11:05,480 --> 00:11:10,065 This will take the current node back to the root node, 198 00:11:10,065 --> 00:11:12,120 and we're going to go through the chart again. 199 00:11:12,120 --> 00:11:14,970 In this case, now we're going to be hungry. 200 00:11:14,970 --> 00:11:19,245 What should be happening is that we are in wander state. 201 00:11:19,245 --> 00:11:20,490 We're in wander state for 202 00:11:20,490 --> 00:11:25,710 100 frames of hunger until the hunger level reaches 203 00:11:25,710 --> 00:11:30,180 this point and we transition out 204 00:11:30,180 --> 00:11:35,355 of hungry and we go into seeking food. 205 00:11:35,355 --> 00:11:38,850 Let's see if we're getting errors. 206 00:11:38,850 --> 00:11:41,235 We are running into an error here. 207 00:11:41,235 --> 00:11:47,590 Oh, yeah, I keep forgetting to self. 208 00:12:01,910 --> 00:12:04,960 Let's try it now. 209 00:12:06,830 --> 00:12:10,065 I'm wandering, and now, 210 00:12:10,065 --> 00:12:11,820 because we have multiple entries, 211 00:12:11,820 --> 00:12:13,710 this is going to start mixing up, 212 00:12:13,710 --> 00:12:16,155 but all of them start wandering, 213 00:12:16,155 --> 00:12:17,490 and then after 100 frames, 214 00:12:17,490 --> 00:12:19,395 they transition to seeking food. 215 00:12:19,395 --> 00:12:22,290 The way I would try this at this point, 216 00:12:22,290 --> 00:12:23,610 especially when you're working on the behavior 217 00:12:23,610 --> 00:12:25,365 of a decision tree, 218 00:12:25,365 --> 00:12:27,180 we probably don't want to be 219 00:12:27,180 --> 00:12:29,860 creating herbivores every frame. 220 00:12:31,370 --> 00:12:33,390 You probably want to create 221 00:12:33,390 --> 00:12:38,010 only one single herbivore which you 222 00:12:38,010 --> 00:12:44,220 could do not by running this in the run, but like here. 223 00:12:44,220 --> 00:12:46,305 You could say, Hey, 224 00:12:46,305 --> 00:12:48,390 let's create one herbivore 225 00:12:48,390 --> 00:12:50,430 that is situated in the middle of the screen, 226 00:12:50,430 --> 00:12:53,655 so that's 600 by 300. 227 00:12:53,655 --> 00:12:57,315 This is just a testing code. 228 00:12:57,315 --> 00:12:59,535 It's position is going to be that. 229 00:12:59,535 --> 00:13:02,950 That's a new herbivore added to the list. 230 00:13:05,210 --> 00:13:08,520 It's going to be there from the very beginning, 231 00:13:08,520 --> 00:13:11,880 but we are not creating herbivores dynamically. 232 00:13:11,880 --> 00:13:14,490 We can have one herbivore in the middle. 233 00:13:14,490 --> 00:13:15,720 It's wandering and eventually 234 00:13:15,720 --> 00:13:17,280 transitions into seeking food. 235 00:13:17,280 --> 00:13:19,875 If you want that transition to happen slower, 236 00:13:19,875 --> 00:13:24,040 you just need to give the herbivore a bit more time. 237 00:13:24,800 --> 00:13:29,650 You can say up to 300 frames. 238 00:13:30,650 --> 00:13:32,985 It's going to take a bit longer, 239 00:13:32,985 --> 00:13:36,795 and eventually will transition back into seeking food. 240 00:13:36,795 --> 00:13:38,220 We're going to get to a point where 241 00:13:38,220 --> 00:13:39,285 we're going to visualize 242 00:13:39,285 --> 00:13:42,590 those states more graphically. 243 00:13:42,590 --> 00:13:44,945 But yeah, it's conforming. 244 00:13:44,945 --> 00:13:47,300 You can do your own way of looking 245 00:13:47,300 --> 00:13:50,930 at printing out how much hunger level you have in 246 00:13:50,930 --> 00:13:53,060 relation to the hunger threshold that 247 00:13:53,060 --> 00:13:55,560 gives you an amount of 248 00:13:55,560 --> 00:13:59,385 the temporal duration of the wandering around 249 00:13:59,385 --> 00:14:01,860 until the animal actually 250 00:14:01,860 --> 00:14:04,275 starts feeling that it needs food. 251 00:14:04,275 --> 00:14:06,270 With that in mind, we're going to leave it here 252 00:14:06,270 --> 00:14:08,590 and we're going to see you in the next video.