WEBVTT 00:00.670 --> 00:05.930 Work on an example to tie everything we've learned so far. 00:07.440 --> 00:18.480 Essentially what this program will do is we'll be able to control kind of a little ball or be a kid 00:18.910 --> 00:27.200 or something and we'll be able to move it around with our arrow keys. 00:27.780 --> 00:31.200 So first things first say it 00:33.780 --> 00:37.720 screen we don't want any echo 00:40.180 --> 00:43.630 in we don't want to see cursor 00:48.590 --> 00:55.850 falls in it we don't want any delay in our input 01:03.940 --> 01:11.500 and last thing is we want to keep it. 01:11.750 --> 01:18.910 So these functions will probably be using a lot for all the programs right. 01:18.950 --> 01:24.460 Well really just the Ngee that we're going to do in the next section. 01:24.790 --> 01:26.750 I'm going to have a quick. 01:26.930 --> 01:28.040 Just last time 01:31.780 --> 01:38.610 it means say it in a. 01:39.410 --> 01:55.510 Because otherwise it won't be able to understand or our arrow is in for it's yo Actually if you try 01:55.530 --> 02:05.240 with a character in a little warning and it'll say you can't compare each key down and keep it in everything 02:05.240 --> 02:06.440 like that with the input. 02:06.480 --> 02:09.670 So use it here. 02:09.820 --> 02:11.060 So say it while 02:13.640 --> 02:14.740 nocked quit 02:17.800 --> 02:21.050 and you will get the input. 02:24.620 --> 02:41.950 And if the input is not q then we will synch lead jousts clear the screen 02:44.890 --> 02:54.600 and then we'll just sort of check see what he were using and put each. 02:54.790 --> 03:02.120 He down. 03:02.350 --> 03:05.310 And then we'll move our ball down. 03:05.590 --> 03:10.370 If in each is he 03:13.070 --> 03:18.590 ball up it's input such. 03:23.210 --> 03:29.210 Laughs as if it's 03:31.920 --> 03:33.020 he right. 03:35.740 --> 03:36.150 OK. 03:36.350 --> 03:39.700 So what should we do in these cases. 03:39.710 --> 03:51.240 Well we'll need some variables here and we need the inch current exposition and set to be zero. 03:51.470 --> 04:02.100 You don't need current wives as well that G-0 and and in these since 04:04.500 --> 04:08.360 y goes down we'll say current age 04:10.900 --> 04:12.850 iPods plus plus. 04:12.880 --> 04:14.200 Right. 04:14.290 --> 04:20.650 And if it goes up we'll see current each minus minus. 04:20.730 --> 04:22.690 So we're going to move the ball. 04:22.870 --> 04:30.330 One one space every time we type the art is similarly 04:33.400 --> 04:36.680 it's minus here left. 04:36.880 --> 04:39.960 X is 04:43.350 --> 04:48.940 ch it correctly. 04:52.920 --> 04:58.880 Is pas plus. 04:59.120 --> 05:12.070 And then we actually draw the all ch you or Y pause or it's always Y then X 05:15.000 --> 05:17.500 in the ball will just draw. 05:17.690 --> 05:18.190 It's 05:22.210 --> 05:25.300 fresh. 05:25.990 --> 05:28.240 Otherwise we press. 05:28.240 --> 05:34.540 Q So which what caused this. 05:34.930 --> 05:38.760 So take a look at how this worked out. 05:39.070 --> 05:47.310 And it. 05:47.530 --> 05:52.840 Here we see ball. 05:53.000 --> 05:54.310 It's pretty good. 06:01.440 --> 06:05.800 Move it up and down right. 06:07.260 --> 06:09.250 Everything is looking pretty good. 06:18.300 --> 06:19.490 Is that 06:24.320 --> 06:28.990 and also at the end here. 06:31.490 --> 06:33.720 Don't forget that as well. 06:33.740 --> 06:36.490 Some could have some problems later. 06:39.440 --> 06:45.150 There is one more thing that we can do to this. 06:45.360 --> 06:47.830 It's kind of less obvious. 06:47.940 --> 06:54.650 But right now it runs basically acts kind of full speed. 06:54.650 --> 07:04.640 It's running as fast as you can possibly go which possibly could mess up our games in that our games 07:04.760 --> 07:06.740 might run far too fast. 07:06.800 --> 07:13.230 Maybe if the aliens are dropping bombs on us we won't be able to actually get out the way in time. 07:13.230 --> 07:14.410 Right. 07:14.610 --> 07:19.670 We're going to react so to fix this. 07:19.670 --> 07:22.040 I'm going to include 07:24.550 --> 07:36.410 mood seedtime and basically With time when I'm going to do is to limit how fast this loop will go as 07:36.450 --> 07:37.650 initially. 07:37.740 --> 07:49.730 So let's say I want to draw 60 times per second which is kind of the standard refresh rate of Monk. 07:49.810 --> 07:50.650 OK. 07:50.820 --> 07:57.150 And we say that it's 60 frames per second and you can think of one frame as being one time through the 07:57.150 --> 07:59.580 loop for our probes. 07:59.580 --> 08:07.940 So the question becomes how do we make sure that we're only doing 60 frames per second. 08:08.490 --> 08:19.080 And essentially what we're going to do is appear we're going to get the current time and we're going 08:19.080 --> 08:29.080 to use this type called clock clock and the squirty and it's going to give us the current time in clock 08:29.080 --> 08:32.320 ticks and it's playing with a clock tick is it. 08:32.320 --> 08:35.750 Second and to get the current time we need a function. 08:35.760 --> 08:41.040 And it's called clock. 08:41.100 --> 08:42.720 So this will give us 08:45.600 --> 08:46.800 current time 08:50.690 --> 08:52.870 in clock ticks 08:55.960 --> 09:15.400 and now we're going to do is up here are going to get the time again so we're I clock the new time 09:18.510 --> 09:33.000 equal to clock against the clock ticks again and we're going to say clock t delta time t is time between 09:33.000 --> 09:36.480 the new time and the current time 09:41.620 --> 09:51.770 so essentially DTC is how much time has passed from the last time we checked clock essentially. 09:51.780 --> 10:03.070 So this DTC is measured in clock ticks which is an arbitrary unit for measuring internal system time 10:03.540 --> 10:07.790 and it's dependent on your computer. 10:08.450 --> 10:12.360 But clock ticks by themselves don't really help too much. 10:12.420 --> 10:19.980 We need to somehow relate it to second since we want to only go 60 frames per second. 10:20.100 --> 10:32.370 So to get how many ticks per second time actually has a constant called clock ticks per second clocks 10:32.370 --> 10:39.560 per sec clocks her set like this. 10:39.560 --> 10:44.670 And this tells us how many clock ticks happen in a second for your system. 10:44.990 --> 10:54.650 OK so now we have to relate the EDT which is in Tick's two clocks per second. 10:54.980 --> 11:02.300 So to do that we're going to say clocks per second divided by some amount and the amount we're going 11:02.300 --> 11:08.080 to be or it's going to be is Konst in frames per second. 11:08.270 --> 11:16.130 And Ron said it to be 60 in this case and we're going to divide the clocks per second by our frames 11:16.130 --> 11:17.480 per second. 11:19.990 --> 11:28.040 This and essentially is going to be ticks per second divided by frames per second. 11:28.420 --> 11:35.470 And if you know your division you'll know that this kind of translates into ticks per frame. 11:35.970 --> 11:38.030 OK. 11:38.230 --> 11:44.130 So that's essentially what did he really is it's how many ticks per one frame. 11:45.320 --> 11:50.320 And so now we can actually compare this to the delta time. 11:50.330 --> 11:57.170 So we'll see if E.T. is greater than this. 11:57.370 --> 11:58.190 So if. 11:58.240 --> 12:05.430 How much time has passed is greater than our frame rate in ticks per frame. 12:05.690 --> 12:11.560 Then will do all of this. 12:13.440 --> 12:17.620 This is kind of format it's 12:21.050 --> 12:22.100 like that. 12:22.230 --> 12:30.220 They are into this whole thing in this kind of loop or in this case. 12:30.280 --> 12:30.870 Yes. 12:31.940 --> 12:35.940 So are going to check to see how much time is has 12:38.690 --> 12:41.860 as occurred since the last time it's a clock. 12:41.870 --> 12:49.970 And then if it's greater than our frame rate in ticks per frame rate this is what this basically amounts 12:49.970 --> 12:55.130 to is expert frame then we'll do all this. 12:55.130 --> 12:59.280 And the last thing we need to do is update current time to 13:03.090 --> 13:06.830 to the last times and since new time. 13:06.960 --> 13:15.260 OK so current time will be now what it was when we last checked which is equal to Newton. 13:15.550 --> 13:19.860 And so now if we run this 13:22.720 --> 13:29.050 you see that everything kind of looks exactly the same as what we did before. 13:29.230 --> 13:35.200 But like I said now it's going only 60 frames per second. 13:35.650 --> 13:44.880 And again that's going to help us with our game so that we can kind of limit how fast everything goes. 13:44.930 --> 13:48.210 So we might not use 60 frames per second. 13:48.410 --> 13:51.950 You might use it here. 13:52.400 --> 13:57.530 We might use like 20 French second to make it a bit nicer. 13:57.650 --> 13:58.680 OK. 13:58.680 --> 14:01.080 So that's it for this example. 14:01.430 --> 14:05.150 And in the next lecture I want to go over attributes.