I am writing a Tetris program with PyGame, and came across a funny problem.
Before I ask the question, here is the pseudo-code:
while True:
# In this part, the human controls the block to go left, right, or speed down
if a key is pressed and the block isnt touching the floor:
if the key is K-left:
move piece left one step
if the key is K-right:
move piece right one step
if the key is K-down:
move piece down one step
# This part of the code makes the piece fall by itself
if the block isnt touching the floor:
move block down one step
# This part makes the while loop wait 0.4 seconds so that the block does not move
# down so quickly
wait 0.4 seconds
The problem is that, because of the "wait 0.4 seconds" part of the code, the part that the human controls can only move every 0.4 seconds. I would like it so that the block moves as fast as the human can press the key, while at the same time, the block dropping every 0.4 seconds. How could I arrange the code so that it will do that? Thanks!
The main problem I see here is that you are limiting your framerate using a wait of 0.4 seconds.
You should not limit framerate, but instead, you should limit how fast your block falls.
If I remember well, there was a formula you could use to do just that. It was based on the amout of time elapsed since the last frame. It looked like:
fraction of a second elapsed since last frame * distance you want your block to move in a second
This way, you can keep your mainloop intact, and the move processing will happen at every frame.
You could also do...
...
# This part of the code makes the piece fall by itself
if the block isn't touching the floor and
the block hasn't automatically moved in the last 0.4 seconds:
move block down one step
...
Just realize you'll be doing a lot of polling if the user hasn't struck any keys.
You may try asking gamedev.stackexchange.com instead. Check the site for Game Loops, and check out other example pygame projects to see how they're doing it. Having a good game loop is essential and will take care of things for you such as user inputs and a consistent frame rate.
Edit: https://gamedev.stackexchange.com/questions/651/tips-for-writing-the-main-game-loop
When doing games you should always try to do something like this:
while not finished:
events = get_events() # get the user input
# update the world based on the time that elapsed and the events
world.update(events, dt)
word.draw() # render the world
sleep(1/30s) # go to next frame
The sleep time should be variable so it takes into consideration the amount of time spend drawing and calculating the world updates.
The world update method would look something like this:
def update(self, events, dt):
self.move(events) # interpret user action
self.elapsed += dt
if self.elapsed > ADVANCE_TIME:
self.piece.advance()
self.elapsed = 0
The other way of implementing this (so you dont redraw too much) is to have events fired when the user orders a piece to be moved or when ADVANCE_TIME time passes. In each event handler you would then update the world and redraw.
This is assuming you want the pieces to move one step at a time and not continuous. In any case, the change for continuous movement is pretty trivial.
I have a timer that calls the function 'bottleCreate' from 500 to 500 miliseconds. But I want that time to increase during the game (getting faster the creation of the bottles, and the game gets more difficult). But I don't know how to increase that variable inside new Timer. Thanks
interval=500;
var my_timer=new Timer(interval);
my_timer.addEventListener(TimerEvent.TIMER, bottleCreate);
my_timer.start();
You want the game to get faster, so the variable needs to decrease, because less time between function calls will make it faster.
According to the Documentation of the Timer Class you can use the delay variable to change the interval speed.
So, to make it faster, you could simply write
my_timer.delay -= 50;
Each time you do this, the function call will be called 50 ms faster.
Be aware though, going beneath 20ms will cause problems, according to the Documentation.
Furthermore, each time you manipulate the delay variable, the timer will restart completely, with the same repeat count you use at initialization.
I've written a basic velocity-based animation engine which iterates over a list of custom Shape objects which hold direction and velocity. When animating more than 500 objects, my application sees significant slowdown, but the actual time it takes to change the positions of the objects is very low.
Results are roughly as follows:
100 objects - <1ms modification time, 60 FPS
500 objects - 2ms modification time, 40 FPS
1000 objects - 4ms modification time, 10 FPS
I am currently using Timer-based animation, and my timer is set to 15ms intervals. The timer is the ONLY thing executing in my program, and the modification times I have listed measure the entirety of the timer's event function which contains only synchronous code. This means (as far as I can tell) that the only thing that could be responsible for the delay between timer events is screen rendering.
All my objects are tightly clustered. Would screen rendering really take four times as long for 1000 objects as 500? There is no opacity, and the only properties being edited are x and y values.
Specifically, I am wondering if there is a more efficient way to re-render content than changing the positions and then calling event.updateAfterEvent(). Any help is appreciated!
I'm having a setInterval AS3 problem.Let me explain: I'm making a game with a timer, lets for example give its instance, timer1.every 500 milliseconds timer1 moves to left 25 times (timer1.x-=25) and when timer1 hitTests finish1 (if(timer1.hitTestObject(finish1))) it goes to the you lose scene.and you have to replay the level.When I hit replay and enter the scene the speed increases in the setInterval by double and if I lose again, triple and so on.How do fix this? It's very important that I have it fixed soon.thanks
Sounds like multiple instances of timer1 are continuing to run.
1 instance of timer1 runs at original speed.
2 instances of timer1 runs at double speed.
etc.
Ensure that the original timer1 is stopped, deleted or killed off before changing scene.
You may want to reference the function clearInterval.
I'm having a silly-yet-serious case of coder's block. Please help me work through it so my brain stops hurting and refusing to answer my questions.
I want to fire a timer at intervals up to a final time. For example, if t = 0, my goal is 100, and my interval is 20, I want to fire at 0, 20, 40, 60, 80, and 100.
The timer is not precise, and may fire early or late. If it first fires at 22, I want to fire again in 18. If it first fires at 19, I want to fire in 21. All I know when the timer fires is the current time, goal time, and firing interval. What do I do?
Edit: Sorry, I wasn't too specific about what the heck I'm actually asking. I'm trying to figure out what kind of math (probably involving taking the modulus of something) needs to be done to calculate the delay until the next firing. Ideally, I also want the timer to by matched to the end time — so if I start the timer initially at 47, it schedules itself to fire at 60 and not at 67, so the last firing will still be at 100.
If the primitive functionality you have is "schedule X to fire once at time T", then your procedure handling X should know the time T0 at which it was supposed to fire (the time T1 at which it actually fired is not needed) as well as the desired firing interval DT and schedule itself for time T0+DT. If the primitive is "fire D from now", then it should schedule for D = T0+DT-T1 (if that's negative then it needs to schedule itself immediately again but record that the scheduled time and the "was supposed to fire at" time are different so it can keep compensating on following firings).
Somebody already mentioned that .NET's Timer does this for you; so does Python's sched stdlib module; so, I'm sure, do many other languages / frameworks / libraries. But in the end you can build it if needed on top of either of the single-scheduling primitives above (one for an absolute time or one for a relative delta from now) as long as you keep track of desired as well as actual firing times!_)
I would use the system clock to check your interval. For example if you know that your interval is every 20 minutes, fire off the first interval, check what the time was, and adjust the next interval start time.
If your language/platform's underlying timers don't do what you want, then it's usually best to implement timers in terms of "target times", which means the absolute time at which you want the timer to fire next. If you platform asks for an "absolute time", then you give it the target time. If it asks for a "relative time" (or, like sleep, a duration), then it is of course target_time - current_time.
The quick way to calculate each target time in turn is:
When you first set up the timer, calculate the "interval" (which might have to be a floating-point value, assuming that won't cripple performance) and also the "target time" of the first timer fire (again, you might need fractions). Record both, and set your underlying timer mechanism, whatever that is.
When the timer fires, work out the next target time by adding the interval to the previous target time.
The problem with that approach is that you might get some very tiny accumulating errors as you add the interval to the target time (or not so tiny, if you haven't used floats).
So the longer and more accurate way is to store the very first start time, the target finishing time, and the number of firings (n). Then you recalculate the target time for each new firing in turn, which makes sure that you don't get cumulative rounding errors. The formula for that is:
target(k) = start + ((target_end - start) * k) / n
Of if you prefer:
target(k) = (k/n) * end + (1-k/n) * start
Where the firings of the timer are k=1, 2, 3, ... n. I was going to make it 0-based, then realised that was daft ;-)
The last thing you have to wrestle with when implementing timers is the difference between "wall clock" time, and real elapsed time as measured by your hardware clock. Wall clock time can suddenly jump forwards or backwards (either by an hour if your wall clock is affected by daylight savings, or by any amount if the system's clock is adjusted or corrected). Real time always increases (as long as it doesn't wrap). Which you want your timer to respect depends on the intended purpose. If you want to know when your last bus leaves, you want a timer firing daily according to wall clock time, but most commonly you care about real time elapsed. A good timer API has options for these kinds of things.
Build a table listing the desired fire times, say 10:00, 10:20, 10:40, 11:00, and 11:20.
If your timer function takes an absolute time, the rest is trivial. Set it to fire at each of the desired times. If for whatever reason you can only set one timer at a time, okay, set it to fire at the first desired time. When that event happens, set it to fire again at the next time in the table, without regard to what time it is now. Each time through, pick up the next time until you're done.
If your timer function only accepts an interval, no big deal either. Find the difference between the desired time and the current time, and set it to fire at that interval. Like if the first time is 10:00 and it's now 9:23, set it to fire in 10:00 minus 9:23 equal 37 minutes. Then when that happens, set the interval to the next desired time minus the current time. If it really fired at 10:02, then the interval is 10:20 minus 10:02 equals 18 minutes. Etc.
You probably should check for the possibility that the next fire time has already passed. If the process can take longer than the interval you might run past it, and even if not, the system might have been down. If a fire time is missed, you may want to do catch up runs, or just skip it and go to the next desired time, depending on the details of your app.
If you can't keep the entire table -- like it goes on to infinity -- then just keep the next fire time. Each time through the process, add a fixed amount to the next fire time, without regard to when the current process ran. Then calculate the interval based on the current time. Like if you have a desired interval of 20 minutes going on forever starting at 10:00, and it's now 9:23, you set the first interval to 37 minutes. Say that actually happens at 9:59. You set the next fire time to 10:00 plus 20 minutes equals 10:20, i.e. base it on the goal time rather than the actual time. Then calculate the interval to the next fire time based on the current time, i.e. 10:20 minus 9:59 equals 21 minutes. Etc.