2011-12-15 16:32, Nathan Sweet skrev:
>>setInterval(function gameflow() {
I think you're off to a good start with using setInterval.
I will probably change that to setTieout later though...
>>The game should update the location of all objects 250 times/sec
However, expecting to refresh rate to be 250hz is a little unrealistic.
Nicholas Zakas literally just published a good article on timer
resolution in browsers here it is:
http://www.nczonline.net/blog/2011/12/14/timer-resolution-in-browsers/
Good article. Some stuff that I'd missed. 4ms = 250 times per second I
had picked up from HTML5, but not that it was only for setTimeout and
that setInterval had a minimum of 10ms.
Let me just explain why I want 4ms.
An object that is 2 units away from a wall or a pong-paddle and that
moves towards it at a speed of 5 units of length per page refresh will
travel 3 units too far before a collision is detected. Worst case
scenario is that it will go through the wall or paddle. And even if that
happens the physics will be unrealistic. The ball won't bounce off the
wall, but inside it.
One way to avoid that is to make the math more complex, which generally
does not sit well with my students. It is doable for detecting a
collision with a wall, but when both objects are moving the formulas
will be way too complicated.
If one OTOH checks for collisions more frequently, as in 250 times per
second, the delta between each frame will be so small that the problems
will disappear. Hence my desire to separate in-memory math from
on-screen appearance.
Here is a good tutorial that does some simple collision detection stuff:
http://billmill.org/static/canvastutorial/
I think we've got some kind of handle on the actual collision detection
stuff, but I do appreciate the link.
If I may show you guys what a student of mine is doing, have a look at
http://keryx.se/lab/svg/pacman.php
It is being developed at
https://github.com/Hasselmannen/Pacman/blob/master/pacman.php
For this game we have no problems detecting collisions only 50
times/sec, but I expect some games to have objects moving a lot faster soon.
https://github.com/Hasselmannen/Pacman/blob/master/pacman.php
--
Lars Gunther
http://keryx.se/
http://twitter.com/itpastorn/
http://itpastorn.blogspot.com/
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