cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   Zhenmuron
   Member

   Hi everyone!

   I am programming a platform type game using cocos2d, and have a question regarding some collision trouble. Basically its not about the actual programming, rather what is considered necessairy in a game. I have no problems at the moment, 60 fps and smooth. But if i stress the program by spawning ALOT of enemies and get the frame rate to drop below 10fps, sometimes the enemies/ player will drop through platforms and not detect the collision. I can do some hacks to avoid this, but is it generally
   required to prepare for situations like this? Thanks :)

   Posted 1 year ago #
2. 

   lordbritishix
   Member

   I don't know about the solution but for me, I don't even allow my FPS to go down to 40 - let alone 10 :) I think it's unacceptable! As for the collision detection not getting detected, unless it's run in an asynchronous way, I don't think it should skip..

   Posted 1 year ago #
3. 

   hm50
   Member

   Are you using a physics engine or writing your own collision code? 10fps is pretty slow, how many is "A LOT"? Can you post code examples of your collision detection?

   Posted 1 year ago #
4. 

   araker
   Moderator

   Yes always anticipate for the worst case scenario.

   You don't want the frame rate to drop that much, that will make the game feel sluggish. Improving the performance should be your goal here. I don't know how you are spawning those enemies, but if you are allocating a lot of sprites every frame that will slow your game down a lot. Allocating those sprites when the level is initialized and reusing them should speed things up considerably.

   What do you mean by a lot, what is the maximum amount per frame ?

   edit hm50 and lordbritishix beat me to it :)

   Posted 1 year ago #
5. 

   mobilebros
   Moderator

   I'm guessing you're using a physics engine but even if you're not most collision detection takes dt into consideration, since your "physics step" routine is probably getting called less times per second this means your dt is going to be higher and unless your using box2d with swept collisions.... you're going to have some penetration ;). If you really wanted to live with 10 FPS you'd want to split dt even smaller when you hit the physics step and repeat the step by the same number you split dt by.... of course this will also have the effect of giving you worse FPS.... guess there's no silver bullet for this one.

   Posted 1 year ago #
6. 

   max9xs
   Member

   @Zhenmuron:

   First of all I suggest to maintain FPS for your game...

   Do one test, Use debug draw and set the opacity of every sprite to 0 value..
   This will give you maximum FPS possible in your game..

   You will get the idea how can you increase the FPS.

   http://allseeing-i.com/Performance-tips-for-Cocos2d-for-iPhone

   There are several steps to reduce it...

   1 -> As boundary of your platform do not use cpSegmentshape..
   Use polygon shape for your boundary.

   2 -> Decrease the mass of the your dynamic bodies as compared to static shapes...

   3-> Adjust damping ratio for your game.

   4 -> Adjust Gravity for your game

   5 -> Maintain your FPS..using setAnimationInterval

   6 -> Set perfect Hash(static and dynamic) value for your space

   1=> At very slow FPS sometimes, poly shape even not detects, This is limitation of physics engine, due to design flow...

   If this happens in my game, i hack the chipmunk function locally to maintain such thing.(not much idea but one tricky shot helps me in this). I know this is not good thing, so i generally avoid these kind of "games" even..

   2,3,4 => bad steps generally ever,---- But we are the God in our physics system we have power to do..! Use power !

   5,6 => These is general ways to improve the FPS, you can easily find on cocos2d forum..

   I am getting 60 FPS in my iPod Touch 2G( slowwest iphone version ) with debug draw ..
   which contains 250 circle balls and four sided boundaries..

   Cheers..

   Max

   Posted 1 year ago #
7. 

   Zhenmuron
   Member

   Hey everyone, thanks you the replies! Sorry for the slowness, went to bed right after the post =)

   I am currently not using any physics engine, just coding my own collision detection.
   The AI is also very very basic at this point, haven't implemented it for real yet, but its pretty much the equivalent of a mushroom in the basic supermario games. Just to give you an idea.

   Anyway, when I say many i'm spawning about 400 enemies on the screen (pre created, just "sleeping" until spawned). Now I will never want to use that many enemies in the game at the same time, but I wanted to see the effect of freeze type spikes and low fps.

   The problem only occurs on a special type of block where I have a sprite, and define a line for where the player/npc will "walk". This type of block also allows the player to jump through it, but stops the player if he lands on it. Im very new to objective C and cocos2d so this part is a bit intimidating, but here is my code for that object :P

   - (void)checkCurveCollision:(CCNode*)target // target is either player or npc
   {
      for (int i=0; i<[points count]-1; i++) { // "points" is an array containing coordinates that define the curve (ground).
   
         if ((target.position.x >= [[points objectAtIndex:i] position].x) && (target.position.x <= [[points objectAtIndex:i+1] position].x)) { // Checks which set of points the player is between (sloppy I know)
   			float yPos;
   			if ([[points objectAtIndex:i] position].y > [[points objectAtIndex:i+1] position].y) { // checks if its downhill or uphill
   				yPos = (([[points objectAtIndex:i+1] position].x - target.position.x) * [[points objectAtIndex:i] angle]) + [[points objectAtIndex:i+1] position].y;
   			}
   			else {
   				yPos = ((target.position.x - [[points objectAtIndex:i] position].x) * [[points objectAtIndex:i] angle]) + [[points objectAtIndex:i] position].y;
   			}
   			if (self.passable == 1) { // passable just means you can jump through it
   				if ((target.position.y - ([(Player*)target rect].size.height/2) + helpValue) > yPos) { // Here is the check where the error occurs. By increasing "helpValue" I can change the area where the block will "swing" you back up to the edge.
   					[(Player*)target collideWithGround:yPos];
   				}
   			}
   			else {
   				[(Player*)target collideWithGround:yPos]; // Normal collide
   			}
   			break;
   		}
   	}
   }

   I can change the helpValue where the block swings you up onto the edge to fix the problems with npcs falling through. But then the player will snap onto edges by just being close, which looks very buggy. Hopefully its not to dirty code =) Thanks again

   Edit: I also just noticed that it can hold up at 10-15fps, but the npcs fall through when the game freezes for a frame. Lets call it lag in lack of a better word ^

   Posted 1 year ago #

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