cocos2d for iPhone

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

1. 

   MrMojo
   Member

   What I'm trying to achieve is collisions with ground shapes like the ones in Soosiz:

   

   I'm guessing that this could be done with collisions with a closed Bezier Path? Or with a B-Spline?

   I seen that the cocos source has functions like bezierat, which I could use to test for intersection with a bezier, but are there better intersection methods, or better curve types to use?

   I'm not necessarily looking for code (of course, that would be nice), but I'd like to know where I should be looking (names of algorithms, best data structures to represent curves, etc)

   Thanks in advance.

   Posted 1 year ago #
2. 

   gaminghorror
   Member

   Wild guess: if it's possible to figure out which parts of a texture are alpha-only and which aren't i would go for a simple alpha check - everything that's not alpha is walkable, the rest isn't.

   The other alternative is to write a little converter tool that takes the level's background image, or the layout if it consists of multiple images, or just the sprites individually and does that for you. So you'll end up with an array of bits written to a datafile which you load in the game for collision checks. So that for each pixel coordinate in the level you either have the blocking bit set or not and it becomes a simple lookup, probably with a little bit-shifting since you want to conserve memory as much as possible by using every bit in a byte.

   The last solution is probably the best in terms of computational performance and memory but requires additional "offline" tools. I think that's worth it if you do this kind of game. But i have no idea how computationally expensive bezier calculations really are, maybe they are completely cheap but then there's the question - how do you edit these? You'd probably still need tools or even a level editor of some kind.

   Posted 1 year ago #
3. 

   MrMojo
   Member

   thanks for the feedback. I'm wondering if I have to do some proximity / data caching (ie not use the bezier curves themselves, but generate data from them).

   Just minutes ago I came across this function, CGPathContainsPoint, which I know is intended for Core Graphics usage, but since it's just working against a data structure, I might be able to use it as mentioned in this Stack Overflow post:

   http://stackoverflow.com/questions/870631/iphone-map-clickable-non-rectangular-areas

   and the CGPath reference is here:

   http://developer.apple.com/Mac/library/documentation/GraphicsImaging/Reference/CGPath/Reference/reference.html

   Since it's a native API function, it might be fast? Of course my intent would be to use the function to map out the paths and do hit testing on them, but draw them using OpenGL...

   Posted 1 year ago #

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