Chipmunk 6.0.0 released. « cocos2d for iPhone

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Chipmunk 6.0.0 released.

(29 posts) (10 voices)

Started 10 months ago by slembcke
Latest reply from riq

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chipmunk

slembcke
Administrator
So I wasn't too sure if I'd get this done before going camping this weekend, but I did. \o/
http://chipmunk-physics.net/release/ChipmunkLatest.tgz

I just released 5.3.5 so I won't add a lot of fanfare to this. I've spent a ton of time working on this for the last 6+ months to get the new spatial index working well and all the changes to the contact graph and sleeping algorithms. While most of the work was cleaning up and optimizing the internals, there are a good number of new features as well.

Keep in mind that Chipmunk 6.x's API is not quite 100% compatible with 5.x. Make sure you read the list of changes carefully.
Also, keep in mind that this is a x.0.0 release and that it's likely there are still some bugs I don't know about yet. If you are near the end of a project, or bundling it with another library, I might hold off for a few weeks. For new projects, jump right in! I've spent a lot of effort rewritting the collision detection, sleeping, and contact graph algorithms that have required large changes and cleanup to the 5.x codebase. I've ironed out all the bugs that I know of, and the beta test went well. So it's finally time for 6!

Next up is creating a ton of new example material. From what I gather from feedback, one of the biggest problems with Chipmunk is that there isn't enough example material. I'm going to create new demos that actually show off more interesting things that you can do, popup inline examples in the docs for a lot of the sections, and a number of new tutorials.

CHANGES SINCE 5.x:
- API: Chipmunk now has hard runtime assertions that aren't disabled in release mode for many error conditions. Most people have been using release builds of Chipmunk during development and were missing out on very important error checking.
- API: Access to the private API has been disabled by default now and much of the private API has changed. I've added official APIs for all the uses of the private API I knew of.
- API: Added accessor functions for every property on every type. As Chipmunk's complexity has grown, it's become more difficult to ignore accessors. You are encouraged to use them, but are not required to.
- API: Added cpSpaceEachBody() and cpSpaceEachShape() to iterate bodies/shapes in a space.
- API: Added cpSpaceReindexShapesForBody() to reindex all the shapes attached to a particular body.
- API: Added a 'data' pointer to spaces now too.
- API: cpSpace.staticBody is a pointer to the static body instead of a static reference.
- API: The globals cp_bias_coef, cp_collision_slop, cp_contact_persistence have been moved to properties of a space. (collisionBias, collisionSlop, collisionPersistence respectively)
- API: Added cpBodyActivateStatic() to wake up bodies touching a static body with an optional shape filter parameter.
- API: Added cpBodyEachShape() and cpBodyEachConstraint() iterators to iterate the active shapes/constraints attached to a body.
- API: Added cpBodyEeachArbiter() to iterate the collision pairs a body is involved in. This makes it easy to perform grounding checks or find how much collision force is being applied to an object.
- API: The error correction applied by the collision bias and joint bias is now timestep independent and the units have completely changed.
- FIX: Units of damping for springs are correct regardless of the number of iterations. Previously they were only correct if you had 1 or 2 iterations.
- MISC: Numerous changes to help make Chipmunk work better with variable timesteps. Use of constant timesteps is still highly recommended, but it is now easier to change the time scale without introducing artifacts.
- MISC: Performance! Chipmunk 6 should be way faster than Chipmunk 5 for almost any game.
- MISC: Chipmunk supports multiple spatial indexes and uses a bounding box tree similar to the one found in the Bullet physics library by default. This should provide much better performance for scenes with objects of differening size and works without any tuning for any scale.
Posted 10 months ago #
Birkemose
Moderator

It is insanely impressive, that we get tools like this shoved up our ... computers.

My first question would be how this impacts on Objective Chipmunk?

Posted 10 months ago #
riq
Key Master

Thanks. Great work!

or bundling it with another library, I might hold off for a few weeks

Thanks for the advice. cocos2d v1.0.0 will include chipmunk v5.3.5

Posted 10 months ago #
pfg2009
Member

Thanks @slembcke! You are my personal hero!

Posted 10 months ago #
wilczarz
Member

@slembcke, are you planning to write these examples also for the Obj-C wrapper, or will you focus mostly on the core C library?
EDIT: I just found out that the wrapper is a separate project so I suppose my question is obsolete ;)

Posted 10 months ago #
slembcke
Administrator

@Birkemose: Objective-Chipmunk 5.3.5 and 6.0 is all ready to be sent out. The mass emailings for every new version has been getting really cumbersome so we will be setting up a private login section on the new Chipmunk website for people that purchased Objective-Chipmunk. It will have downloads for all the versions and an RSS feed to keep people connected when new versions come out. I'll be back to my computer on Tuesday and that's the very first thing I have planned. Don't worry, we haven't forgotten about the people that have helped support us financially. :)

Also, Objective-Chipmunk is going to be renamed to Chipmunk Pro soon as we will be adding features beyond just the ObjC wrapper. The auto-geometry code I've been experimenting with is pretty much good to except for an ObjC API, and I've also been working on a multithread collision detection algorithm and solver so people can squeeze even more physics performance out of the iPad 2 and such. This of course will be free upgrade from Objective-Chipmunk purchases. ;)

@riq: Yup. 5.3.5 might not have all the latest bells and whistles, but it's pretty well battle tested.

@pfg2009: Thanks! Now I just have to get working on that example code.

@wilczarz: The plan is to try and split the time about 50/50 so that people that have bought Objective-Chipmunk don't feel gypped, and that the users of the open source core don't feel that we've sold out on them. ;)

Posted 10 months ago #
Birkemose
Moderator

Cant wait to see the Pro package :)

In my opinion Obj Chipmunk is in a league of its own. The ease of use is almost scary, maybe also because the approach to adding bodies to a space, is identical to adding sprites to a layer.

There are minor things, like angle in stead of rotation, and pos in stead of position, but those are all minor issues.
The biggest complaints for me would be the lack of help at your fingertips ( like cocos2d has ), and better ObjC examples.
I personally think both of those are big issues.

A detailed description of the differences in collision detection from box2D would also be nice, and how to avoid the chipmunk pitfalls. I think many chooses box2D because of the "failsafe" collision detection, and I myself had quite a few "aha" moments, before I understood the basics. On the other hand, the ultra fast collision detection really is amazing.

Posted 10 months ago #
ehoffman
Member

@Birkemose I've read some older topics about Chipmunk vs. Box2d. As the last one is C++ I decided to use it some time ago. Now I checked again the Chipmunk docs, the Chipmunk forum, ... It's time to give it a try. From what I can see it is more active developed and the features ...

In my opinion Obj Chipmunk is in a league of its own.

So can you share some thoughts about Chipmunk vs. Box2d?

Posted 10 months ago #
ehoffman
Member

@slembcke This is a quote from your homepage:

such as the terrain of your game. Fortunately, the days of typing in coordinates are gone! Chipmunk Pro includes some tools that can efficiently create collision shapes for objects based on images.

What do you mean with this?

Posted 10 months ago #
slembcke
Administrator

@birkemose:

The biggest complaints for me would be the lack of help at your fingertips
What do you mean by that exactly? I have doxygen generated docs for Objective-Chipmunk, though it's written assuming that you already read the basic C API docs.

@ehoffman: That's the auto-geometry stuff I was talking about earlier. Chipmunk pro will have libraries to take an anti-aliased image mask and vectorize it. You can then just draw a level in photoshop and have Chipmunk Pro automatically generate the collision outline when you load it. I used it to generate the collision outline for this from a black blob shaped thing I drew in photoshop: http://files.slembcke.net/upshot/upshot_GUMeCMxZ.png Even on the iPhone, it runs fast enough that you could do Worms style deformable terrain with it without dropping frames.

It can also make collision shapes for sprites, but at the moment it only fits convex polygons to them.

Posted 10 months ago #
ehoffman
Member

@slembcke Thank you for you answer :)

How many poly points do you have for this example using your algorithm?

EDIT: And btw. I read somewhere Chipmunk can handle convex polygons only - no concave polygons. Is this still correct?

Posted 10 months ago #
Birkemose
Moderator

@slembcke

What do you mean by that exactly? I have doxygen generated docs for Objective-Chipmunk, though it's written assuming that you already read the basic C API docs.

I mean Alt+Cmd+Doubleclick directly into the help file. I really missed that in the beginning.

And that autogenerated stuff sounds like a real bonus. Building even a simply space, so far is a lot of drawing on paper, and counting pixels.

@ehoffman
I certainly would not diss box2d, and many will be discouraged by the 200$ pricetag on obj chipmunk, but I think the abstraction level of objective chipmunk is much better than ccbox2d, and suits cocos2d better. You dont want the physics engine to be to high level, and not to low level either, and in that respect obj chipmunk matches cocos2d spot on. It really works like an extension.
Also, I like the fact, that it is not 3.rd party.
I know all this maybe doesnt matter, and I am sure that ccbox2d does a superb job for those who use it.

Posted 10 months ago #
ehoffman
Member

@Birkemose I would never ask to diss anything (or something/someone). But for all things there are pros and cons. Especially for software ... you for sure know the guys discussing Linux vs. Windows vs. Mac OS vs. choose whatever you like ;)

And I personally think $200 for good software is not that much. In my daily work (the reason why I was away from this forum for almost 2 month) I need to use software more expensive - but by definition it is expensive, because you have to use it (german law).

I've never used ccbox2d - always plain Box2d. But I made some tests with Chipmunk the last days, because I want to see if it works better for my special task. I've got it working in Box2d (SVN), but not 100% as I want it. So I just compare ...

What do you mean with this:

A detailed description of the differences in collision detection from box2D would also be nice, and how to avoid the chipmunk pitfalls. I think many chooses box2D because of the "failsafe" collision detection, and I myself had quite a few "aha" moments, before I understood the basics.

Did you use Box2d before or did you start with Chipmunk and stick to it?

regards, Eike

Posted 10 months ago #
Birkemose
Moderator

At first I looked at box2d and chipmunk, and from that I started with box2d, because in chipmunk I had to write stuff like body->v, and body->u. What the heck is that?
But I never got box2d to work. I felt the way I had to set things up was cumbersome, and it was just a pain integrating it into cocos.

Then I found objective chipmunk, with property names that made sense, and an interface that matched cocos 100%. I think ccbox2d came after that. I had a look at the interface, and while it looks great, the abstraction level simply IMO is less toolbox like.
The bottom line is, that while many of us could write the code behind cocos, chipmunk or many other toolboxes, very very VERY few of us, can wrap it up in an interface that is easy to understand and still super flexible. That is IMO why cocos2d and obj chipmunk are superior toolboxes.

In the tech department, as I understand it, and I could be mistaking :)

Box2D uses a swept collision system, basically a raycasting system where collision is predicted before it happens. The benefit is that no collision is in theory missed, but as always, it eats up CPU cycles.
Chipmunk uses a "does this polygon overlap that polygon" collision system, meaning that if you have small fast moving objects, they could pass each other undetected. Also, a single drop in framerate could mess it all up ( in my first snowglobe, all snow vanished through the globe, when the phone rang, and FPS dropped to 1 )
So in chipmunk it is ex MUCH more important to use a fixed timestep, than in box2d.

But chipmunk can handle a lot of bodies, and I am a speed freak. The snowglobe runs 30 fps on a 3G with 400 snowflakes, and I really couldnt care less, if a single collision was missed. That is VERY impressive, and not because I made something fancy. Its all down to the raw speed of chipmunk.

Another theory of mine is, that you can "mess" more with the bodies in chipmunk than in box2d, because there is no "predicted" collisions in chipmunk. At least I have done a lot of frame based manupulation of objects, and it has never screwed up the physics.

Thinking about it. Still would be nice to have a raycast function in chipmunk.

Posted 10 months ago #
ehoffman
Member

like body->v, and body->u

Good old C pointer ;)

I agree, the ObjC interface of Chipmunk is really good. It's made as intended (by Apple) - you can read it [object doOnBodyA:... bodyC: apply:...]. But I, for example, come from C/C++ ... so I often use plain C (and I don't "know" that I do it). This is the great thing about ObjC, it's basically C (ok C++, too, but that's another discussion).

many of us could write the code behind cocos, chipmunk

Uhh, no, I disagree. Maybe other toolboxes, but I'm sure not Box2d, Chipmunk or Cocos. There is a lot more behind the scenes than what you can see on the first glance (or the second, third, ...). That is one reason why these frameworks are so popular (and we all use them, but do not write our own). Today I had a look on the gles20 branch of cocos2d. Never mind, someone said to me "Someday you will do CFD on your clock" ... at least on my phone I can do it already (ok, with some help of the GPU and just Euler, but...).

Back topic: Box2d has CCD - continous collission detection. This is switched on by default in the cocos2d templates. If you switch it off you will get a lot more performance from box2d. CCD is implemented -as I understood it- by just following the path the body would have moved between every time step (yes raycasting, some kind of) - calculating everything in between. And Box2d has a different broadphase than Chipmunk - don't ask me what exactly that means.

So I'm not sure if the performance is that much different between both.

But the learning curve is steep, for both of them. Tomorrow I think I will see if what I want to do works better in Chipmunk or in Box2d. :)

Posted 10 months ago #
Birkemose
Moderator

many of us could write the code behind cocos, chipmunk

Uhh, no, I disagree. Maybe other toolboxes, but I'm sure not Box2d, Chipmunk or Cocos.

Okay, maybe I was a bit optimistic there ;) The point was, that the real hard part is wrapping it all up in a flexible interface.
In that respect cocos is probably the best I have ever seen. The ease of use, and power available, is mind boggling.

I didn't know you could disable continuos collision in box2d, but of cause you can, and in that case I would be surprised if box2d was slower than chipmunk.
I still think the obj C interface of chipmunk is brilliant though.

Posted 10 months ago #
araker
Moderator

An interesting conversation about the differences (and simularities) between box2d and chipmunk can be found on the tigsource.com site. Slembcke and one of the authors of box2d talk about their frameworks. If you don't know it already, it's one of the best topics about box2d in relation to chipmunk and vice versa.

Posted 10 months ago #
ehoffman
Member

@araker Yes, I know this thread. Good information, but a little bit older I think.

Posted 10 months ago #
slembcke
Administrator

Some benchmarking I did a couple months back comparing Chipmunk 6b to Box2D 2.1.2 with CCD turned off:
https://spreadsheets.google.com/spreadsheet/ccc?key=0ApnIlzE8tqk6dG1fQWl4NFNrNFhlTmZ3ZlVUdFJFdUE&hl=en_US#gid=0

You can see what the benchmark simulations look like if you run the Chipmunk demo app on the command line with the -bench argument.

I'm waiting until I have time to finish implementing the multithreading and Arm NEON optimizations in Chipmunk Pro before releasing the numbers too publicly though. I doubt it'll be able to double the performance over the numbers in the spreadsheet, but it's already proving to be a pretty big bump.

Posted 10 months ago #
ehoffman
Member

@Birkemose As I wrote yesterday, I started to "port" to (Objective) Chipmunk, just as a test. So far I've not finished it, but yes the interface is very clean. My code looks good :) Good interfaces are complicated (for whatever kind of interface)... Apple is good at user interfaces btw.

Currently I use the trial version of ObjC-Chipmunk, because for testing the nag screen is ok. But I think I'll stick with it. The physics behavior is a bit more "developer friendly" - as I feel.

And @slembcke the spreadsheet is really interesting :) Thank you!

Posted 10 months ago #
wybielacz
Member

Can somebody point me how to update my current cocos2d project with chipmunk 5.3.4 to chipmunk 6.0.0 ?
When i just copy over the new files and replace the old with the new ones then i get some errors and I do not know how to fix them.
The errors are like:
space->staticShapes - doesn't exist
space->activeShapes - doesn't exist
cpSpaceResizeStaticHash() - implicit declaration
cpSpaceResizeActiveHash() - implicit declaration

Posted 10 months ago #
slembcke
Administrator

cpSpace.staticShapes/cpSpace.activeShapes are part of the private API. About a year ago I started tagging structs and functions to mark them as private and have been warning people (on forums, in the documentation, and in the README) that with Chipmunk 6 they would be gone. You can still enable access to the private API if you wish (It's in the docs), but I'm trying to make it very clear going forward with 6.x that using the private API is done at your own risk and may not be compatible even between minor versions.

If you are doing this:
cpSpaceHashEach(space->staticHash,...)
cpSpaceHashEach(space->acviteHash,...)

Do this instead:
cpSpaceEachShape(space, ...)

cpSpaceResize*Hash() are simply gone because Chipmunk only supported spatial hashing before 6.0. Now Chipmunk supports several spatial indexes and the default one requires no tuning and still gets better performance most of the time. Forget that the cpSpaceResize*() functions ever existed.

Posted 10 months ago #
hm50
Member

@MobileBros have you had time to look at a quick fix for the "klass" errors in SpaceManager when using CP6.0? Can I just rename "klass" to something else?

Posted 10 months ago #
mobilebros
Moderator
Well perhaps @slembcke has a better answer, but the not-so-good way to do would be to do:
```
cpShapeType type = shape->CP_PRIVATE(klass)->type;
```
Posted 10 months ago #
wybielacz
Member

I still can't get Chipmunk 6.0.0 to work after upgrading from 5.3.4!
Can somebody post how the step function and eachShape should look like ?

Posted 10 months ago #
slembcke
Administrator
@hm50, @mobilebros: Yes that will work, but as part of the private API may change without notice. When I make object oriented wrappers I just make subclasses for each of the shape types and use the language's native type system to check.

@wybielacz: cpSpaceEachShape() works almost exactly like how people were using cpSpaceHashEach(), but in an officially supported way.
```
static void drawShape(cpShape *shape, void *myPtr)
{
  ...
}
...
cpSpaceEachShape(space, drawShape, myPtr);
```
Posted 10 months ago #
wybielacz
Member

@slembcke
Thanks! I could finally get everything to work :)

Posted 10 months ago #
hm50
Member

Great! Thanks for the answers! I'll give it a shot when i get home!

Posted 10 months ago #
riq
Key Master

Chipmunk v6.0.1 integrated into cocos2d v2.x.

Posted 9 months ago #

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