I'll definitely post the app tonight for you guys to check out (at
work now). I am an embedded systems programmer by trade. But I do
physics toys for fun and am just getting into Java/Android
optimizations. I will point out that optimizing for Java and
optimizing for Android are very different. As people have pointed out
before, the key things to be careful with on Android are memory
allocation and floating point math. I've removed both of these from
my physics loop. I also found that function call overhead was quite
large and had to manually inline all of my fixed point math code. I
think that with the correct spatial data structures I can get a couple
hundred objects interacting. I have a 2D rigid body physics engine
that is currently all C++ (no exceptions or templates or RTTI or
multiple inheritance) that I may port over as well.
However, having said all of that, I think it may be the case that
we will just have to wait until a native SDK is available to really
write a top notch physics engine. It's sort of the perfect example of
a piece of code that doesn't need anything more than libc and JNI
bindings. And since you only call it a couple times per frame the JNI
overhead would be well amortized.
Anton
On Mar 31, 9:17 am, mscwd01 <mscw...@gmail.com> wrote:
> Thanks for your feedback Shaun, I too unfortunately think a bespoke
> engine will need to be written for Android, which is a real pity as
> the iPhone has several physics engines which can easily handle
> hundreds of objects.
>
> Having said that Anton (2nd reply) has said he has an engine running,
> it would be nice to see a demo of this if that'd be possible?
>
> Clark, i'd definately host any .apk's on my own site, I wouldn't put
> it on the marketplace if it wasn't a "finished" app - do people
> actually do that?!
>
> I think i'll stay away from developing games with physics for the time
> being and concentrate on something else, I cant see it being feasible
> to include it any time soon which is a real pity.
>
> On Mar 31, 3:28 pm, shaun <shashepp...@gmail.com> wrote:
>
> > I am the author of simpull.
>
> > Sorry guys for the demo being out of whack for Simpull to the Core.
> > The version of PulpCore that I integrated simpull with did not support
> > Chrome, but you should be able to see it in IE, FF Safari. It is nice
> > to take a look at that demo to get a feel for what the engine is
> > capable of, but the performance does not translate over to the fixed
> > point branch/version of simpull when running on Android.
>
> > I ran tests on both the emulator and the actual device and there was a
> > significant increase in performance because of the fixed point
> > implementation, but I got very frustrated that it still did not
> > support the amount of objects in a scene that I considered good for a
> > physics-based game. It seemed to handle ~10 objects moving and
> > colliding OK. It has been a while since I was playing with it, so I
> > do not really remember the exact number of objects or the frame rate.
> > I mostly remember being upset with it.
>
> > I am leaving the physics ideas for games out of the picture when
> > thinking Android for now. Someone would have to write a ground up
> > engine with all the performance and memory concerns of Android in
> > mind, which was not the case with Simpull.....I created it for
> > applets, then thought to port over to fixed-point for Android. It
> > works well with small scenes, but certainly not the staple engine to
> > use in my opinion.
>
> > Also, Phys2D will not run worth a damn on Android. I tried it and I
> > even went through some heavy performance tuning. Garbage collection
> > is the major issue even after all I did. I seriously doubt JBox2D
> > will run well either. I'll stick to what I said earlier, a ground-up
> > solution by someone smarter than me is probably required.
>
> > On Mar 31, 9:49 am, "admin.androidsl...@googlemail.com"
>
> > <admin.androidsl...@googlemail.com> wrote:
> > > Not tried but if you can provide us with some example source code or
> > > put something on the market, I'm sure we could take a look.
>
> > > G1 performance is significantly faster than emulator, but there are
> > > limitations.
>
> > > Particularly with garbage collection and memory allocation on code
> > > that gets run continuously in loops, so I don't know how optimised
> > > these physics engines are for this purpose.
>
> > > Would be interesting to find out though.
>
> > > On Mar 31, 12:52 pm, mscwd01 <mscw...@gmail.com> wrote:
>
> > > > Oh I forgot to re-ask...
>
> > > > "Has anyone tested Phys2D or JBox2D on an actual device to see if they
> > > > run better than on the emulator?
>
> > > > I have a feeling the performance will better on a G1 than the emulator
> > > > for some reason!
>
> > > > On Mar 31, 12:51 pm, mscwd01 <mscw...@gmail.com> wrote:
>
> > > > > I did take a look at Simpull, however the demo application failed to
> > > > > run as it relied on some library which wasn't supplied or referenced
> > > > > to - I just got annoyed after spending two days failing to get Phys2D
> > > > > and JBox2D to work in Android and didn't bother trying to work out the
> > > > > problems!
>
> > > > > I might give it another look though...
>
> > > > > On Mar 30, 10:41 pm, Streets Of Boston <flyingdutc...@gmail.com>
> > > > > wrote:
>
> > > > > > I wonder how well this one works on Android:
>
> > > > > > http://code.google.com/p/simpull/
>
> > > > > > -- Anton Spaans
>
> > > > > > On Mar 30, 4:58 pm, Anton <socialhac...@gmail.com> wrote:
>
> > > > > > > I have a simple 2D physics engine written and running. It
> > > > > > > uses
> > > > > > > the now famous Jacobson physics tricks (Verlet integration and
> > > > > > > hard
> > > > > > > constraints). I can manage 40 balls on the screen, with fill n^2
> > > > > > > interaction between balls. I am working on spatial data structure
> > > > > > > optimizations now to improve the computational complexity of the
> > > > > > > collision detection code. I run the constraint update loop five
> > > > > > > times
> > > > > > > per frame and get 30 frames per second. Once the engine is up and
> > > > > > > running there are no memory allocations done in my program. And
> > > > > > > once
> > > > > > > the system settles down from the app launch there are very few GC
> > > > > > > events from other programs. Though they do still happen. Viewing
> > > > > > > LogCat I see a GC every 10 or 20 seconds because of some
> > > > > > > background
> > > > > > > application. But between those events I get a consistent frame
> > > > > > > rate.
> > > > > > > I am using OpenGL for my rendering.
>
> > > > > > > -Anton
>
> > > > > > > On Mar 30, 1:14 pm, mscwd01 <mscw...@gmail.com> wrote:
>
> > > > > > > > Does anyone know of, or have implemented, a physics engine
> > > > > > > > which runs
> > > > > > > > smoothly in Android?
>
> > > > > > > > I have spent the last couple of days trying Phys2D and JBox2D,
> > > > > > > > however
> > > > > > > > both perform very poorly - I am struggling to get even a few
> > > > > > > > objects
> > > > > > > > to simulate smoothly as frequent garbage collection spoils it.
>
> > > > > > > > One question I do have is will these run smoother on an actual
> > > > > > > > G1
> > > > > > > > device or is the performance of the emulator accurate?
>
> > > > > > > > Thanks- Hide quoted text -
>
> > > > > > > - Show quoted text -
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