It's maybe a bit off topic, but how do you know that Android's gc is rudimentary? Have you got a link handy? I only found this: http://developer.android.com/guide/practices/design/performance.html
On Thu, Apr 2, 2009 at 11:59 PM, Anton <[email protected]> wrote: > > Shaun, thanks for checking it out. Yah, I agree that the real > complexity of a physics engine comes from joints and contact > constraints. The constraints in my demo are simple minimum distance > constraints. I have a 2D rigid body physics engine that I'm thinking > more and more about porting over to Android as well. This demo was > more of a calibration for myself to see how much computation I can do, > and what optimizations lead to the largest improvements. I'll > probably turn it into a fun toy for the Market and then look into > rewriting my rigid body engine for Android. > > Reading through Simpull I noticed that you allocate a new Vector3f > in your Verlet update routine. I think that will be a killer on the > Android platform because of it's rudimentary garbage collector and > limited RAM. My solution was to allocate an array of fixed point > numbers, four per ball. Effectively a vector pool that didn't require > any management because the number of balls never changed. > > On Apr 2, 6:31 am, shaun <[email protected]> wrote: > > I took a look at Anton's demo on a G1 device, and I was glad to see > > the integration of accelerometer as it really added value. I assume > > the calculations for collision detection and response are fairly > > basic, which allows for that performance. > > > > Simpull will also provide good performance for a scene of that nature > > (all verlet, no joints). At least I believe it will. The point where > > simpull becomes slow is when a more complex scene is in play with 10s > > of objects with many joints connecting some of them. Since the engine > > is all verlet and no rigid body dynamics, joints are one way to > > acheive a similar result, but with a very bad performance hit due to > > all the new temporary objects and new calculations. > > > > I would be super impressed to see a demo like Anton's with rigid body > > dynamics involved with at least some rectangles, if not other polygons > > and perhaps a joint or two. That is where the performance degrades > > quickly in my experience. > > > > On Apr 1, 2:45 pm, mscwd01 <[email protected]> wrote: > > > > > Thanks Lajos for pointing APE out, I hadn't heard of it until now. > > > > > Unfortunately your link to your Android port is broken, can you mend > > > it as I dont fancy spending another hour porting another library to > > > Android :D > > > > > Thanks > > > > > On Mar 31, 9:50 pm, lkelemen <[email protected]> wrote: > > > > > > Hello everyone, > > > > > > I was also disappointed with jbox2d's performance so I checked APE > > > > (Actionscript Physics Engine) fromhttp://www.cove.org/ape/. > > > > It was converted to java (http://www.cove.org/ape/java_ape.zip) so I > > > > started to convert the java version to Android. > > > > > > The performance is quite OK for 10-20 objects at the first start of > > > > the app but if you exit with the back key and restart it form the > > > > installed copy > > > > (either in the emulator or on the dev phone) then it gets slower and > > > > slower with each start. If you restart it from the emulator (by > > > > reinstalling it) then it is faster again. > > > > Neither the pressed keys are not working (probably it is because of > my > > > > poor Android programming knowledge). > > > > > > Here is a zipped Android project of it. Please experiment with it and > > > > send results to here i.e. is it slow for you also after re-re-re-.. > > > > staring?www.kotiposti.net/lkelemen/android/testape2d.zip > > > > > > thanks > > > > Lajos Kelemen > > > > > > On Mar 31, 9:26 pm, shaun <[email protected]> wrote: > > > > > > > I started going down the path of Object pooling. It seemed the > only > > > > > solution when taking an existing engine and making work on a > resource > > > > > constrained system like Android on a phone. Determining the > strategy > > > > > for returning objects to the pool proved quite tough for me. I > have > > > > > no doubt there are some experts on embedded systems programming > with > > > > > tons of experience with object pooling. We just would be too lucky > if > > > > > that person(s) was also experienced with Java, physics engines and > had > > > > > a passion for open source and games! Is that too much to ask? > LOL!! > > > > > > > On Mar 31, 12:17 pm, mscwd01 <[email protected]> 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 <[email protected]> wrote: > > > > > > > > > I am the author ofsimpull. > > > > > > > > > Sorry guys for the demo being out of whack forSimpullto the > Core. > > > > > > > The version of PulpCore that I integratedsimpullwith 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 ofsimpullwhen 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 withSimpull.....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, "[email protected]" > > > > > > > > > <[email protected]> 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 <[email protected]> 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 <[email protected]> wrote: > > > > > > > > > > > > I did take a look atSimpull, 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 < > [email protected]> > > > > > > > > > > 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 <[email protected]> > 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 <[email protected]> > 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 -- Hide quoted text - > > > > > - Show quoted text - > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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