I am making a 2D car game like earn to die 2. I ve almost completed it. Only problem is the physics engine performance. I am using box2d and there are 10 meters length edge shapes totally building a 100 km terrain. 1 car and usually 30-40 boxes. Number of active dynamic bodies is around 60-100, max 120. Game fluently working in desktop but in android fps drops below 30 when actives bodies are more than 60. There are collisions between car and boxes and boxes each other and both box and car to ground.
I am using libgdx framework 1.9.4 as version, java is 1.7, coding with eclipse neon, windows 7.
this is how I am counting active bodies in world
int num=0;
Array<Body> bodies=new Array<>();
world.getBodies(bodies);
for(Body b:bodies){
if(b.isActive())num++;
}
active dynamic bodies are usually around 100
it is not a drawing issue with all terrain and underground meshes and car and boxes cost 6-7 mili seconds I measured them when box2d debug rendered is off and world step method call costs about 30 mili seconds when there are about 30 boxes while the car is crushing into them
I don't load all game objects (boxes for now) I splitted entire map into chunks map size is 100 km and chunk size is 50 meters when the car is in the next 50 meters ( in the chunk range) I load the boxes from a ready pool ( box2d world representations of the those objects are also pooled and when the boxes are in pool I deactivate their box2d body with setActive(false) and back to true while the chunk is loading)
I applied this chunk system for terrain too. I load all the terrain when the game is loading then deactivate them by setting with this method setActive(false) and when the car goes on trough the map if the chunk range includes car's x axis coordinate I activate the next chunk which contains the terrain static bodies having around 20 fixtures with size of 10 meters, makes the chunk size 200 meters at total.
the green lines are active terrain shapes as you see left and right after a distance are deactivated till the end of the map this part is from around 60 km of the map in middle of 100 km terrain map.
when vehicle moved little more new boxes will load there ahead and old ones will be pooled if they are 20 meters back from the car.
My questions are
1) is this fps (20 fps) normal and expected?(android 7 this is phone specifications http://www.androidpolice.com/2016/02/23/the-general-mobile-gm-5-plus-is-the-most-powerful-android-one-device-yet/)
2) can the 100 km terrain be problem if so how should I manage it?
->I tried activating/deactivating terrain bodies when they out of the screen rectangle.
->I tried hundreds of fixtures on a single body or every terrain piece is as separated body but best performance with I splited 100 km terrain into 200 meters chunks and each chunk is a body and consist of about 20 fixtures.
3) simulating 100 dynamic bodies with huge edge shape terrain is tottaly impossible ? ( but in the earn to die they did it)
4) should I write my own simple physics for only this kind of game (a simple specific one) ?
5) should I use bullet physics instead of box2d for 2D purposes ? is it possible? and will I face with performance problems ?
if you need any code pls comment, I will add.
are there any really fast physics engines I couldn't find on the net if there are do you suggest to change box2D ?
good to note:
I am simulating box2d with constant time step I tried 1/60 1/45 1/30 and 8-3 , 6- 2 as iteration steps.
I use high damping values like .9 for both linear and angular for all bodies.
I also would like to split those boxes into pieces actually I am doing it but without splitting hem when car crushed I am experiencing this fps drop so I disabled it for now.
Only joints are wheel joints and used for wheel of car no more joints in anywhere in map.
Sizes are realistic those boxes are 1.2 meters high.
for boxes and cars polygon shapes used for terrain edge shapes used (chain shape)
velocity threshold is 1 as default in world settings.
if there are any notes I forgot pls comment and I will share.
thank you.
