I need help about optimizing physics in mobile devices

Hello!

I have made a game which uses hundreds of objects with sphere colliders and rigidbodies. For the game design, I hold those objects in a jar like candies, and I need them to fall down like when the jar breaks as in the real world. I have tested with an iPhone 8, 10, 11 and Samsung Galaxy S8 which I have no significant lags but in others, especially in Android devices, it's like hell. I checked on profiler and it seems like the problem is mostly physics. I guess because those candies are constantly colliding with each other, physics engine go nuts and in most of the devices it's not handled easily.

If I make them not collide with each other by layer settings, they don't look like candies on top of each other like in a jar, instead they get inside of each other.
If I remove the rigidbodies or make them kinematic, the candies don't fall when the jar is broken. The jar is not supposed to be always completely broken, sometimes only some part of it gets broken and the objects inside spill down from the crack. So I couldn't figure out what to do.


I don't know much about the optimization, I'm still learning with Unity lessons, but I need urgent help in this case

You can see the attached image of profiler.

Thanks in advance!

 

Your main problem is just the sheer number of objects in your scene. It may simply not be possible on some slower phones to do the simulation in real time.

May I ask if this simulation needs to be dynamic each time? Will there be different candies and will they have to fall in a different way each time? If you can get away with it looking the same every time you do it, you could attach a https://docs.unity3d.com/2018.3/Documentation/ScriptReference/Animations.GameObjectRecorder.html to each object in the scene and create a preset animation for each object. Then you could play the animations back with Animators. This will be much more performant than doing real time physics.

 

Thank you so much! I really wanted it to be physics related game, so the candies fall depending on the broken jar parts and fall naturally. However, I didn't know about GameObjectRecorder at all! I will try to adapt this to the game in the worst case scenario.

 

Since it's a bit out of scope to explain exactly what your needs are, I can't be sure this is a wise suggestion, but you could make the candies particles that collide with the jar (but not each other). And then you can get callbacks when those collisions hit and visualy 'fill' the jar up as more and more candies hit your trigger. This requires a good deal of understanding of the particle system.

 

Thank you! I didn't know particles consume less than standard rigidbodies when it's come to physics, so I didn't even consider using particles in this option

 

Another possible option would be to utilize each candies "Awake" and "Asleep" physics state. I'm not actually sure how feasible this is, but the idea that came to mind is to have each candy cast a ray in a few directions (or maybe even just toward jar openings) and if they find that they are blocked by other candies, put the rigid body to sleep (or possibly even change it to kinematic). if they are able to ray cast to the opening without hitting other candies, then it may be their turn to fall, in which case the rigid body should be awoken, or turned back to dynamic if you switched it to kinematic.

The overall idea here is that it should be fairly cheap for each candy to cast just one, or maybe a few rays and if they can figure out that they won't need to move soon remove themselves from the simulation. You could possibly also optimize the performance of the ray casting by making them wait some amount of time between casts instead of just casting every Update or FixedUpdate.

 

Not sure what the game is, but perhaps it’s possible to do 2d physics?
Eg for a lot of my 3D games, I’ve used 2d physics, eg using box2d which is far computational less expensive than 3d

Also use the simplest collision shape possible, eg circle for 2d , sphere for 3d

 

Damn this is so practical! I heard of sleeping rigidbodies but this usage is something that I thought impossible! Thank you! <3

 

Yep, I already use 3d for sphere Thanks anyways!

 

Did you figure out a good way to do this? Did it work? Just asking because this might be the solution I'm looking for as well...

 

Hi! Actually I haven't, I delayed this project for another, but definitely would let this post know, and really appreciate if you would do so

 

I think you guys need to adjust physics time to reduce physics calculations that can help you alot

 

I know this is an old thread. But it's an issue I'm currently investigating myself. I used to play a game called Auralux (and the improved version Auralux: Constellations). Neither work on modern devices as the game is quite old. But it was able to have many thousands of physics objects with collisions even on very old mobile devices. I assume it was using some very naïve custom physics engine which focused more on performance than accuracy. But I'm struggling hard to implement something similar. Even Google created LiquidFun which is a custom Box2D engine that could render thousands of physics bodies and work on very old devices. And that was from 9 years ago.

Surely this can be done without using ECS?