Box2D Painfully Slow Movement

[eddieone]

On certain computers, ones that wouldn't seem like they should lag, movement in my game is slow. When using `game.time.desiredFps = 30;` it also happens. My question is, how can I drop frames instead of making players swim through mud? Instead of looking ugly, it becomes unplayable. I tested this for p2, it also happens with that physics engine.

[alex_h]

Have you tried profiling with chrome dev tools to confirm that the physics really is the bottleneck?

[eddieone]

I have, to me it seems to be related to rendering. Though, it's not entirely clear yet. I'm going to try and remove a bunch of stuff to isolate if it is text or something like that. Still though, it would be nice to be prepared for slow devices.

[alex_h]

I had a similar situation a few weeks back where a game was running really slow on some older iPads and low spec devices. I also first assumed it was the physics, but when I profiled with chrome found it was rendering graphics API shapes that was killing the processor. When I removed the Graphics display objects the game ran perfectly on those problem devices. Solution was to detect non-retina iPads and disable the graphics API features for those platforms.

Isolating stuff like you mentioned is definitely the way to go in your case.

[eddieone]

Thanks for the tips. I haven't experienced the lag myself, I can only simulate it. Though, we have one machine with 6 core i7 and GTX 960, it's getting lag. I'm still collecting data, I'm hoping to pinpoint why some are getting 30-40 FPS on decent machines and others get solid 60 FPS. I read some where non bitmap text could cause slow downs, that that is my first choice for isolating the problem. We have a decent amount of text.

[alex_h]

PIXI.Text is automatically flattened to a single texture by default, which makes the whole text field display object no more expensive to draw than any other sprite. Text is probably not the culprit I reckon.

[eddieone]

We had 2 people report 30 FPS. After removing most text, they reported 55-60. Could be less tabs open or something.

Still text or not, there is a massive flaw with Phaser having physics tied to frame rates. It will cut off a huge chuck of the possible audience.

There is an old issue on github that explains it very well. https://github.com/photonstorm/phaser/issues/798

[eddieone]

I had to buy a netbook to figure it out but I found a way to get what I wanted. The following code will drop physics frames if you will and allow a player on a slow machine to almost move as fast as someone with 60 FPS. So instead of being ugly and slow, it's mostly just ugly now. I mean visually browsers will try to compensate by lowering quality.

 

// Put this in create or somewhere
game.time.advancedTiming = true;
game.physics.box2d.useElapsedTime = true;

// Put this in render
game.time.physicsElapsed = 1 / game.time.fps;