UpdateWorld vs UpdatePhysics

[Roland]

Can anyone give some directions on when those should be used. What's the difference. I have in the example's that some actions are programmed in UpdateWorld and some in UpdatePhysics. I have a problem understanding the rule what to do where.

[reepblue]

UpdatePhysics is when the Physics calculation is being ticked while Updateworld is once per frame.

 

If you want something consistent regardless of framerate (such as fading out and such) use UpdatePhysics,

[Thirsty Panther]

My understanding of it is that update world occurs once every loop of your code. So navigation, particle emitter etc are acted out. While update physics occurs depending on the the speed of the CPU and happens every 2nd or 3rd loop of your main code. This takes care of movement and collisions of your models.

 

http://www.leadwerks.com/werkspace/topic/11632-updatephysics-vs-updateworld/

 

Interestingly there is no info on Update Physics in the API.

[Rick]

I believe UpdatePhysics() is called x times per second (30 or 60) where UpdateWorld() is called every cycle (dependent on how fast the CPU is). So when inside UpdateWorld() you want to use the speed in your movement calcs, but in UpdatePhysics() you know it'll be called x times per second and can rely on that. That means it may get called multiple times per frame or skip being called as it all depends on the CPU and how slow/fast it is to maintain the x times per second.

[gamecreator]

Interestingly there is no info on Update Physics in the API.

Yeah, this is the first thing I tried when I saw the thread. So: unofficial or undocumented? I'd love not having to use Time::GetSpeed() if there's a safe way to do it. There is this though: http://www.leadwerks.com/werkspace/page/api-reference/_/entity/entityupdatephysicshook-r62

[Roland]

Thanks all for the input. It makes it a bit clearer what the difference between the two callbacks are. As I have it now I have mouse-smoothing and such in UpdateWorld, seems that it would be better to have that in UpdatePhysics if I understand this correctly. Same for updating animations I guess.

[Josh]

Well, your mouse input could be read every update with UpdatePhysics, and it would be running at a constant 60 FPS, so no modulation is needed by the timing. However, this function can be skipped some frames, which would result in jittering motion.

 

You can get the mouse input every frame and then smooth it out when you apply it in the UpdateWorld function. This is how the physics systems makes motion smooth all the time, regardless of how fast your game runs. For example, the motion will be smooth even if your game is running at 120 FPS, because the motion is interpolated between the previous two frames of data.

 

That's fairly complicated stuff and you probably won't need to worry about it. Just remember that physics type stuff can be safeuly and easily handled in the UpdatePhysics() function, and it will always run at a constant speed. For stuff that the user expects to change each frame, like camera motion, UpdateWorld() is a better place to put this code, and you would multiply your values by Time:GetSpeed().

 

If your code is pure physics stuff, like handling the motion of a door by setting velocity, then put it in UpdatePhysics(). Otherwise UpdateWorld is best.

[Roland]

Thanks a lot Josh for the explanation