How to make async step timing (game loop) using Box2D and C++

Question

I'm making a game in C++ using Box2D and WebSocket++. The world needs to updated every 1/60 second. Meanwhile the WebSocket server handles players. How I should make the interval? I know there's no setInterval function in C++, but I can do something like this:

• make async function - https://stackoverflow.com/questions/33234403/using-setinterval-in-c/33234557

• make async thread - https://codereview.stackexchange.com/questions/40915/simple-multithread-timer

or maybe there's a lib?

Note: this isn't a duplicate of How should I write a main game loop? because here I need asynchronous game loop. In linked topic there are synchronous game loops.

Why I won't use while (sync loop):

commands after while (loop) are never excuted if loop is set to true.

@SethBattin I think no, because here I need asynchronous game loop (as another thread or async function). — Szymon Marczak, Aug 09 '16 at 12:26
Can you explain why it has to be asynchronous? It's not obvious from your question. — Seth Battin, Aug 09 '16 at 12:28
@SethBattin Edited the question. Commands after while (true) are never excuted. — Szymon Marczak, Aug 09 '16 at 12:30
@SethBattin I'll read input for excuting another commands made by me, such as kicking players etc... — Szymon Marczak, Aug 09 '16 at 12:32
If you want to poll input from another thread, why can't you do it from inside the while(true)? What's going to come after the loop? — Vaillancourt, Aug 09 '16 at 12:53
You don't need asynchronous game loop. You just need to call some part of code asynchronously/non-blocking. — Mars, Aug 09 '16 at 12:54
@Mars Thanks, I didn't think about that! If you can please add your answer so I can accept it :) — Szymon Marczak, Aug 09 '16 at 12:58

score 1 · Accepted Answer · answered Aug 09 '16 at 13:05

It looks you fell into "I need this!" scheme. But all you need is just call some specific part of game loop asynchronously or non-blocking.

How to achieve this? Make sure whole loop is executed 60 times every second. In more proper words: Make sure every iteration takes less than 16.(6) ms. If it takes longer (your loop "lagged"), make two (or more) updates next frame, so the average FPS remains constant. In the loop gather user input, network data, update game state, render. With this, you can have another thread running WebSocket or a non-blocking function that checks whether anything is in network buffer to read. If not, it returns immediately.

Anything past the while loop is... not a game anymore. Make some cleanup there or anything you find appropriate. Loop might take some bool isRunning as condition and be handled inside.

How to make async step timing (game loop) using Box2D and C++

1 Answers1