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POFixed timestep loop in C++
 

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    <p>I am trying to implement a fixed timestep loop so that the game refreshes at a constant rate. I found a great article at <a href="http://gafferongames.com/game-physics/fix-your-timestep/" rel="nofollow">http://gafferongames.com/game-physics/fix-your-timestep/</a> but am having trouble translating that into my own 2d engine.</p> <p>The specific place I am referring to is the function in the last part "The Final Touch" which is what most people recommend. This is his function:</p> <pre><code>double t = 0.0; const double dt = 0.01; double currentTime = hires_time_in_seconds(); double accumulator = 0.0; State previous; State current; while ( !quit ) { double newTime = time(); double frameTime = newTime - currentTime; if ( frameTime &gt; 0.25 ) frameTime = 0.25; // note: max frame time to avoid spiral of death currentTime = newTime; accumulator += frameTime; while ( accumulator &gt;= dt ) { previousState = currentState; integrate( currentState, t, dt ); t += dt; accumulator -= dt; } const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); } </code></pre> <p>For myself, I am just moving a player across the screen keeping track of an x and y location as well as velocity rather than doing calculus integration. **I am confused as to what I would apply to the updating of the player's location (dt or t?). Can someone break this down and explain it further?</p> <p>The second part is the interpolation which I understand as the formula provided makes sense and I could simply interpolate between the current and previous x, y player positions.</p> <p>Also, I realize I need to get a more accurate timer.</p>
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    1. COThat function is for the [integral from calculus](http://en.wikipedia.org/wiki/Integral). You seem to be asking about a timer event. These have nothing to do with each other.
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    2. CO@chrisaycock sorry for the confusion. question updated.
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    3. COYou certainly are confused, since you are doing integration but you say you're not doing integration. Yes, the integration from elementary calculus.
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      1. USDietrich Epp
 

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