我想做的是:
start a timer;
calculate and render stuff;
wait until time==enough;
首先;我听说windows中的GetTickCount函数的精度很低。这是真的吗?
第二;如果它不准确。我应该用什么代替?
第三;有没有其他方法可以限制基于闪电战的游戏中的帧数?
假设这是针对windows的,请注意,Visual Studio 2012和2013只使用std::chrono::high_resolution_clock的标准ticker(默认64hz,BeginTimePeriod()为1000hz可选),因此最好使用性能计数器,它在Vista及更高版本上运行的频率约为3mhz(或XP上的cpu时钟频率)。以固定频率运行的线程的示例,并且与Windows XP兼容,其中睡眠(1)可能需要长达2毫秒的时间。dwLateStep是一种调试辅助工具,每次周期过长时都会增加(如果可能的话,它会赶上)。延迟是基于计数器的原始读数(使用uWait和uRem),因此在很长一段时间内不会发生漂移。
typedef unsigned long long UI64; /* unsigned 64 bit int */
#define FREQ 400 /* frequency */
DWORD dwLateStep; /* late step count */
LARGE_INTEGER liPerfFreq; /* 64 bit frequency */
LARGE_INTEGER liPerfTemp; /* used for query */
UI64 uFreq = FREQ; /* process frequency */
UI64 uOrig; /* original tick */
UI64 uWait; /* tick rate / freq */
UI64 uRem = 0; /* tick rate % freq */
UI64 uPrev; /* previous tick based on original tick */
UI64 uDelta; /* current tick - previous */
UI64 u2ms; /* 2ms of ticks */
UI64 i;
/* ... */ /* wait for some event to start thread */
QueryPerformanceFrequency(&liPerfFreq);
u2ms = ((UI64)(liPerfFreq.QuadPart)+499) / ((UI64)500);
timeBeginPeriod(1); /* set period to 1ms */
Sleep(128); /* wait for it to stabilize */
QueryPerformanceCounter((PLARGE_INTEGER)&liPerfTemp);
uOrig = uPrev = liPerfTemp.QuadPart;
for(i = 0; i < (uFreq*30); i++){
/* update uWait and uRem based on uRem */
uWait = ((UI64)(liPerfFreq.QuadPart) + uRem) / uFreq;
uRem = ((UI64)(liPerfFreq.QuadPart) + uRem) % uFreq;
/* wait for uWait ticks */
while(1){
QueryPerformanceCounter((PLARGE_INTEGER)&liPerfTemp);
uDelta = (UI64)(liPerfTemp.QuadPart - uPrev);
if(uDelta >= uWait)
break;
if((uWait - uDelta) > u2ms)
Sleep(1);
}
if(uDelta >= (uWait*2))
dwLateStep += 1;
uPrev += uWait;
/* fixed frequency code goes here */
/* along with some type of break when done */
}
timeEndPeriod(1); /* restore period */