在不同的计算机上限制游戏的速度

Question

我正在使用OpenGL和C++创建2D游戏.

我想要它以便游戏在不同的计算机上以相同的速度运行,此时我的桌面上的游戏比我的笔记本电脑运行得更快(即我的播放器在我的桌面上移动得更快)

我被告知QueryPerformanceCounter()但我不知道如何使用它.

我该如何使用它还是有更好/更简单的方法？

我的显示功能

void display()                                  
{
static long timestamp = clock();
// First frame will have zero delta, but this is just an example.
float delta = (float)(clock() - timestamp) / CLOCKS_PER_SEC;

glClear(GL_COLOR_BUFFER_BIT);

glLoadIdentity();

createBackground();

int curSpeed = (player.getVelocity()/player.getMaxSpeed())*100;

glColor3f(1.0,0.0,0.0);
glRasterPos2i(-screenWidth+20,screenHeight-50);
glPrint("Speed: %i",curSpeed);

glRasterPos2i(screenWidth-200,screenHeight-50);
glPrint("Lives: %i",lives);

glRasterPos2i(screenWidth-800,screenHeight-50);
glPrint("Heading: %f",player.getHeading());

for(int i = 0;i<90;i++){
    if (numBullets[i].fireStatus == true){
        numBullets[i].updatePosition(player);
        if (numBullets[i].getXPos() > screenWidth || numBullets[i].getXPos() < -screenWidth || numBullets[i].getYPos() > screenHeight || numBullets[i].getYPos() < -screenHeight ){
            numBullets[i].fireStatus = false;
            numBullets[i].reset(player);
            numBullets[i].~Bullet();
        }
    }
}

player.updatePosition(playerTex,delta);

glFlush();

timestamp = clock();

}

我的更新positiom方法

void Player::updatePosition(GLuint playerTex, float factor){
//draw triangle
glPushMatrix();

glEnable(GL_TEXTURE_2D);    
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBindTexture(GL_TEXTURE_2D, playerTex);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

glTranslatef(factor*XPos, factor*YPos, 0.0);
glRotatef(heading, 0,0,1);
glColor3f(1.0,0.0,0.0);
    glBegin(GL_POLYGON);
        glTexCoord2f(0.0, 1.0); glVertex2f(-40,40);
        glTexCoord2f(0.0, 0.0); glVertex2f(-40,-40);
        glTexCoord2f(1.0, 0.0); glVertex2f(40,-40);
        glTexCoord2f(1.0, 1.0); glVertex2f(40,40);
    glEnd();

glDisable(GL_BLEND);
glDisable(GL_TEXTURE_2D);
glPopMatrix();

XPos += speed*cos((90+heading)*(PI/180.0f));
YPos += speed*sin((90+heading)*(PI/180.0f));
}

Answer 1

通常,您希望根据时间增量(即自上一帧以来经过的时间量)进行所有游戏性计算.这将标准化所有机器的速度.除非您需要极高的精度,否则可以使用clock()(from <ctime>)来获取当前时间戳.

例:

void main_loop() {
   static long timestamp = clock();
   // First frame will have zero delta, but this is just an example.
   float delta = (float)(clock() - timestamp) / CLOCKS_PER_SEC;

   calculate_physics(delta);
   render();

   timestamp = clock();
}

void calculate_physics(float delta) {
   // Calculate expected displacement per second.
   applyDisplacement(displacement * delta);
}

void render() {
   // Do rendering.
}

编辑:如果您想要更高的精度,您应该使用您的操作系统计时器功能.在Windows上,最精确的方法是使用QueryPerformanceCounter().例

#include <windows.h>

void main_loop(double delta) {
  // ...
}

int main() {
  LARGE_INTEGER freq, last, current;
  double delta;
  QueryPerformanceFrequency(&freq);

  QueryPerformanceCounter(&last);
  while (1) {
    QueryPerformanceCounter(&current);
    delta = (double)(current.QuadPart - last.QuadPart) / (double)freq.QuadPart;

    main_loop(delta);

    last = current;
  }
}

Answer 2

大多数游戏使用帧时间缩放因子。本质上，您会找到设置物理和运动的帧长度，并将其除以游戏运行的实际帧长度 (1/fps)。这会产生一个标量因子，您可以将其乘以运动的变化，以保持所有运动的一致性，同时保持提高 FPS 的好处。

一个很好的例子在这里。