Opengl: How do time based tetris game?

Question

I am working on a basic tetris game for school. I am not sure how can i develop a game loop since this is my first time making a game.

I am using opengl to do the drawing. Do I make a main loop that will wait certain amount of time before it redrawn the scene?

Answer 1

Here's a basic (very high level pseudo-code) game loop:

void RunGameLoop()
{
  // record the frame time and calculate the time since the last frame
  float timeTemp = time();
  float deltaTime = timeTemp - lastFrameTime;
  lastFrameTime = timeTemp;

  // iterate through all units and let them update
  unitManager->update(deltaTime);

  // iterate through all units and let them draw
  drawManager->draw();
}

The purpose of passing deltaTime (the time since the last frame in seconds) to unitManager->update() is so that when the units are updating, they can multiply their movement by deltaTime so their values can be in units per second.

abstract class Unit
{
  public:
  abstract void update(float deltaTime);
}

FallingBlockUnit::update(float deltaTime)
{
  moveDown(fallSpeed * deltaTime);
}

The draw manager is going to be responsible for managing the draw buffers (I suggest double buffering to prevent screen flicker)

DrawManager::draw()
{
  // set the back buffer to a blank color
  backBuffer->clear();

  // draw all units here

  // limit the frame rate by sleeping until the next frame should be drawn
  // const float frameDuration = 1.0f / framesPerSecond;
  float sleepTime = lastDrawTime + frameDuration - time();
  sleep(sleepTime);
  lastDrawTime = time();

  // swap the back buffer to the front
  frontBuffer->draw(backBuffer);
}

For further research, here's a book that my Game Programming professor wrote about 2d game programming. http://www.amazon.com/Graphics-Programming-Games-John-Pile/dp/1466501898