c++ - 快板帧率问题

Question

所以我最近在使用 Allegro 时遇到了一些问题。我不知道是什么原因造成的，但我会尽力在下面详细说明问题。

在我的主要功能中，我有这样的东西:

int main()
{
    Game *game = new Game();
    game->init(800, 600, 60); //width, height, framerate

    PlayState *playState = new PlayState(); //extends abstract class GameState
    game->setDefaultState(playState);

    game->startGame();

    gMemoryTracker.reportAllocations(cout);
    system("pause");
    return 0;
}

这工作正常，在每帧结束时打印耗时显示每帧大约 16.7 毫秒。然而，由于我希望 Game 类最终充当一个成熟的 GameState 管理器(目前它只支持一个 GameState)，我希望 Game 类的 init 函数调用每个 GameState 自己的单独 init 函数。显然，这意味着在调用 Game 的 init 函数之前注册每个 GameState，因此我将 main 函数更改为如下所示:

int main()
{
    Game *game = new Game();
    //this is where the call to init used to be

    PlayState *playState = new PlayState();
    game->setDefaultState(playState);

    game->init(800, 600, 60); //now this is called after we create a GameState and set it as default

    game->startGame();

    gMemoryTracker.reportAllocations(cout);
    system("pause");
    return 0;
}

问题是现在每帧渲染大约需要 1100 毫秒，即使 Game 类报告帧速率仍设置为 60fps。为了调试这个问题，我对 main 进行了最后一次更改:

int main()
{
    Game *game = new Game();   

    PlayState *playState = new PlayState();
    game->init(800, 600, 60); //now init is being called after we create a new GameState, but before we set it as default
    game->setDefaultState(playState);

    game->startGame();

    gMemoryTracker.reportAllocations(cout);
    system("pause");
    return 0;
}

但这会导致与以前相同的问题，每帧渲染大约需要 1100 毫秒。似乎这个问题只发生在我创建一个新的 GameState 后调用 init 时，所以我查看了 PlayState 类的构造函数和 Game 类的 init 函数，看看我是否能找到会导致这种行为的东西，但我仍然没能找到原因。您可以在下面找到上述两个函数:

bool Game::init(int width, int height, float frameRate)
{
    mFrameRate = frameRate;
    bool result = mpGraphics->init(width, height); //initialize the graphics system

    //this calls the init function for the default GameState. commented-out for debugging purposes
    //result = result && mpDefaultState->init();

    return result; //were all inits successful?
}



PlayState::PlayState() : GameState("play_state")
{
    //create required graphics buffers and fonts
    bgBuffer = new GraphicsBuffer(DISPLAY_SIZE.getX(), DISPLAY_SIZE.getY());
    woodsBuffer = new GraphicsBuffer(ASSET_PATH + "Woods.png");
    smurfBuffer = new GraphicsBuffer(ASSET_PATH + "smurf_sprites.png");
    font = new Font(ASSET_PATH + "cour.ttf", 12);

    smurfAnimation = new Animation(60, true); //create new animation for smurf walk cycle. args are animation framerate (must be <= game framerate) and loop animation

    //load sprites from spritesheet
    for (int y = 0; y < (int)SPRITE_SHEET_SIZE.getY() / (int)SPRITE_SIZE.getY(); y++)
    {
        for (int x = 0; x < (int)SPRITE_SHEET_SIZE.getX() / (int)SPRITE_SIZE.getX(); x++)
        {
            //there was already a class named Rectangle, so i had to get creative
            UnequalSquare uSquare(x * (int)SPRITE_SIZE.getX(), y * (int)SPRITE_SIZE.getY(), (int)SPRITE_SIZE.getX(), (int)SPRITE_SIZE.getY());
            smurfAnimation->addSprite(Sprite(*smurfBuffer, uSquare));
        }
    }
}

我还注意到的一件事是，如果我在 PlayState 的渲染函数中注释掉所有渲染调用，游戏会以正确的帧速率运行，但显然这不是一个可行的解决方案。我将在下面发布渲染功能。目前效率不是很高(每帧都创建新的 sprite 对象)，但这并不能解释为什么在创建 PlayState 实例之前调用 Game.init() 会完美运行。

void PlayState::render(GraphicsSystem* graphics, const Timer& frameTimer)
{
    // Create background
    Sprite bgSprite(*bgBuffer);
    graphics->fill(*bgBuffer, Color(255, 0, 0));

    // Create image
    Sprite woodsSprite(*woodsBuffer);
    Vector2D woodsLocation((DISPLAY_SIZE.getX() - (woodsSprite.getWidth() * WOODS_SCALE)) / 2.0, (DISPLAY_SIZE.getY() - (woodsSprite.getHeight() * WOODS_SCALE)) / 2.0);

    // Draw Text
    int fontWidth = font->getTextWidth(TEXT_STRING);
    int fontHeight = font->getFontHeight();

    for (int i = 0; i <= DISPLAY_SIZE.getY() / fontHeight; i++)
    {
        for (int j = 0; j <= DISPLAY_SIZE.getX() / fontWidth; j++)
        {
            graphics->drawText(*bgBuffer, Vector2D(j * fontWidth, i * fontHeight), TEXT_STRING, *font, Color());
        }
    }

    //update the animation
    smurfAnimation->update();

    // Draw sprites to backbuffer
    graphics->drawSpriteToBackbuffer(gZeroVector2D, bgSprite);
    graphics->drawSpriteToBackbuffer(woodsLocation, woodsSprite, WOODS_SCALE);
    graphics->drawSpriteToBackbuffer(gZeroVector2D, smurfAnimation->getCurrentSprite());
}

谁能看出我遇到此问题的任何原因？我已经研究了几个小时了，但我终究无法弄明白。

Answer 1

我发现了问题。来自 Allegro 5 文档:

Unless you set the ALLEGRO_MEMORY_BITMAP flag, the bitmap is created for the current display. Blitting to another display may be slow.

我试图在创建显示之前创建位图，因此导致性能不佳。设置 ALLEGRO_MEMORY_BITMAP 标志可显着提高帧速率，但每帧仍需要大约 100ms-200ms。我想这只是 Allegro 的一个弱点，我需要从现在开始考虑。

来源:https://www.allegro.cc/manual/5/al_create_bitmap