Question

我正在学习SDL，我正在尝试创建一个Pacman游戏。我试图采取措施，以免陷入大量的代码陷入困境。

到目前为止，我已经创建了一个空白窗口并在其上呈现了Pacman图像。我可以按箭头键并将Pacman移动到窗口周围。我设置好了，所以Pacman图像存储为SDL_Texture，我使用RenderCopy将其blit到窗口。每次用户按下箭头时，我移动图像的坐标并重新渲染整个图像。这很好用。然而，现在，我想在屏幕上放一些点，让吃豆子吃。如果我加载一个点图像并将其作为一个新的纹理存储到与屏幕一起显示在屏幕上，然而，每次我移动吃豆人时，点闪烁进入，因为它被删除并与Pacman一起重新渲染。

我的问题是，如何避免这种“闪烁”？我可以以某种方式重新渲染Pacman而不重新渲染屏幕的其余部分吗？或者还有另一种方法吗？我想我在后面尝试创建迷宫时也会遇到同样的问题。如何制作每次重新渲染时不会闪烁的静态背景？

以下是我的代码。如果那里有任何不良形式的代码，请原谅我。正如我所说，我刚刚开始学习SDL（对C ++也很新），所以如果有任何明显的“你永远不应该这样做！”在那里的东西，我会很感激任何人指出：）

#include <iostream>
#include <SDL2/SDL.h>
using namespace std;

const int WINDOW_HEIGHT = 480;
const int WINDOW_WIDTH = 640;
const int MOVE_WIDTH = 10;

int main(int argc, const char * argv[])
{
    SDL_Window* mainWindow = NULL; //To hold the main window
    SDL_Renderer* renderer = NULL; //To hold the renderer
    SDL_Rect targetRect; //Rectangle to which pacman image will be drawn
    SDL_Surface* bmpSurface = NULL; //To hold bmp image
    SDL_Texture* bmpTexture = NULL; //To hold bmp image

    //Initialize SDL and check for errors
    if ( SDL_Init(SDL_INIT_EVERYTHING) != 0 )
    {
        cout << "ERROR: could not initialize SDL." << endl;
    }

    //Create a window
    mainWindow = SDL_CreateWindow("BAM", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH, WINDOW_HEIGHT, 0);

    if (mainWindow == NULL)
    {
        cout << "ERROR: could not initialize mainWindow." << endl;
    }

    //Initialize renderer
    renderer = SDL_CreateRenderer(mainWindow, -1, SDL_RENDERER_ACCELERATED);

    //Load image and store in an SDL_Surface
    bmpSurface = SDL_LoadBMP("/Users/billgrenard/Desktop/Programs/SDL/SDL_KeyPresses/SDL_KeyPresses/pacman_closed.bmp");
    if ( bmpSurface == NULL )
    {
        cout << "ERROR: could not load bmp file." << endl;
    }

    //Convert surface to texture for rendering
    bmpTexture = SDL_CreateTextureFromSurface(renderer, bmpSurface);
    if ( bmpTexture == NULL )
    {
        cout << "ERROR: could not convert bmp surface." << endl;
    }

    SDL_FreeSurface(bmpSurface);

    //Define rectangle where pacman image is to be blitted
    targetRect.w = 30;
    targetRect.h = 30;
    targetRect.x = (WINDOW_WIDTH/2) - (targetRect.w/2);
    targetRect.y = (WINDOW_HEIGHT/2) - (targetRect.h/2);


    //Main game loop
    while (1)
    {
        SDL_Event e;
        if (SDL_PollEvent(&e))
        {
            //Quit when user x's out the window
            if (e.type == SDL_QUIT)
            {
                break;
            }

            //If user presses a key enter switch statement
            else if( e.type == SDL_KEYDOWN )
            {
                switch ( e.key.keysym.sym ) {
                    //If user presses up arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_UP:
                        if ( targetRect.y - MOVE_WIDTH > 0 )
                        {
                            targetRect.y -= MOVE_WIDTH;
                        }

                        break;

                    //If user presses down arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_DOWN:
                        if ( targetRect.y + MOVE_WIDTH < (WINDOW_HEIGHT - targetRect.w) )
                        {
                            targetRect.y += MOVE_WIDTH;
                        }

                        break;

                    //If user presses right arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_RIGHT:
                        if ( targetRect.x + MOVE_WIDTH < (WINDOW_WIDTH - targetRect.w) )
                        {
                            targetRect.x += MOVE_WIDTH;
                        }

                        break;

                    //If user presses left arrow and the resulting move is inside the window, then move the Pacman's position
                    case SDLK_LEFT:
                        if ( targetRect.x - MOVE_WIDTH > 0 )
                        {
                            targetRect.x -= MOVE_WIDTH;
                        }

                        break;

                    default:
                        break;
                }
            }
        }

        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, bmpTexture, NULL, &targetRect);
        SDL_RenderPresent(renderer);       
    }

    SDL_DestroyWindow(mainWindow);
    SDL_DestroyTexture(bmpTexture);
    SDL_DestroyRenderer(renderer);
    SDL_Quit();

    return 0;
}

编辑：在回答raser的评论时，这里是我找到PollEvent示例的链接：http://wiki.libsdl.org/SDL_CreateRenderer?highlight=%28%5CbCategoryAPI%5Cb%29%7C%28SDLFunctionTemplate%29

Answer 1

用于渲染Pacman的上述方法实际上可以很好地将点渲染到屏幕上。只需在新纹理中存储点的图像，创建一个SDL_Rect来保存此纹理，然后使用SDL_CreateRenderer将点图像与Pacman一起渲染到屏幕上。只要您没有使用像SDL_Delay之类的东西来减慢帧速率，您就会注意到渲染之间没有闪烁的点。

在SDL中渲染静止图像

1 个答案: