闪烁的背景颜色

Question

我使用SDL2创建了一个OpenGL窗口，但背景在黑色和黄色之间切换。

#include <SDL2/SDL.h>
#include <GL/glew.h>

#define SCREEN_WIDTH 500
#define SCREEN_HEIGHT 500

int main( int argc, char** argv )
    {
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 3 );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE );
    SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
    SDL_GL_SetAttribute( SDL_GL_ACCELERATED_VISUAL, 1 );

    SDL_Window* gWindow = SDL_CreateWindow( 
        "Title", 
        SDL_WINDOWPOS_UNDEFINED, 
        SDL_WINDOWPOS_UNDEFINED, 
        SCREEN_WIDTH, 
        SCREEN_HEIGHT, 
        SDL_WINDOW_OPENGL);
    SDL_GL_CreateContext( gWindow );

    glewExperimental = GL_TRUE;
    glewInit();

    glPointSize(3);
    glClearColor(1,1,0,0);
    glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
    glClear(GL_COLOR_BUFFER_BIT);
    SDL_GL_SetSwapInterval(1);

    int quit=0;
    SDL_Event event;

    while( !quit )
        {
        while(SDL_PollEvent( &event ))
            {
            if( event.type == SDL_QUIT )
                quit = 1;
            }
        SDL_GL_SwapWindow( gWindow );
        }
    SDL_DestroyWindow(gWindow);
    return 0;
    }

我希望背景为黄色，如glClearColor（1,1,0,0）所定义，在程序运行时不会闪烁。代码中有什么问题吗？

Answer 1

闪烁的原因是你正在使用双缓冲但不清除其中一个黄色缓冲区（即请注意你在代码中只调用一次glClear）。

我建议你每帧都打电话给glClear。要修复代码，可以将调用移到循环中，就在SDL_GL_SwapWindow之前：

while( !quit )
{
    while(SDL_PollEvent( &event ))
    {
        if( event.type == SDL_QUIT )
            quit = 1;
    }

    glClear(GL_COLOR_BUFFER_BIT);
    SDL_GL_SwapWindow( gWindow );
}