SDL + OpenGL应用程序：空白屏幕

Question

我花了三天的时间尝试使用SDL + OpenGL创建一个小应用程序。该应用程序本身运行良好 - 除了它从不输出任何图形;只是一个黑屏。

我压缩了一个最小的C文件，我希望有人能给我一些指导。我正在用尽想法。

我正在使用Windows Vista，MinGW & MSYS。预先感谢您的任何建议！

#include <SDL/SDL.h> 
#include <SDL_opengl.h> 

size_t sx=600, sy=600, bpp=32; 

void render(void) { 
    glEnable(GL_DEPTH_TEST);        // enable depth testing 

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);     // clear to black 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  // clear color/depth buffer 
    glLoadIdentity();          // reset modelview matrix 

    glColor3b(255, 0, 0);         // red 
    glLineWidth(3.0);          // line width=3 
    glRecti(10, 10, sx-10, sy-10);       // draw rectangle 

    glFlush(); 
    SDL_GL_SwapBuffers(); 
} 

int input(void) { 
    SDL_Event event; 
    while (SDL_PollEvent(&event)) 
     if (event.type == SDL_QUIT || (event.type == SDL_KEYUP && event.key.keysym.sym == SDLK_ESCAPE)) return 0; 
    return 1; 
} 

int main(int argc, char *argv[]) { 
    SDL_Surface* surf; 

    if (SDL_Init(SDL_INIT_EVERYTHING) != 0) return 0; 
    if (!(surf = SDL_SetVideoMode(sx, sy, bpp, SDL_HWSURFACE|SDL_DOUBLEBUF))) return 0; 

    glViewport(0, 0, sx, sy);   // reset the viewport to new dimensions 
    glMatrixMode(GL_PROJECTION);  // set projection matrix to be current 
    glLoadIdentity();     // reset projection matrix 
    glOrtho(0, sx, sy, 0, -1.0, 1.0); // create ortho view 
    glMatrixMode(GL_MODELVIEW);   // set modelview matrix 
    glLoadIdentity();     // reset modelview matrix 

    for (;;) { 
     if (!input()) break; 
     render(); 
     SDL_Delay(10); 
    } 

    SDL_FreeSurface(surf); 
    SDL_Quit(); 
    exit(0); 
} 

更新：我有一个可行的版本，但它改变正交透视。我不知道为什么这个工程和其他没有，但以供将来参考，这里是可用的版本：

#include <SDL/SDL.h> 
#include <SDL_opengl.h> 

size_t sx=600, sy=600, bpp=32; 

void render(void) { 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 

    glLoadIdentity();          // set location in front of camera 
    glTranslated(0, 0, -10); 

    glBegin(GL_QUADS);          // draw a square 
     glColor3d(1, 0, 0); 
     glVertex3d(-2, 2, 0); 
     glVertex3d(2, 2, 0); 
     glVertex3d(2, -2, 0); 
     glVertex3d(-2, -2, 0); 
    glEnd(); 

    glFlush(); 
    SDL_GL_SwapBuffers(); 
} 

int input(void) { 
    SDL_Event event; 
    while (SDL_PollEvent(&event)) 
     if (event.type == SDL_QUIT || (event.type == SDL_KEYUP && event.key.keysym.sym == SDLK_ESCAPE)) return 0; 
    return 1; 
} 

int main(int argc, char *argv[]) { 
    SDL_Surface *surf; 

    if (SDL_Init(SDL_INIT_EVERYTHING) != 0) return 0; 
    if (!(surf = SDL_SetVideoMode(sx, sy, bpp, SDL_OPENGL))) return 0; 

    glViewport(0, 0, sx, sy); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    gluPerspective(45.0, (float)sx/(float)sy, 1.0, 100.0); 
    glMatrixMode(GL_MODELVIEW); 

    glClearColor(0, 0, 0, 1); 
    glClearDepth(1.0); 
    glEnable(GL_DEPTH_TEST); 

    for (;;) { 
     if (!input()) break; 
     render(); 
     SDL_Delay(10); 
    } 

    SDL_FreeSurface(surf); 
    SDL_Quit(); 
    return 0; 
} 

Answer 1

在第一个代码块，改变你的glColor3b()呼叫glColor3ub()。或者传入127而不是255。

Answer 2

试试你SDL_SetVideoMode()调用之前设置一些GL attributes：

SDL_GL_SetAttribute(SDL_GL_RED_SIZE,  5); 
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 5); 
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5); 
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 5); 
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16); 
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); 

而且，通过在SDL_OPENGL，而不是SDL_HWSURFACE | SDL_DOUBLEBUF：

if (!(surf = SDL_SetVideoMode(sx, sy, bpp, SDL_OPENGL)))