SDL+OpenGL app: blank screen
- by Lococo
I spent the last three days trying to create a small app using SDL + OpenGL. The app itself runs fine -- except it never outputs any graphics; just a black screen.
I've condensed it down to a minimal C file, and I'm hoping someone can give me some guidance. I'm running out of ideas.
I'm using Windows Vista, MinGW & MSYS. Thanks in advance for any advice!
#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);
}
UPDATE: I have a version that works, but it changes orthographic to perspective. I'm not sure why this works and the other doesn't, but for future reference, here's a version that works:
#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;
}
