I am new here, I am now trying to render two images as fast as I can, so I used a teapot in OpenGL, and switching its color between green and purple in an idle function. My display card is Nvidia Geforce 310 and I have a CRT monitor(works at 75Hz) and DLP projector(works at 120Hz) connected to it.
When I put the render window in CRT(with Vsync on), the refresh rate is about 60Hz, I can see the flashing between green and purple. When I put the render window in projector(with Vsync on), the refresh rate is about 100Hz, and I can only see a white teapot(which is the sum of the green and purple).
1. Can anybody tell me for each image(either green or purple teapot) what is the refresh rate? Is that just the (total refresh rate)/2?
2. I want to use my camera to capture either one of the teapot, so I tried to use PGR firefly and run it at 60Hz fps, but it can't distinguish the green and purple, instead it sees the same thing as me, white teapot. Why?
3. I guess maybe it's because the camera and projector are not synchronized. I searched the forum, some people say I need a Quadro card them the interval between the green and purple is stable, then I can use that interval to sync camera
and projector. I wonder if I can do this without Quadro card?
4. It is said that when the fps is higher than human's flicker fusion frequency(75Hz), we will not see the flashing. But my CRT refresh rate is 75Hz, why can I still see the flashing?
Here's my code, I calculate OpenGL fps using QueryPerformanceCounter.
using namespace std;
double PCFreq = 0.0;
__int64 CounterStart = 0;
cout << "QueryPerformanceFrequency failed!\n";
PCFreq = double(li.QuadPart)/1000.0;
CounterStart = li.QuadPart;
static int count;
static double save;
static clock_t last, current;
if( count <= 100 )
count = 0;
last = current;
current = clock();
timegap = (current-last)/(GetCounter()*1000000);
save = 100.0/timegap;
double FPS = CalFrequency();
printf("FPS = %f\n", FPS);
glutSwapBuffers(); // for GLUT_DOUBLE
//glFlush();// for GLUT_SINGLE
int main(int argc, char *argv)
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
//glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
You can test my code to see if there's something wrong.