CODEWITHSUNDEEP
c++opengl
matthew3r
matthew3r

Reputation: 692

c++ - OpenGL movement with deltatime

So, I started programming again in C++ and trying things out with OpenGL. Currently I have a basic application where I just want to move the camera with keys. I read many article about this, but still I have problem with the movement, I guess because even if only a little, but they differs from my program. First I made a 60 fps limit and calculated the speed with deltatime, but the movement was laggy. Now I turned off FPS limiting, but now it runs at around 4000 FPS, so deltatime is most of the time 0 or 1, so the movement is really really slow. I'm sure I don't understand something about the concept, but I need to point it out.

The main loop:

while (running) {
    if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {

        if (msg.message == WM_QUIT) {
            running = false;

            break;
        } else {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    } else {
        clock_t last = clock();
        deltaTime = last-start;

        //if ((double)deltaTime >= 16.666666666) {
        fps++;
        millis += deltaTime;
        start = last;

        if (millis > 1000) {
            millis = 0;
            std::cout << "FPS: " << fps << std::endl;
            fps = 0;
        }

        openglContext.renderScene();
        //}
    }
}

WndProc key handler:

float speed = 5.0f;

...

case WM_KEYDOWN:
    switch(wParam) {
        case 0x57:
            openglContext.updateCoordinates(0.0f, 0.0f, ((float)deltaTime / 1000.0f * speed), glm::radians(angle));
            break;
    }
    break;

I know it's not perfect, but as I wrote before I tried many "solutions". Hope someone can help. Thanks in advance!

Solution:

There is still many to do, but for now it's perfect.

LARGE_INTEGER start;
LARGE_INTEGER frequency;
QueryPerformanceFrequency(&frequency);
QueryPerformanceCounter(&start);

while (running) {

    ...

        LARGE_INTEGER current;
        QueryPerformanceCounter(&current);
        dt = ((double)(current.QuadPart - start.QuadPart) / (double)frequency.QuadPart);
        QueryPerformanceCounter(&start);

        ... key handling
        ... render
        ...

Upvotes: 1

Views: 2951

Answers (1)

BDL
BDL

Reputation: 22170

The problem that delta_time is either 0 or 1 happens because of the generally low resolution of std::clock(). In most cases, the minimal time that can be measured is around 0.01 seconds, which is way to less for a rendering application. Reference

Depending on your system and on the compiler used, there are several alternatives that will allow you to measure timings with higher precision.

Upvotes: 1

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