Question

I was setting up a camera following this tutorial. My problem is that when I move it isn’t fluid, it kinda jumps. I’m calculating the MVP whenever the mouse moves using this code:

void motion(int x, int y) {
    static bool wrap = false;

    if(!wrap) {
        int ww = glutGet(GLUT_WINDOW_WIDTH);
        int wh = glutGet(GLUT_WINDOW_HEIGHT);

        int dx = x - ww / 2;
        int dy = y - wh / 2;

        const float mousespeed = 0.001;

        angles.x += dx * mousespeed;
        angles.y += dy * mousespeed;


        if(angles.x < -M_PI)
            angles.x += M_PI * 2;
        else if(angles.x > M_PI)
            angles.x -= M_PI * 2;

        if(angles.y < -M_PI / 2)
            angles.y = -M_PI / 2;
        if(angles.y > M_PI / 2)
            angles.y = M_PI / 2;

        lookat.x = sinf(angles.x) * cosf(angles.y);
        lookat.y = sinf(angles.y);
        lookat.z = cosf(angles.x) * cosf(angles.y);
        view = glm::lookAt(position, position + lookat, glm::vec3(0, 1, 0));

        // move mouse pointer back to the center of the window
        wrap = true;
        glutWarpPointer(ww / 2, wh / 2);
    } else {
        wrap = false;
    }
}

And then I’m updating the attribute on my ‘OnIdele()’ function:

void onIdle() {
    glUseProgram(program);

    glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
    glm::mat4 Model = glm::mat4(1.0f);
    glm::mat4 MVP = Projection * view * Model;

    glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, glm::value_ptr(MVP));

    glutPostRedisplay();
}

My question is, is this the right way to implement this? Is there any way to avoid the laggyness?

Also if you don’t mind me asking, how exactly does this code work? I know it limits where you can look but I can’t seem to make sense of it:

 if(angles.x < -M_PI)
            angles.x += M_PI * 2;
        else if(angles.x > M_PI)
            angles.x -= M_PI * 2;

        if(angles.y < -M_PI / 2)
            angles.y = -M_PI / 2;
        if(angles.y > M_PI / 2)
            angles.y = M_PI / 2;

Answer 1

See if increasing mousespeed makes a difference. After you find the distance the mouse has moved, stored in dx and dy, you scale the distance by mousespeed before adding it to the camera’s angles. The lower the value of mousespeed the less your mouse movement will affect the angles of your camera, and vice versa.

Also the code you asked about is limiting your camera angles to between 0 and PI * 2, or 0 and 360 degrees.