It's a long post so I might not answer everything. I think it is most likely precision issue. Lets start with the camera rotation problem. I think the main problem is here
view_matrix = glm::lookAt(
cameraPosition,
cameraPosition+directionVector,
upVector);
As you said, position is quite a big number like 2.9657e+006 - and look what glm does in glm::lookAt:
GLM_FUNC_QUALIFIER detail::tmat4x4<T> lookAt
(
detail::tvec3<T> const & eye,
detail::tvec3<T> const & center,
detail::tvec3<T> const & up
)
{
detail::tvec3<T> f = normalize(center - eye);
detail::tvec3<T> u = normalize(up);
detail::tvec3<T> s = normalize(cross(f, u));
u = cross(s, f);
In your case, eye and center are these big (very similar) numbers and then glm subtracts them to compute f. This is bad, because if you subtract two almost equal floats, the most significant digits are set to zero, which leaves you with the insignificant (most erroneous) digits. And you use this for further computations, which only emphasizes the error. Check this link for some details.
The z-fighting is similar issue. Z-buffer is not linear, it has the best resolution near the camera because of the perspective divide. The z-buffer range is set according to your near and far clipping plane values. You always want to have the smallest possible ration between far and near values (generally far/near should not be greater than 30000). There is a very good explanation of this on the openGL wiki, I suggest you read it :)
Back to the camera issue - first, I would consider if you really need such a huge scene. I don't think so, but if yes, you could try computing your view matrix differently, compute rotation and translation separately, which could help your case. The way I usually handle camera:
glm::vec3 cameraPos;
glm::vec3 cameraRot;
glm::vec3 cameraPosLag;
glm::vec3 cameraRotLag;
int ox, oy;
const float inertia = 0.08f; //mouse inertia
const float rotateSpeed = 0.2f; //mouse rotate speed (sensitivity)
const float walkSpeed = 0.25f; //walking speed (wasd)
void updateCameraViewMatrix() {
//camera inertia
cameraPosLag += (cameraPos - cameraPosLag) * inertia;
cameraRotLag += (cameraRot - cameraRotLag) * inertia;
// view transform
g_CameraViewMatrix = glm::rotate(glm::mat4(1.0f), cameraRotLag[0], glm::vec3(1.0, 0.0, 0.0));
g_CameraViewMatrix = glm::rotate(g_CameraViewMatrix, cameraRotLag[1], glm::vec3(0.0, 1.0, 0.0));
g_CameraViewMatrix = glm::translate(g_CameraViewMatrix, cameraPosLag);
}
void mousePositionChanged(int x, int y) {
float dx, dy;
dx = (float) (x - ox);
dy = (float) (y - oy);
ox = x;
oy = y;
if (mouseRotationEnabled) {
cameraRot[0] += dy * rotateSpeed;
cameraRot[1] += dx * rotateSpeed;
}
}
void keyboardAction(int key, int action) {
switch (key) {
case 'S':// backwards
cameraPos[0] -= g_CameraViewMatrix[0][2] * walkSpeed;
cameraPos[1] -= g_CameraViewMatrix[1][2] * walkSpeed;
cameraPos[2] -= g_CameraViewMatrix[2][2] * walkSpeed;
break;
...
}
}
This way, the position would not affect your rotation. I should add that I adapted this code from NVIDIA CUDA samples v5.0 (Smoke Particles), I really like it :)
Hope at least some of this helps.