Creating a First Person camera in Open GL 2.0 and glm - c++

Question

I am farly new to Open GL, and c++ and have come across the issue of creating a first person camera. I don't understand matrix math so that makes it all the more harder for me. So far, for calculating the rotation of the camera I have gone for this:
void CameraFP::calculate_view() {
m_view = glm::rotate(m_view, this->get_rotation_x(), glm::vec3(1, 0, 0));
m_view = glm::rotate(m_view, this->get_rotation_y(), glm::vec3(0, 1, 0));
}
That function is called every update call.
For handling the rotation of the camera via the mous, I've done the following:
void CameraFP::process_mouse(sf::Window *app) {
GLfloat mouse_x = app->GetInput().GetMouseX();
GLfloat mouse_y = app->GetInput().GetMouseY();
GLfloat mouse_x_delta = std::max(mouse_x, old_mouse_x) - std::min(mouse_x, old_mouse_x);
GLfloat mouse_y_delta = std::max(mouse_y, old_mouse_y) - std::min(mouse_y, old_mouse_y);
y_rot += mouse_x_delta / (float)app->GetWidth();
x_rot += mouse_y_delta / (float)app->GetHeight();
this->old_mouse_x = mouse_x;
this->old_mouse_y = mouse_y;
app->SetCursorPosition(app->GetWidth() / 2, app->GetHeight() / 2);
}
and for handling the movement I've done the following:
void CameraFP::process_keyboard(sf::Window *app) {
const sf::Input *input = &app->GetInput();
if (input->IsKeyDown(sf::Key::W)) {
position.z += 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::S)) {
position.z -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::A)) {
position.x -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::D)) {
position.x += 1.0f / 100.0f;
}
}
My issues lie in the fact that my camera does not move in the direction you face, and that it never stops rotating :/. Also, if you could point me to a guide or something on Matrix math that would be awesome :)
Edit 2:'
I just started a new process mouse function, and it a movement along the x axis of the screen as a y rotation for the camera correctly. However, it doesn't matter if I move the mouse left or right, both movements rotate me right. Same with the x axis in 3d space, but this happens downwards. Any ideas on what is causing this?
void CameraFP::process_mouse(sf::Window *app) {
GLfloat mouse_x = app->GetInput().GetMouseX();
GLfloat mouse_y = app->GetInput().GetMouseY();
GLfloat mouse_x_delta = old_mouse_x - mouse_x;
GLfloat mouse_y_delta = old_mouse_y - mouse_y;
if (mouse_x_delta > 0) {
y_rot += mouse_x_delta / (float)app->GetWidth() * 0.1f;
} else if (mouse_x_delta < 0) {
y_rot -= mouse_x_delta / (float)app->GetWidth() * 0.1f;
}
if (mouse_y_delta > 0) {
x_rot += mouse_y_delta / (float)app->GetWidth() * 0.1f;
} else if (mouse_y_delta < 0) {
x_rot -= mouse_y_delta / (float)app->GetWidth() * 0.1f;
}
if (mouse_x != old_mouse_x) {
m_view = glm::rotate(m_view, y_rot, glm::vec3(0, 1, 0));
}
if (mouse_y != old_mouse_y) {
m_view = glm::rotate(m_view, x_rot, glm::vec3(1, 0, 0));
}
this->old_mouse_x = mouse_x;
this->old_mouse_y = mouse_y;
app->SetCursorPosition(app->GetWidth() / 2, app->GetHeight() / 2);
}

Answer 1

I don't have time to look for my camera code at the moment, but what I can tell you right now is, that your movement calculation is simply wrong. You aren't taking the camera rotation into account.
You have to do something like this:
if (input->IsKeyDown(sf::Key::W)) {
position.z += sin(camera_rot_y);
}
else if (input->IsKeyDown(sf::Key::S)) {
position.z -= sin(camera_rot_y);
}
if (input->IsKeyDown(sf::Key::A)) {
position.x -= cos(camera_rot_y);
}
else if (input->IsKeyDown(sf::Key::D)) {
position.x += cos(camera_rot_y);
}
Also you can use "else if"s, because you cannot move forward and backward at the same time.^^
Also, why are you using std::min() and max() in the following code?:
GLfloat mouse_x_delta = std::max(mouse_x, old_mouse_x) - std::min(mouse_x, old_mouse_x);
GLfloat mouse_y_delta = std::max(mouse_y, old_mouse_y) - std::min(mouse_y, old_mouse_y);
If you want to rotate in the opposite direction you need to get a negative delta, which is impossible with your code. Get rid of the min() and max() functions.
BTW: My camera code is not the most efficient (uses rotate instead of direct calculations), but it works.

Answer 2

You didn't show usage of position in CameraFP and m_view but I think problem si here:
void CameraFP::process_keyboard(sf::Window *app) {
const sf::Input *input = &app->GetInput();
if (input->IsKeyDown(sf::Key::W)) {
position.z += 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::S)) {
position.z -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::A)) {
position.x -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::D)) {
position.x += 1.0f / 100.0f;
}
}
You must multiply matrix, with this translation, and m_view. In matrix multiplication is important order of matrices. First must be m_view because it is main matrix, and you want move forward from m_view rotation. But there is glm namespace and there is method glm::translate which them multiply in right order and you just create glm::vec3 as parameter of that method (translation with x, y, z).
(If you use relative position ... only difference between frames)
So you must change it like this:
void CameraFP::process_keyboard(sf::Window *app) {
const sf::Input *input = &app->GetInput();
glm::vec3 pos;
if (input->IsKeyDown(sf::Key::W)) {
pos.z += 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::S)) {
pos.z -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::A)) {
pos.x -= 1.0f / 100.0f;
}
if (input->IsKeyDown(sf::Key::D)) {
pos.x += 1.0f / 100.0f;
}
//Make translation
m_view = glm::translate(m_view, pos);
//Values at position 12, 13, 14 are translation x, y, z
//Save absolute position of camera
position = glm::vec3(m_view[12], m_view[13], m_view[14]);
}
PS: Sorry for my poor english.