Camera Translation in OpenGL - opengl

Question

I am trying to do a class to walk through the world in OpenGL, but I am having problems with the mathematics. My idea here is to use the function lookAt from glm to set the observer in the position I wanted, and then just operate with the points that I pass to the function.
I think the functions to do rotations that I made are correct, but the translation part in the walk method seems to be wrong, and when I try to walk in the world if I just translate, or just rotated, things go right, but when I do both things just get messed.
here is the class so far:
#ifndef OBSERVER_H
#define OBSERVER_H
#include <GL/gl.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
class Observer {
private:
glm::vec3 eye, center, upp;
public:
glm::mat4 view;
Observer() {}
~Observer() {}
void initialize(glm::vec3 eye, glm::vec3 center, glm::vec3 upp);
void walk(GLfloat distance);
void pitch(GLfloat pitch);
void yaw(GLfloat yaw);
void roll(GLfloat roll);
void setView();
};
void Observer::initialize(glm::vec3 eye, glm::vec3 center, glm::vec3 upp)
{
this->eye = eye;
this->center = center;
this->upp = upp;
}
void Observer::walk(GLfloat distance)
{
glm::vec3 vector = glm::normalize(center - eye);
glm::vec3 translate = vector*distance - vector;
eye += translate;
center += translate;
upp += translate;
}
void Observer::roll(GLfloat roll) {
glm::mat4 rotate(1.0f);
rotate = glm::rotate(rotate, roll, glm::vec3(center - eye));
center = glm::vec3(rotate * glm::vec4(center, 1.0f));
upp = glm::vec3(rotate * glm::vec4(upp, 1.0f));
}
void Observer::yaw(GLfloat yaw) {
glm::mat4 rotate(1.0f);
rotate = glm::rotate(rotate, yaw, glm::vec3(upp - eye));
center = glm::vec3(rotate * glm::vec4(center, 1.0f));
upp = glm::vec3(rotate * glm::vec4(upp, 1.0f));
}
void Observer::pitch(GLfloat pitch) {
glm::mat4 rotate(1.0f);
glm::vec3 cross = glm::cross(center - eye, upp - eye);
rotate = glm::rotate(rotate, pitch, cross);
center = glm::vec3(rotate * glm::vec4(center, 1.0f));
upp = glm::vec3(rotate * glm::vec4(upp, 1.0f));
}
void Observer::setView()
{
view = glm::lookAt(eye, center, upp);
}
#endif
So right before I starting draw things I set the view matrix with this class in other part in the program. Can someone tell me if my maths are right?

Answer 1

When you walk, you only want to transform the eye and center position, not the upp vector. Just remove the upp += translate; line.