camera.h

#ifndef CAMERA_H
#define CAMERA_H

#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>



// Default camera values
const float YAW = 0.0f;
const float PITCH = 7.0f;
const float SPEED = 2.5f;
const float SENSITIVITY = 0.1f;
const float ZOOM = 7.0f;


// An abstract camera class that processes input and calculates the corresponding Euler Angles, Vectors and Matrices for use in OpenGL
class Camera
{
public:
    // camera Attributes
    glm::vec3 Position;
    glm::vec3 Front;
    glm::vec3 Up;
    glm::vec3 WorldUp;
    // euler Angles
    float Yaw;
    float Pitch;
    // camera options
    float MovementSpeed;
    float MouseSensitivity;
    float Zoom;

    // constructor with vectors
    Camera(glm::vec3 position = glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3 up = glm::vec3(0.0f, 1.0f, 0.0f), float yaw = YAW, float pitch = PITCH) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM){
        this->Position = position;
        this->WorldUp = up;
        this->Yaw = yaw;
        this->Pitch = pitch;
        this->updateCameraVectors(0.0f);
    }
    // constructor with scalar values
    Camera(float posX, float posY, float posZ, float upX, float upY, float upZ, float yaw, float pitch) : Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM){
        this->Position = glm::vec3(posX, posY, posZ);
        this->WorldUp = glm::vec3(upX, upY, upZ);
        this->Yaw = yaw;
        this->Pitch = pitch;
        this->updateCameraVectors(0.0f);
    }

    // returns the view matrix calculated using Euler Angles and the LookAt Matrix
    glm::mat4 GetViewMatrix(){
        return glm::lookAt(this->Position, this->Position + this->Front, this->Up);
    }

    glm::mat4 GetProjectionMatrix(float fov=45.0, float ratio=1.0, float near=0.1, float far=5000.0){
        return glm::perspective(fov, ratio, near, far);
    }

    void updatePosition(glm::vec3 position){

        this->Position = position - Front * Zoom;
    }


    void ProcessKeyboardRotation(float YawRot, float PitchRot, float deltaTime, GLboolean constrainPitch = true)
    {
        float velocity = this->MovementSpeed * deltaTime;
        YawRot *= velocity;
        PitchRot *= velocity;

        this->Yaw += YawRot;
        this->Pitch += PitchRot;


        // Make sure that when pitch is out of bounds, screen doesn't get flipped
        if (constrainPitch)
        {
            if (this->Pitch > 89.0f)
                this->Pitch = 89.0f;
            if (this->Pitch < -89.0f)
                this->Pitch = -89.0f;
        }
    }

    // processes input received from a mouse input system. Expects the offset value in both the x and y direction.
    void ProcessMouseMovement(float xoffset, float yoffset, GLboolean constrainPitch = true){
        
	    ProcessKeyboardRotation(xoffset, yoffset, constrainPitch);
    }

    // processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
    void ProcessMouseScroll(float yoffset){
        Zoom -= (float)yoffset / 3.0f;
        if (Zoom < 1.0f)
            Zoom = 1.0f;
        if (Zoom > 45.0f)
            Zoom = 45.0f;
    }

    // calculates the front vector from the Camera's (updated) Euler Angles
    void updateCameraVectors(float planeYaw){
        float currYaw = planeYaw + Yaw;
        // calculate the new Front vector
        glm::vec3 front;
        front.x = cos(glm::radians(currYaw)) * cos(glm::radians(Pitch));
        front.y = sin(glm::radians(Pitch));
        front.z = sin(glm::radians(currYaw)) * cos(glm::radians(Pitch));
        Front = glm::normalize(front);
        // also re-calculate the Right and Up vector
        glm::vec3 right = glm::normalize(glm::cross(Front, WorldUp));  // normalize the vectors, because their length gets closer to 0 the more you look up or down which results in slower movement.
        Up = glm::normalize(glm::cross(right, Front));
    }
};

#endif