camera.h

#ifndef CAMERA_H
#define CAMERA_H

#include <glad/glad.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/ext.hpp>
#include <glm/gtx/string_cast.hpp>
#include <iostream>

#include <vector>

// Defines several possible options for camera movement. Used as an
// abstraction to stay away from window-system specific input methods
enum Camera_movement { FORWARD, BACKWARD, LEFT, RIGHT };

// Default camera values
const float YAW = -90.0f;
const float PITCH = 0.0f;
const float SPEED = 2.5f;
const float SENSITIVITY = 0.05f;
const float ZOOM = 45.0f;

// 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 Right;
  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) {
    Position = position;
    WorldUp = up;
    Yaw = yaw;
    Pitch = pitch;
    updateCameraVectors();
  }
  // 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) {
    Position = glm::vec3(posX, posY, posZ);
    WorldUp = glm::vec3(upX, upY, upZ);
    Yaw = yaw;
    Pitch = pitch;
    updateCameraVectors();
  }

  glm::mat4 mylookAt(glm::vec3 position, glm::vec3 target, glm::vec3 worldUp) {

    // 1. Position = known
    // 2. Calculate cmaeraDirection
    glm::vec3 zaxis = glm::normalize(position - target);
    // 3. Get positive right axis vector
    glm::vec3 xaxis = glm::normalize(glm::cross(glm::normalize(worldUp), zaxis));
    // 4. Calculate camera up vector
    glm::vec3 yaxis = glm::cross(zaxis, xaxis);

    // Create translation and rotation matrix
    // In glm, we access elements as mat[col][row] due to column-major
    // layout
    glm::mat4 translation = glm::mat4(1.0f);
    translation[3][0] = -position.x; // Third column, first row
    translation[3][1] = -position.y;
    translation[3][2] = -position.z;

    glm::mat4 rotation = glm::mat4(1.0f);
    rotation[0][0] = xaxis.x; // First column, first row
    rotation[1][0] = xaxis.y;
    rotation[2][0] = xaxis.z;
    rotation[0][1] = yaxis.x; // First column, second row
    rotation[1][1] = yaxis.y;
    rotation[2][1] = yaxis.z;
    rotation[0][2] = zaxis.x; // First column, third row
    rotation[1][2] = zaxis.y;
    rotation[2][2] = zaxis.z;

    // Return lookAt matrix as combination of translation and rotation matrix
    return rotation * translation; // Remember to read from right to left (first
                                   // translation then rotation)
  }

  glm::mat4 GetViewMatrix() {
     return mylookAt(Position, Position + Front, Up);
     //return glm::lookAt(Position, Position + Front, Up);
  }

  void ProcessKeyboard(Camera_movement direction, float deltaTime) {
    float velocity = MovementSpeed * deltaTime;
    if (direction == FORWARD)
      Position += Front * velocity;
    if (direction == BACKWARD)
      Position -= Front * velocity;
    if (direction == LEFT)
      Position -= Right * velocity;
    if (direction == RIGHT)
      Position += Right * velocity;

    Position.y = 0.0f; // Constrain to x-z plane
  }

  // 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) {
    xoffset *= MouseSensitivity;
    yoffset *= MouseSensitivity;

    Yaw += xoffset;
    Pitch += yoffset;

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

    // Update Front, Right and Up Vectors using the updated Euler angles
    updateCameraVectors();
  }

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

private:
  // Calculates the front vector from the Camera's (updated) Euler Angles
  void updateCameraVectors() {
    // Calculate the new Front vector
    glm::vec3 front;
    front.x = cos(glm::radians(Yaw)) * cos(glm::radians(Pitch));
    front.y = sin(glm::radians(Pitch));
    front.z = sin(glm::radians(Yaw)) * cos(glm::radians(Pitch));
    Front = glm::normalize(front);
    // Also re-calculate the Right and Up vector
    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