// Copyright 2024 Bytedance Inc. All Rights Reserved.
// Author: tianlei.richard@qq.com (tianlei.richard)

#include "camera.h"

Camera::Camera(const Vector3d &up)
    : position_(Point3d::Identity()), gaze_(Vector3d::Identity()), up_(up) {}

TransformMatrix Camera::get_view_transform() const {
  // Move camera to origin
  TransformMatrix m{{1, 0, 0, -position_.x()},
                    {0, 1, 0, -position_.y()},
                    {0, 0, 1, -position_.z()},
                    {0, 0, 0, 1}};
  // Adjust to fit xyz
  const Vector3d &x_camera{(gaze_.cross(up_)).normalized()};
  m = TransformMatrix{{x_camera.x(), x_camera.y(), x_camera.z(), 0},
                      {up_.x(), up_.y(), up_.z(), 0},
                      {-gaze_.x(), -gaze_.y(), -gaze_.z(), 0},
                      {0, 0, 0, 1}} *
      m;

  return m;
}