Free look and custom pivot orbit camera implementation

ImprovedCamera.hpp

#include <as/as-math-ops.hpp> // https://github.com/pr0g/as

struct Camera
{
  as::vec3 pivot = as::vec3::zero(); // pivot point to rotate about
  as::vec3 offset = as::vec3::zero(); // offset relative to pivot
  float yaw = 0.0f; // yaw rotation in radians
  float pitch = 0.0f; // pitch rotation in radians

  // view camera transform (v in MVP)
  as::affine view() const;
  // world camera transform
  as::affine transform() const;
};

inline as::affine Camera::view() const
{
  return as::affine_inverse(transform());
}

inline as::affine Camera::transform() const
{
  // multiplication order left to right
  return as::affine_mul(
    as::affine_mul(
      as::affine_from_vec3(offset), as::affine_from_mat3(as::mat3_rotation_zxy(
                                      pitch, yaw, 0.0f))),
    as::affine_from_vec3(pivot));
}

// see https://github.com/pr0g/as-camera/blob/0ed6ea8284bede968d20392b792d35ad6d33c3bc/include/as-camera/as-camera.hpp
// for a more complete implementation