content: # Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES.  All rights reserved.
  #
  # NVIDIA CORPORATION & AFFILIATES and its licensors retain all intellectual property
  # and proprietary rights in and to this software, related documentation
  # and any modifications thereto.  Any use, reproduction, disclosure or
  # distribution of this software and related documentation without an express
  # license agreement from NVIDIA CORPORATION & AFFILIATES is strictly prohibited.
  
  import torch
  from . import Camera
  import numpy as np
  
  
  def projection(x=0.1, n=1.0, f=50.0, near_plane=None):
      if near_plane is None:
          near_plane = n
      return np.array(
          [[n / x, 0, 0, 0],
           [0, n / -x, 0, 0],
           [0, 0, -(f + near_plane) / (f - near_plane), -(2 * f * near_plane) / (f - near_plane)],
           [0, 0, -1, 0]]).astype(np.float32)
  
  
  class PerspectiveCamera(Camera):
      def __init__(self, fovy=49.0, device='cuda'):
          super(PerspectiveCamera, self).__init__()
          self.device = device
          focal = np.tan(fovy / 180.0 * np.pi * 0.5)
          self.proj_mtx = torch.from_numpy(projection(x=focal, f=1000.0, n=1.0, near_plane=0.1)).to(self.device).unsqueeze(dim=0)
  
      def project(self, points_bxnx4):
          out = torch.matmul(
              points_bxnx4,
              torch.transpose(self.proj_mtx, 1, 2))
          return out
  