text: 
  /*
      pbrt source code is Copyright(c) 1998-2016
                          Matt Pharr, Greg Humphreys, and Wenzel Jakob.
  
      This file is part of pbrt.
  
      Redistribution and use in source and binary forms, with or without
      modification, are permitted provided that the following conditions are
      met:
  
      - Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
  
      - Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
  
      THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
      IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
      TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
      PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
   */
  
  #if defined(_MSC_VER)
  #define NOMINMAX
  #pragma once
  #endif
  
  #ifndef PBRT_CAMERAS_PERSPECTIVE_H
  #define PBRT_CAMERAS_PERSPECTIVE_H
  
  // cameras/perspective.h*
  #include "pbrt.h"
  #include "camera.h"
  #include "film.h"
  
  namespace pbrt
  {
  // PerspectiveCamera Declarations
  class PerspectiveCamera: public ProjectiveCamera
  {
  public:
      // PerspectiveCamera Public Methods
      PerspectiveCamera(const AnimatedTransform &CameraToWorld,
                        const Bounds2f &screenWindow, Float shutterOpen,
                        Float shutterClose, Float lensRadius, Float focalDistance,
                        Float fov, Film *film, const Medium *medium);
      Float GenerateRay(const CameraSample &sample, Ray *) const;
      Float GenerateRayDifferential(const CameraSample &sample,
                                    RayDifferential *ray) const;
      Spectrum We(const Ray &ray, Point2f *pRaster2 = nullptr) const;
      void Pdf_We(const Ray &ray, Float *pdfPos, Float *pdfDir) const;
      Spectrum Sample_Wi(const Interaction &ref, const Point2f &sample,
                         Vector3f *wi, Float *pdf, Point2f *pRaster,
                         VisibilityTester *vis) const;
  
  private:
      // PerspectiveCamera Private Data
      Vector3f dxCamera, dyCamera;
      Float A;
  };
  
  PerspectiveCamera *CreatePerspectiveCamera(const ParamSet &params,
                                             const AnimatedTransform &cam2world,
                                             Film *film, const Medium *medium);
  
  }  // namespace pbrt
  
  #endif  // PBRT_CAMERAS_PERSPECTIVE_H
  