;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10; Package: photo -*-
;;;; *************************************************************************
;;;; FILE IDENTIFICATION
;;;;
;;;; Name:          fov.lisp
;;;; Purpose:       Field of view functions for cl-photo
;;;; Programmer:    Kevin M. Rosenberg
;;;; Date Started:  April 2005
;;;;
;;;; $Id$
;;;;
;;;; This file, part of cl-photo, is Copyright (c) 2005 by Kevin Rosenberg.
;;;; Rights of modification and redistribution are in the LICENSE file.
;;;;
;;;; *************************************************************************

(in-package #:photo)

(defun fov-one-dim (focal-length frame-size 
                                 &key (projection :rectilinear))
  (ecase projection
    (:rectilinear
     (radians->degrees (* 2 (atan (/ frame-size 2 focal-length)))))
    (:equisolid 
     (radians->degrees (* 4 (asin (/ frame-size 4 focal-length)))))
    (:equidistance 
     (radians->degrees (/ (* 2 frame-size) focal-length)))
    (:orthogonal
     (radians->degrees (* 2 (asin (/ frame-size 2 focal-length)))))
    (:stereographic
     (radians->degrees (* 4 (atan (/ frame-size 4 focal-length)))))
    ))
    
  
(defun fov (focal-length frame-width frame-height
                         &key (projection :rectilinear))
  "Returns the angle of field of view for a focal length and frame size at infinity"
  (values
   (fov-one-dim focal-length frame-width :projection projection)
   (fov-one-dim focal-length frame-height :projection projection)
   (fov-one-dim focal-length (diagonal frame-width frame-height)
                :projection projection)))

(defun fov-distance (focal-length frame-width frame-height distance
                                  &key (projection :rectilinear))
  "Returns the field of view and image magnificaion ratio at a given distance.
NOTE: magnification assumes that distance is in the same units as frame size: mm"
  (multiple-value-bind (fov-width fov-height fov-diagonal)
      (fov focal-length frame-width frame-height :projection projection)
    (let* ((d-width (* distance (sin (degrees->radians fov-width))))
           (d-height (* distance (sin (degrees->radians fov-height))))
           (d-diagonal (* distance (sin (degrees->radians fov-diagonal))))
           (mag (/ frame-width d-width))) 
      (values d-width d-height d-diagonal mag))))

(defun fov-format (focal-length format &key (projection :rectilinear))
  "Returns the angle of field of view for a focal length and frame size at infinity"
  (let ((dim (format-dimensions format))) 
    (fov focal-length (car dim) (cdr dim) :projection projection)))