Name: flight_path
  
   Author: Ian Curington, Advanced Visual Systems, Inc
  
   Type: Data Input
  
   Language: C
  
   Description:
   -----------
   The Flight Path Module
   takes a scatter field position list and animates the camera
   path along the trajectory.
   Derived from camera.c in /usr/avs/examples.
   The scatter path field is in the form of
   "field 1D 3-space irregular float"
   where the coordinate information in the field
   specifies the path. The data values are ignored.
   It moves %top, not the camera, so multiple
   camera views can be set up to watch the path.
   The file_descriptor or read_field modules can be used to
   get the path from an external file.
   Animated Integer can be used to control time, for a
   moving sequence.
  
   Inputs: Scatter Field
  
   Outputs: Geometry edit list with Transform control matrix
  
   Parameters:
         Up      string with 3x floats, for up vector
         FOV     field of view angle in degrees
         Time    integer dial for time sample along path
         Offset  string with 3x floats, for global offset vector
  
  
   Notes:
   -----
   This module demonstrates the use of the routine: GEOMedit_set_matrix
   on %top in the geometry viewer
   to define the flight_path projection.  This module allows you to specify 
   a camera position using the following parameters:
     from the path:
  	from: 	A point that defines the position of the camera
  	at:	A point that the camera is looking at - used with from to 
  	        defined the camera direction only
     from controls:
  	up: 	A vector that defines the "up" direction of the flight_path
   	FOV: 	The angle defining the frustrum of the camera in degrees