#if ( frame_number != 0 & frame_number != 1 )
  #fopen Previous "data.txt" read
  #read ( Previous , Position , Velocity )
  #fclose Previous
#else
  #declare Position = < -45 , 40 , 5 > ;  
  #declare Velocity = < 5 , 1 , 5 > ;     
#end

//draw something and move it
//folowing physics laws

#fopen Previous "data.txt" write

#write ( Previous , Position , "," , Velocity , "\n" )

#fclose Previous