Tidal bulges model - WORK IN PROGRESS

globals [ state px py vix viy earth themoon grav embarycenter]

breed [ earths anearth ]
breed [ moons moon ]
breed [ vectors vector ]
breed [ waters water ]
breed [ barycenters barycenter]
breed [ gravitations gravitation ]

turtles-own [ 
  mass    ; mass
  vx      ; velocity x
  vy      ; velocity y
  ax      ; tick acceleration x
  ay      ; tick accelration y 
  ]

to setup
  ;; (for this model to work with NetLogo's new plotting features,
  ;; __clear-all-and-reset-ticks should be replaced with clear-all at
  ;; the beginning of your setup procedure and reset-ticks at the end
  ;; of the procedure.)
  __clear-all-and-reset-ticks
  set-default-shape turtles "circle"


  create-gravitations 1
  [
    set hidden? true
  ]

  create-moons 1
  [
    set size 5
    set mass moon-mass
    ;; sets initial position
    setxy 15 100
    ;; sets initial velocity x y
    set vy -2
    set vx 3.5
    ;; moon's white, but this looks better
    set color gray
  ]

  create-earths 1 
  [
    ; inits earth
    set size 20
    set mass earth-mass
    setxy 0 0 
    set color green
    set vx .1

  ]
;  create-waters 1440
  create-waters 180
  [

  ]
  create-barycenters 1 [
    set hidden? true
  ]
  
;  ask one-of barycenters [
;    move-barycenter
;  ]  
  
  
      
    set themoon one-of moons
    set earth one-of earths
    set grav one-of gravitations
    set embarycenter one-of barycenters
  
  
  layout-circle waters 10

ask waters 
    [
      set color blue
      set size 1
      set vx [vx] of earth
      set vy [vy] of earth
      set mass .5
    ]
    
    
  
  ;; follow earth at first
  ;;follow one-of earths  
end 

to go

  
  ;; first clear old acceleration variables
  ask turtles [set ax 0 set ay 0]
  ;; then calculate new acceleration to all turtls
  ask earths [ calc-earth-acceleration ]
  ask waters [ calc-waters-acceleration ]
  ;ask waters [ earth-push-water ]
  ask moons [ calc-moon-acceleration ]
  ;; then change their velocities according to acceleration
  ask turtles [ add-acceleration ]
  ;; then move them
  ask turtles [ move ]
  ;; set the gravitational center between moon and earth
  ask earths [find-center]
  
  ask waters [add-friction]
  
  tick
end 

to find-center
  let d distance themoon
  let h towards themoon
  let reldistance d * [mass] of themoon / (mass + [mass] of themoon)
;  let reldistance [mass] of amoon / (mass + [mass] of amoon)
  ask barycenters [setxy ([xcor] of myself + sin(h) * reldistance) ([ycor] of myself + cos(h) * reldistance)]
end 

to calc-earth-acceleration

  let d distance themoon
  let h towards themoon
  let relativegravity [mass] of themoon / ([mass] of themoon + [mass] of self)
  let force ([mass] of self + [mass] of themoon) / d ^ 2 
;  show force
  set ax force * sin h * relativegravity
  set ay force * cos h * relativegravity

;; adding this accelration to waters too

  ask waters [
    set ax ax + force * sin h * relativegravity
    set ay ay + force * cos h * relativegravity
  ]
end 

to calc-moon-acceleration
  let d distance earth
  let h towards earth
  let relativegravity [mass] of earth / ([mass] of earth + [mass] of self)
  let force ([mass] of self * [mass] of earth) / d ^ 2   
;  show force
  
  set ax force * sin h * relativegravity
  set ay force * cos h * relativegravity
end 

to calc-waters-acceleration
  ; find heading towards earth
  let h towards earth
  ; reverse it
  set h h - 180
  ; place gravation at radius of earth away from earth
  ask grav [setxy ([xcor] of earth + sin h * 10) ([ycor] of earth + cos h * 10)]
  
  ;; if water is already exactly on surface of earth, no acceleration
   ifelse (xcor = [xcor] of grav and ycor = [ycor] of grav)
    [
      set ax ay
      set ay ax
    ]
    ;; if water is "below earth's surface", pull it towards grav
   [
   ifelse (towards earth != towards grav)
    [
      ; now pull water towards grav
      set h towards grav
      ; find distance to grav
      let d distance grav
      ; the closer it is, the less it pulls or pushes
      
      let force d / 8
      set ax force * sin h
      set ay force * cos h

    ]
    ;; if water is above earth's surface, pull it towards grav by a bit less
    [
      ; now pull water towards grav
      set h towards grav
      ; find distance to grav
      let d distance grav
      ; the closer it is, the less it pulls or pushes
      
      let force d / 10
      set ax force * sin h
      set ay force * cos h
;      
    ]
    
   ]
   
  ; now for gravity between water and moon
  ; first moon pulls water
  let d distance themoon
  set h towards themoon
;  let relativegravity [mass] of themoon / ([mass] of themoon + [mass] of self)
  let relativegravity 1
  let force .03
;  let force ([mass] of self * [mass] of themoon) / d ^ 2   
  set ax ax + force * sin h * relativegravity
  set ay ay + force * cos h * relativegravity
  ; then water pulls moon 
  ask themoon [
    set ax ax + force * sin (h - 180) * relativegravity
    set ay ay + force * cos (h - 180) * relativegravity
  ]
  

  
  ; add push between waters
    ask waters with [who != [who] of myself and xcor != [xcor] of myself and ycor != [ycor] of myself]
    [
      if distance myself < 3
      [
        set h towards myself
        set force wpush / distance myself
        set ax ax + force * sin (h - 180)
        set ay ay + force * cos (h - 180)
        ]

    ]
end 

to add-friction
  
  set vx vx * friction
  set vy vy * friction
end 

to add-acceleration
  set vx vx + ax
  set vy vy + ay
end 

to move
  setxy xcor + vx ycor + vy
end 

to earth-push-water
  let d distance earth
  let h towards earth + 180
  let force ([mass] of self * [mass] of earth) / d ^ 2
 ; show force
;  show force
  set ax ax + force * sin h / [mass] of self
  set ay ay + force * cos h / [mass] of self
end