From 49116785ae43a466600a8353ba8a4ba01888c77b Mon Sep 17 00:00:00 2001
From: Dimitri Lozeve <dimitri.lozeve@gmail.com>
Date: Tue, 25 Jul 2017 23:38:11 +0200
Subject: [PATCH] Generate random bodies

---
 app/Main.hs | 47 +++++++++++++++++++++++++++++++++++++++--------
 orbit.cabal |  1 +
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/app/Main.hs b/app/Main.hs
index 05ac5c1..c8fcfe7 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -5,9 +5,38 @@ import Lib
 import Linear.Affine
 import Linear.V3
 
+import System.Random
+import Control.Monad (replicateM)
+
 import Graphics.Gloss hiding (Point)
 
 
+--------------------------------------------------------------------------------
+-- Random body generation
+--------------------------------------------------------------------------------
+
+randomBody :: IO Body
+randomBody = do
+  r <- randomIO :: IO Double
+  m <- randomIO :: IO Double
+  x <- randomIO :: IO Double
+  y <- randomIO :: IO Double
+  z <- randomIO :: IO Double
+  vx <- randomIO :: IO Double
+  vy <- randomIO :: IO Double
+  vz <- randomIO :: IO Double
+  -- Make radius proportional to mass for visualization
+  let radius = 20 * m
+  -- Scale mass
+  let mass = 1e3 * m
+  -- Scale position and speed
+  let posx = 1e3 * (2*x - 1)
+  let posy = 1e3 * (2*y - 1)
+  let speedx = 5e-5 * vx
+  let speedy = 5e-5 * vy
+  return $ Body "random" radius mass (P $ V3 posx posy 0) (V3 speedx speedy 0)
+
+
 --------------------------------------------------------------------------------
 -- CSV export
 --------------------------------------------------------------------------------
@@ -44,7 +73,7 @@ window :: Display
 window = InWindow "Orbit" (width, height) (offset, offset)
 
 displayBody :: Body -> Picture
-displayBody b = translate (realToFrac x/1e9) (realToFrac y/1e9) $ circle (realToFrac (bodyRadius b)/1e8)
+displayBody b = translate (realToFrac x) (realToFrac y) $ circle (realToFrac (bodyRadius b))
   where P (V3 x y _) = bodyPosition b
 
 displayBodies :: [Body] -> Picture
@@ -54,13 +83,15 @@ drawing :: Picture
 drawing = color white $ circle 80
 
 main :: IO ()
-main = simulate
-  window
-  black
-  25
-  [sun, earth, moon, mercury, venus, mars]
-  displayBodies
-  (\_ dt bs -> updateAll (realToFrac dt*1e6) bs)
+main = do
+  bodies <- replicateM 300 randomBody
+  simulate
+    window
+    black
+    25
+    bodies
+    displayBodies
+    (\_ dt bs -> updateAll (realToFrac dt*1e6) bs)
 
 --main :: IO ()
 --main = steps 1000000 10 [sun, earth, moon, mercury, venus, mars]
diff --git a/orbit.cabal b/orbit.cabal
index eed3753..07d3961 100644
--- a/orbit.cabal
+++ b/orbit.cabal
@@ -27,6 +27,7 @@ executable orbit-exe
   build-depends:       base
                      , orbit
                      , linear
+                     , random
                      , gloss
   default-language:    Haskell2010