Actual gravity

app.rb

@@ -3,7 +3,7 @@ require "gosu"
 load "physobj.rb"
 
 class Window < Gosu::Window
-	attr_accessor :caption, :physobjs, :planets
+	attr_accessor :freeze, :caption, :physobjs, :planets
 	attr_reader :width, :height
 
 	def initialize(title, width, height, physobjs = [], planets = [])
@@ -13,24 +13,48 @@ class Window < Gosu::Window
 
 		@physobjs = physobjs
 		@planets = planets
+
+		@font = Gosu::Font.new(self, Gosu::default_font_name, 12)
+		@font2 = Gosu::Font.new(self, Gosu::default_font_name, 32)
+		@freeze = false
 	end
 
-	def update
-		@physobjs.each do |obj| 
-			obj.physics 
+	def button_up(id)
+		super id
+
+		if( id == Gosu::KbEscape ) then
+			@freeze = !@freeze
 		end
+	end
 
-		@planets.each do |planet|
-			planet.orbit(@physobjs)
+	def update
+		if( !@freeze ) then
+			@physobjs.each do |obj| 
+				obj.physics 
+			end
+
+			@planets.each do |planet|
+				planet.orbit(@physobjs)
+			end
 		end
 	end
 
+	private def generate_debug_string(obj)
+		return "\n#{obj.name}\nVel:    #{obj.vel.round(4)} (#{obj.vel.magnitude.round(1)})\nAccel:    #{obj.accel.round(4)} (#{obj.accel.magnitude.round(4)})\nPos:    #{obj.pos.round(4)}\n"
+	end
+
 	def draw
+		if( @freeze ) then
+			@font2.draw("FROZEN", 0, 0, 1, 1.0, 1.0, Gosu::Color::WHITE)
+		end
+
 		@physobjs.each do |obj| 
 			obj.render
 			obj.draw_vector(obj.vel, 10)
 			obj.draw_vector(obj.accel, 500, 0xff_aaffaa)
 			obj.render_path
+
+			@font.draw(self.generate_debug_string(obj), obj.pos[0], obj.pos[1], 1, 1.0, 1.0, Gosu::Color.argb(0xee_aaaaff))
 		end
 
 		@planets.each do |planet|
@@ -42,16 +66,16 @@ end
 
 window = Window.new("Physics!", 1600, 900)
 
-planet = Planet.new("Earth", window, 0xff_aaffaa, 0.0001)
+planet = Planet.new("Earth", window, 0xff_aaffaa)
 planet.pos = Vector[800, 450]
 
 cube = PhysCube.new("Cube", window, 8, 8)
-cube.pos = Vector[800, 450 + 100]
-cube.vel = Vector[4, 0]
+cube.pos = Vector[800, 450 + 200]
+cube.vel = Vector[2.5, 0]
 
 cube2 = PhysCube.new("Cube2", window, 8, 8)
-cube2.pos = Vector[800, 450 + 500]
-cube2.vel = Vector[5, 0]
+cube2.pos = Vector[800, 450 + 400]
+cube2.vel = Vector[1.25, 0]
 planet.orbit([cube, cube2])
 
 window.planets << planet

gosu_plugin.rb

@@ -0,0 +1,43 @@
+require "gosu"
+
+module Gosu
+
+	def self.draw_circle(x, y, r, c, z = 0, thickness = 1, sides = nil, mode = :default)
+
+		# Unless specified, calculate a nice-looking "minimum" number of sides
+		# sides = (r + Math::sqrt(r * 0.1) * 4).floor if sides.nil?
+		sides = (2.0 * r * Math::PI).floor if sides.nil?
+
+		# Calculate the inner and outer offsets from the "true" circle
+		offs = thickness * 0.5
+		r_in = r - offs
+		r_out = r + offs
+
+		# Calculate the angular increment
+		ai = 360.0 / sides.to_f
+
+		translate(x, y) {
+			ang = 0
+			while ang <= 359.9 do
+				draw_quad(
+					Gosu.offset_x(ang, r_in), Gosu.offset_y(ang, r_in), c,
+					Gosu.offset_x(ang, r_out), Gosu.offset_y(ang, r_out), c,
+					Gosu.offset_x(ang + ai, r_in), Gosu.offset_y(ang + ai, r_in), c,
+					Gosu.offset_x(ang + ai, r_out), Gosu.offset_y(ang + ai, r_out), c,
+					z, mode
+				)
+				ang += ai
+			end
+		}
+
+	end
+
+	class Window
+
+		def draw_circle(x, y, r, c, z = 0, thickness = 1, sides = nil, mode = :default)
+			Gosu::draw_circle(x, y, r, c, z, thickness, sides, mode)
+		end
+
+	end # Window class
+
+end # Gosu module

physobj.rb

@@ -1,6 +1,7 @@
 require "matrix"
+load "gosu_plugin.rb"
 
-GRAV_CONSTANT = 1e+2
+GRAV_CONSTANT = 1e+1
 
 class PhysObj
 	attr_accessor :world, :saved_pos, :pos, :vel, :accel, :x, :y
@@ -29,7 +30,7 @@ class PhysObj
 
 	def render_path
 		@saved_pos.each do |pos|
-			Gosu.draw_rect(pos[0], pos[1], 2, 2, Gosu::Color.argb(0xaa_ccccff))
+			Gosu.draw_rect(pos[0], pos[1], 2, 2, Gosu::Color.argb(0x44_ccccff))
 		end
 	end
 
@@ -78,17 +79,20 @@ end
 
 
 class Planet < PhysCube
-	attr_reader :gravity
-	def initialize(name, world, color, gravity=0.05)
-		super name, world, 10, 10, color
+	attr_reader :mass
+	def initialize(name, world, color, mass=1e+2)
+		super name, world, 40, 40, color
+		@mass = mass
+	end
 
-		@gravity = gravity
+	private def calculate_gravity_scalar(obj, dir_vec)
+		grav = GRAV_CONSTANT * (self.mass/(dir_vec.magnitude**2))
+		return grav
 	end
 
 	private def calculate_gravity_vector(obj)
 		dir_vec = self.pos - obj.pos + Vector[self.width/2, self.height/2]
-		return dir_vec * self.gravity
-		# return (self.gravity * dir_vec)/(dir_vec.magnitude)
+		return (dir_vec/dir_vec.magnitude) * calculate_gravity_scalar(obj, dir_vec)  
 	end
 
 	def orbit(physobjs)
@@ -97,4 +101,8 @@ class Planet < PhysCube
 			obj.accel = grav_vec
 		end
 	end
+
+	def render
+		Gosu.draw_circle(self.pos[0], self.pos[1], 20, @color)
+	end
 end