Orbit stuff

[Garmelon]

This is a small project I made for a presentation about orbital mechanics a while ago (I used a modified version of this though).
Don't expect this to be polished or working in any way - some of the comments in the code are in German.

[Nixola]

Could I please ask you to lower your requirements a bit? I highly doubt that you actually need 16x MSAA or the biggest canvas possible in this thing, and the performance loss (as well as the hassle for some people to go and edit your code to actually run this) isn't exactly negligible.

[qubodup]

I like to use this for paining

http://youtu.be/AefcH3ilnaE

Strange, I thought there was something similar released on the love2d forums recently but I can't find it again.

[Garmelon]

Yep, I have seen that one too

[Muzz]

I have some actual orbital physics stuff written in Lua that you could use? I made it for moai but it would be really easy for you to port to LOVE2d, as all it does is take is two box2d bodies and their properties and outputs a table with a bunch of xy coordinates that you can plug into a line drawer.

Constant should be the universal gravitational constant.

The orbital physics are all from here which you may need to read to understand what is going on. http://www.braeunig.us/space/orbmech.htm

Code: Select all

function PhysActor:CalculateOrbit()
--This function derives everything you need to know about a single orbiting body. 

			local bodyPos = Vector.new(self.body:getPosition())
			local bodyVel = Vector.new(self.body:getLinearVelocity())		

			local celPos = Vector.new(self.currentCelestialB.body:getPosition())		

			--get the velocity of the body
			local V = bodyVel:length()		

			--get the distance from the foci
			local R = bodyPos:distanceTo(celPos)		

			--Get the Zenith Angle
			local Anglefrombody  =  bodyPos:angleTo(celPos)
			local bodyFromAngle  =  celPos:angleTo(bodyPos)
			local Angle = math.deg( math.atan2(bodyVel.y,bodyVel.x))
			local Zenith =  Angle - Anglefrombody 
			local GM = (constant * self.currentCelestialB.body.fakeMass)
	

			-- tan V  = (r1 × v12 / GM) × sin  × cos  / [(r1 × v12 / GM) × sin2  - 1
			--tanV = (6628140*math.pow(7900,2)/3.986005e14) * math.sin(math.rad(89)) * math.cos(math.rad(89)) / ((6628140*math.pow(7900,2)/3.986005e14) * math.pow(math.sin(math.rad(89)),2) - 1)
			-- this formula is to locate where the body is from the perrigee
			local tanVx = (R*math.pow(V,2)/GM) * math.sin(math.rad(Zenith)) * math.cos(math.rad(Zenith)) 
			local tanVy =  ((R*math.pow(V,2)/GM) * math.pow(math.sin(math.rad(Zenith)),2) - 1)
			local tanV = math.atan2(tanVx,tanVy)

			local tanVDeg = math.deg(tanV)
			local PerigeeFromZeroAngle =  bodyFromAngle - ( tanVDeg - 180) --WOOO!
			local PerigeeFromZeroAngle =  bodyFromAngle -  tanVDeg  --WOOO

			local C = (2 * GM) / (R* math.pow(V,2))

			local Rh = (-C + math.sqrt( math.pow(C,2) - 4 * (1-C) * -math.pow(math.sin(math.rad(Zenith)),2) )) / (2*(1-C))
			local Rl = (-C - math.sqrt( math.pow(C,2) - 4 * (1-C) * -math.pow(math.sin(math.rad(Zenith)),2) )) / (2*(1-C))		
		
			local Rlower = math.min(Rh,Rl)
			local Rhigher = math.max(Rh,Rl)		

			local PerigeeRadius = R * Rlower 
			local ApogeeRadius = R * Rhigher		

			--Eccentricity
			--e = SQRT[ (r1 × v12 / GM - 1)2 × sin2  + cos2  ]
			local E = math.sqrt( math.pow((R * math.pow(V,2)/ GM -1),2) * math.pow(math.sin(math.rad(Zenith)),2) + math.pow(math.cos(math.rad(Zenith)),2))		


			--SEMI MAJOR AXIS
			--a = 1 / ( 2 / r1 - v12 / GM )		

			local SemiMajorAxis = 1/(2 / R - math.pow(V,2) / GM)

			--theta = E * math.sin(math.rad(225)) /  (1 + E * math.cos(math.rad(225)))
			--theta = 0.1 * math.sin(math.rad(225)) /  (1 + 0.1 * math.cos(math.rad(225)))
			--theta = math.atan(theta)		

  
			 self.predictedPoints = {}
			 self.predictedPoints2 = {}		
			 self.perigee = {}
			 self.currentAng = {}

			-- print("Vel:"..V)
			-- print("initDist"..R)
			--print("perigeeFromZero:"..PerigeeFromZeroAngle,tanVDeg)
			-- print("eccentricity:"..E)
			-- print("PerigeeRadius:"..PerigeeRadius)
			-- print("ApogeeRadius:"..ApogeeRadius)
			-- print("SemiMajorAxis:"..SemiMajorAxis)
			-- print("C:"..C)
			-- print("Zenith:"..Zenith)
			-- print("Velocity:"..V)

			self.perigee[1] = 0
			self.perigee[2] = 0	
			self.perigee[3] = math.cos(math.rad(PerigeeFromZeroAngle))*(PerigeeRadius)
			self.perigee[4] = math.sin(math.rad(PerigeeFromZeroAngle))*(PerigeeRadius)

			self.currentAng[1] = 0
			self.currentAng[2] = 0	
			self.currentAng[3] = math.cos(math.rad(PerigeeFromZeroAngle+tanVDeg))*(PerigeeRadius)
			self.currentAng[4] = math.sin(math.rad(PerigeeFromZeroAngle+tanVDeg))*(PerigeeRadius)


			for i=1,361 do
				Vang = i 

				--V is angle from perrigee		

				PointDist = SemiMajorAxis * (1- math.pow(E,2)) / (1+ E * math.cos(math.rad(Vang)))		
		
				PointAngle =   Vang +  PerigeeFromZeroAngle
				--PointAngle =   Vang

				Point = Vector.new(PointDist*math.cos(math.rad(PointAngle)),PointDist*math.sin(math.rad(PointAngle)))		

				table.insert(self.predictedPoints,Vang+800)
				table.insert(self.predictedPoints,PointDist/10)
				table.insert(self.predictedPoints2,Point.x)
				table.insert(self.predictedPoints2,Point.y)	

			end		
		
end

[Ranguna259]

This looks like this.

[kikito]

Could I please ask you to lower your requirements a bit? I highly doubt that you actually need 16x MSAA or the biggest canvas possible in this thing, and the performance loss (as well as the hassle for some people to go and edit your code to actually run this) isn't exactly negligible.

My computer (Mac Book Air) can't create the canvas your game requests.

[Garmelon]

This looks like this.

I used the canvas initialisation part of that thing...

[raingloom]

Same problem on latest XUbuntu with MSI GTX 650.