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AppGameKit Classic Chat / Question about orbiting planets

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haliop_New

User Banned

Posted: 31st Dec 2016 13:29 Edited at: 31st Dec 2016 13:35

so i have an Earth planet and the Moon planet in my game
i can orbit them using Sin and Cos
but one thing is unclear to me
how can i add the x y z positions of the planet Earth if its not on 0,0
cause i play with it a bit

how can i use Sin and Cos in a way that it will orbit at a new given location rather then just 0,0,0
please help

pseudo code will be very helpful
thank you for your time.
haliop.

edit:
for the example
lets say
planet earth is at 150000000,0,150000000
and the moon is at 150000000-346000,0,150000000

how do i add the current x and current z to the sin/cos algo ?

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CumQuaT

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Joined: 28th Apr 2010

Location: Tasmania, Australia

Posted: 31st Dec 2016 14:11

I did a sort of similar thing in my game, as everything rotates around a 3D tower. What I did, between syncs, was to position everything at the center of its "orbit", rotate it accordingly to it's rotation around the tower, then did a local translation so that the object moved out from the central pivot of its orbit and ended up in the correct position before the next sync.

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Ortu

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Joined: 21st Nov 2007

Location: Austin, TX

Posted: 31st Dec 2016 17:17 Edited at: 31st Dec 2016 17:35

earthx = anchorpointx + sin (orbitangle) * orbitdistance 
earthz = anchorpointz + cos (orbitangle) * orbitdistance 

moonx = earthx + sin (moonangle) * moondistance
moonz = earthz + cos (moonangle) * moondistance

http://games.joshkirklin.com/sulium

A single player RPG featuring a branching, player driven storyline of meaningful choices and multiple endings alongside challenging active combat and intelligent AI.

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haliop_New

User Banned

Posted: 1st Jan 2017 08:37

Ortu you are the best !
i thought it would look something similar
now im wondering if i should stop assuming i know stuff just do them see what happens

this is awesome thank you man. really appreciate it.

CumQuat i didnt really understand what your'e saying

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CumQuaT

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Location: Tasmania, Australia

Posted: 1st Jan 2017 13:33

I must have misunderstood the question :\

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Ched80

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Joined: 18th Sep 2010

Location: Peterborough, UK

Posted: 1st Jan 2017 14:27

Be careful with the values you are using, AppGameKit tier 1 only holds 7dp. This can affect how smooth your orbits are in game.

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haliop_New

User Banned

Posted: 1st Jan 2017 16:41

Ched its just for scenery
but can you explain a bit more ?
what should i look at ? or be warned about ?
a bit of explanation will be awesome.
thank you.

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Ortu

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Location: Austin, TX

Posted: 1st Jan 2017 16:53

Using numbers larger than 7 digits (I think are truncated) values may not behave as you expect

http://games.joshkirklin.com/sulium

A single player RPG featuring a branching, player driven storyline of meaningful choices and multiple endings alongside challenging active combat and intelligent AI.

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haliop_New

User Banned

Posted: 17th Jan 2017 11:13

Ortu , This dosent work well
the moon collides with Earth...

can someone help ?
I don't know how to get SIn and Cos to work from a starting location which is far from the object its orbating and keeping the same distance

what Ortu suggests just puts the moon at a location which is yes far enough from earth using the distance I entered but it dosent orbit earth very well...

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Markus

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20

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Joined: 10th Apr 2004

Location: Germany

Posted: 17th Jan 2017 12:07

sin / cos give you a value between -1 and 1 , so its left/right up/down if you useing it for x and y axis, the angle parameter from 0-360° (in circle) just belongs the output from -1 to 1
it is not necessary to use sinus and cosinus but it is still frequently used.
if you multiply a length with this -1 until 1 for one axis it is more left or right but if you multiply for x and y axis you go along this direction, so this result describes a position at x,y axis.
this sin/cos thing always rotate around x=0,y=0
if you will rotate the moon around the earth but earth have a position 20,10 you must subtract is first, get new values from sin * distance & cos * distance and add this 20,10 again.

AGK (Steam) V2017.01.09 : Windows 10 Pro 64 Bit : AMD (16.12.1) Radeon R7 265 : Mac mini OS Sierra (10.12.2)

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haliop_New

User Banned

Posted: 17th Jan 2017 12:15

this is what I currently use but its not good

moonx = earthx + sin (moonangle) * moondistance
moonz = earthz + cos (moonangle) * moondistance

you said you need to add the values of earth positions but that's not good....
how would you fixed it ?

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PSY

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Joined: 3rd Jul 2016

Location: Laniakea Supercluster

Posted: 17th Jan 2017 15:07 Edited at: 17th Jan 2017 16:36

Could be a rounding error caused by a wrong variable type, or incorrect angle calculation.

I set up a demo code which orbits earth around the sun and the moon around earth, using simple sin/cos calculations. Maybe you can locate your bug by having a look at it

#option_explicit

SetWindowTitle( "Orbits" )
SetVirtualResolution ( 1024, 768 )
SetSyncRate ( 60, 1 )

#constant EARTHDISTANCE = 300
#constant MOONDISTANCE = 70

global sunx as float = 512.0
global sunz as float = 384.0
global earthx as float
global earthz as float
global moonx as float
global moonz as float
global earthangle as float 
global moonangle as float

repeat
	earthangle	= fmod ( earthangle + 0.5, 360.0 )
	moonangle	= fmod ( moonangle + 1.5, 360.0 )
	
	earthx	= sunx + cos ( earthangle ) * EARTHDISTANCE
	earthz 	= sunz + sin ( earthangle ) * EARTHDISTANCE
	moonx 	= earthx + cos ( moonangle ) * MOONDISTANCE
	moonz 	= earthz + sin ( moonangle ) * MOONDISTANCE
	
    DrawEllipse ( sunx, sunz, 45, 45, MakeColor ( 255, 0, 0 ), MakeColor ( 255, 255, 0 ), 1 )
    DrawEllipse ( earthx, earthz, 20, 20, MakeColor ( 0, 0, 255 ), MakeColor ( 0, 255, 255 ), 1 )
    DrawEllipse ( moonx, moonz, 8, 8, MakeColor ( 255, 255, 255 ), MakeColor ( 100, 100, 100 ), 1 )
    
    Sync()
until GetRawKeyPressed ( 57 ) or getrawkeypressed ( 27 )
end

#option_explicit

SetWindowTitle( "Orbits" )
SetVirtualResolution ( 1024, 768 )
SetSyncRate ( 60, 1 )

#constant EARTHDISTANCE = 300
#constant MOONDISTANCE = 70

global sunx as float = 512.0
global sunz as float = 384.0
global earthx as float
global earthz as float
global moonx as float
global moonz as float
global earthangle as float 
global moonangle as float

repeat
	earthangle	= fmod ( earthangle + 0.5, 360.0 )
	moonangle	= fmod ( moonangle + 1.5, 360.0 )
	
	earthx	= sunx + cos ( earthangle ) * EARTHDISTANCE
	earthz 	= sunz + sin ( earthangle ) * EARTHDISTANCE
	moonx 	= earthx + cos ( moonangle ) * MOONDISTANCE
	moonz 	= earthz + sin ( moonangle ) * MOONDISTANCE
	
    DrawEllipse ( sunx, sunz, 45, 45, MakeColor ( 255, 0, 0 ), MakeColor ( 255, 255, 0 ), 1 )
    DrawEllipse ( earthx, earthz, 20, 20, MakeColor ( 0, 0, 255 ), MakeColor ( 0, 255, 255 ), 1 )
    DrawEllipse ( moonx, moonz, 8, 8, MakeColor ( 255, 255, 255 ), MakeColor ( 100, 100, 100 ), 1 )
    
    Sync()
until GetRawKeyPressed ( 57 ) or getrawkeypressed ( 27 )
end

Cheers,
PSY

PSY LABS Games
Coders don't die, they just gosub without return

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Markus

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Joined: 10th Apr 2004

Location: Germany

Posted: 17th Jan 2017 15:30

Quote: " but its not good "

the values you will see if you set a break point and start in debugmode and add this variables in the watch list.

AGK (Steam) V2017.01.09 : Windows 10 Pro 64 Bit : AMD (16.12.1) Radeon R7 265 : Mac mini OS Sierra (10.12.2)

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Phaelax

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Joined: 16th Apr 2003

Location: Metropia

Posted: 18th Jan 2017 12:37

Browse through the AppGameKit Challenge thread, not long ago we made solar system simulations. If you want accurate planet orbits the data is all there.

"I like offending people, because I think people who get offended should be offended." - Linus Torvalds

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haliop_New

User Banned

Posted: 19th Jan 2017 13:30

still not working well...
I think its because I use the 3d world in millions of units maybe AppGameKit cant handle 10000000 and such numbers...
i'll try to create a simple app to check it but currently its not working the moon and earth still collides....

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haliop_New

User Banned

Posted: 19th Jan 2017 13:31

OOPS MY BAD

it does work I used GetObjectY for the Z value that is why they collided.

thanks everyone for the help , really appreciate it .

haliop.

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