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Question Help with orbital math/physics

Discussion in 'Physics' started by mistercow3417, May 12, 2020.

  1. mistercow3417

    mistercow3417

    Joined:
    May 12, 2020
    Posts:
    3
    So I have a scene with a Star and planet it it. I used this equation to calculate force between bodies: F = G * ((M1 * M2) / distance^2). I set G (gravitational constant0 to 0.647f, a bigger number than in rl to test this. It worked fine. When I set G to the real world value of 0.0000000000647f, the planet (lower mass and size than star) would not move but the star would be dragged towards the planet.
    Help?
    Thanks. :)
     
    mistercow3417, May 12, 2020
    #1

  2. Edy

    Edy

    Joined:
    Jun 3, 2010
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    2,440
    Most probably you're using floats beyond their capacity. Floats can store up to 7 significant digits. This means that 0.0000000000647f cannot be stored in a float, and it's effectively zero. The smallest number a float can store is about 0.0000001f.

    You should use doubles for your calculations everywhere, including the positions of your bodies. Only convert the resulting positions to floats for actually positioning the objects in the scene.
     
    Edy, May 12, 2020
    #2
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  3. mistercow3417

    mistercow3417

    Joined:
    May 12, 2020
    Posts:
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    Thanks
     
    mistercow3417, May 13, 2020
    #3

  4. koirat

    koirat

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    Jul 7, 2012
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    2,031
    You got bug somewhere.
    Whatever the result of F is, the lighter body should accelerate faster than heavier body.
     
    koirat, May 13, 2020
    #4
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  5. mistercow3417

    mistercow3417

    Joined:
    May 12, 2020
    Posts:
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    Yeah that is what happens when G is a lower number
     
    mistercow3417, May 14, 2020
    #5