TopCat3005

Q: Orbit around with high strength leads to orbit increasing...

I'm trying to model a solar system, with accurate orbit times for the planets. I need to set the speed (strength) really high (490) on one of the planets, but this leads to it losing a stable orbit. Can anyone help?

 

Steve

Posted on Jan 18, 2016 3:26 AM

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Q: Orbit around with high strength leads to orbit increasing...

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  • by Karsten Schlüter,

    Karsten Schlüter Karsten Schlüter Jan 18, 2016 9:18 AM in response to TopCat3005
    Level 7 (32,703 points)
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    Jan 18, 2016 9:18 AM in response to TopCat3005

    TopCat3005 wrote:

    ...  but this leads to it losing a stable orbit. Can anyone help?

    only one man can help …

    "Scotty! More energy!!" ...

    scnr

     

     

    hmmm, I don't quiet understand what  exactly do you mean by 'losing orbit'?

    Bildschirmfoto 2016-01-18 um 18.05.59.jpg

    both methods, Orbit around (for a simple circle), or Motion Path (for a correct ellipsis) deliver a stable orbit ...

    see, my speed is 500 ....

     

    sure, when you crank up speed too much, you should consider applying motion blur ... otherwise, the planet just 'hops' arround ...

    Bildschirmfoto 2016-01-18 um 18.16.58.jpg

  • by TopCat3005,

    TopCat3005 TopCat3005 Jan 19, 2016 5:17 AM in response to Karsten Schlüter
    Level 1 (0 points)
    Jan 19, 2016 5:17 AM in response to Karsten Schlüter

    StarTrekXII-MrScott.jpg

     

    But seriously... here's a screen grab of my problem...

     

    screen shot.png

  • by GFXZen,

    GFXZen GFXZen Jan 19, 2016 12:52 PM in response to TopCat3005
    Level 4 (1,647 points)
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    Jan 19, 2016 12:52 PM in response to TopCat3005

    First, try using the Exponential falloff option.


    The behavior your seeing looks like this is related to the length of your project (+12,000 frames) and the speed setting.  BTW, I don't know what your delivery requirements are, but does this really need to be that long?

     

    Additionally there are always other ways to approach things like this.  Another option is to offset the shape using the anchor or a parent group that you animate and then use a behavior like rate on each planet/parent group to set the speed of rotation. Mathematically this might be easier to get accuracy as you can set the earth to have 1 rotation/time period and then adjust other planets using something like the orbital values here: http://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_ratio.html

  • by fox_m,

    fox_m fox_m Jan 19, 2016 5:45 PM in response to TopCat3005
    Level 5 (5,517 points)
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    Jan 19, 2016 5:45 PM in response to TopCat3005

    It looks like you're using the Group "Sun" to orbit around... What else is in that group besides the Circle shape?

     

    That asked, I agree with Karsten, using Motion Paths makes much more sense. For one, you can actually show the orbital paths.

     

    If you're having a lot of trouble with the Orbit Around simulation, there are easier options to deal with. One of the things I notices with Orbit Around is the more you "push" the Strength, the more the path flattens in segments around the orbit — eventually, the orbit is no longer circular (or logarithmic if you increase the Drag) but more and more polygonal. I wasn't able to replicate the problem you illustrated and I pushed the Strength into the thousands.

     

    Other methods:

    Using Motion Paths is not without problems... For one, Motion keeps resetting the Custom Speed parameter to auto-animate, so every time you add or change some setting, you have to reset the parameter to clear the auto-keyframes on Custom Speed.

     

    planetaryOrbitsGIF.gif

    [disclaimer: no attempt was made at accuracy here. The sun is way too small and the planets are only relatively sized smaller than, larger than... etc. Saturn and Jupiter are groups; both have two circles in the group and the group is animated, not the circles.]

     

    Setting the timing for each Motion Path can be accomplished with an Oscillate behavior linked to the Custom Speed Set to a Sawtooth pattern. The problem you get stuck with is the fact that Oscillate produces values that go from -Amplitude to +Amplitude, so a method needs to be devised to offset the amplitude values +50% and set the Amplitude to 50% so that the values generated will go from 0 - 100%. I handle that by adding a Numbers generator to the project and turn off Animate and set the Value to 50. I use a Link Behavior with the Apply Mode set to Add to Source. Then on top of that (behavior "order" is important in the instance) I add the Oscillate (sawtooth, 50% amplitude) and set the Speed I want the object to move over the Motion Path. If you're going to rotate the view of the orbits (as I have done in the gif above) you'll want to add a Basic Motion > Point At behavior and drop the Camera (add one if you haven't already) into the Object well (set the Transition to 0% - leave the rest of the defaults). When you're done adding behaviors, go back to the Motion Path and Reset Parameter on the Custom Speed (it should behave as expected at that point.) [This method was used for the animation above.]

     

    Another way to orbit an object around a point is to use the Basic Motion > Spin Behavior.  To adjust the object so it orbits around a point, Adjust the X (or Y) Anchor Point to create the radius.  The X & Y position parameters will adjust the center of orbit. You can set a small scale oscillator (carefully timed!) on the anchor point to create elliptical orbits (add the Spin after the Oscillator).

     

    [This is probably the most absurd way... but it works and it illustrates a slightly different method to apply a Numbers value.]

    Another way to go is to draw your orbit with a Circle (ellipse) and turn off the Fill. Set the Width to the size of your planet. To the First Point Offset, add a Link behavior and use the same Circle as the Source object and the Last Point Offset as the Source Parameter. At the bottom, set the Last Point Offset offset to -0.1 (you should get a simple circle shape.) Add a Numbers generator (you can turn off its visibility) and turn off Animate. Add an Oscillate behavior to the Value parameter, and in the Oscillate behavior controls, set the Amplitude to 50. You will use the Speed in this behavior to control the orbital motion. Back in the Circle object, add a Link behavior to the Last Point Offset and drop the Numbers generator in the Source Object well. Click the Compatible Parameters button and set the Source Parameter to Object > Numbers > Value. At the bottom of the Link behavior, set the Value offset to 50.  You can make a duplicate of the circle shape and set the outline to a width of 1point and with normal First and Last Point offsets, you will have the orbit path that can be shown. [Use of the Numbers generator in this manner can be applied to the first method above as well... the benefit with this method is that you don't have to deal with the Motion Path Custom Speed "problem" (if you ask Apple, it's probably a "feature"...LOL).]

     

    ... and the vote for Easiest Method goes to ...

    Another way is to Replicate your circles. Set the Shape to Circle and Arrangement to Outline. Set Points to 1. Design your Radius.  To the Offset parameter, add a Rate parameter behavior. Set your speed. Offset will go to infinity, so you don't have to deal oscillating between a min and max value. Check 3D, and if you tilt the orbit, you can check the Face Camera parameter to keep the circle parallel to the canvas. [As an alternative, draw an ellipse for the orbit, set the Shape parameter in the Replicator to Geometry and add the ellipse to the source well. To show the elliptical orbit with the replicator animation, add both into a group and rotate the group -- the Face Camera parameter will keep the "planet" upright.]

     

    ...and then there's the stuff you can do with 3D: (uses spin/anchor pt method - "textures" done with Clouds generators)

    2planets3D.gif

  • by Karsten Schlüter,

    Karsten Schlüter Karsten Schlüter Jan 19, 2016 11:26 PM in response to TopCat3005
    Level 7 (32,703 points)
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    Jan 19, 2016 11:26 PM in response to TopCat3005

    TopCat3005 wrote:

    …But seriously... here's a screen grab of my problem...

     

    That looks … not good.

    Looks for me like some technical failure…

    But I'm no engineer - could be complexitity/sheer size of your project 'overwhelms' Motion, and/or your graphic card, and/or a Ram issue, and/or what ever.

     

    Have you tried in a reduced, quick'n dirty 'test'-project, sun+planets just circles/'dots', what's happening? varying length of project (6 min is indeed long …), varying numbers of planets (don't tell Neil deGrasse!!), ...?

     

    And try to follow our experts suggestions, .... I dare to say, you made it a bit more complicated than needed (but simplified by using circle orbits…); e.g. I don't like to 'paint' in M5, prefer to create elements in some paint.app as Pixelmator, in final size, saved as png, and use Motion to <punpahh> motion things ...

     

    Or that Snap Alignment behavior could probably be replaced by a simple 'face to camera', even when you use only two dimensions in a 3D project ....

     

     

    my sun looks a lil' … childish compared to others ...


    linus.jpg  hmm, I am that foolish ... LOL!

  • by TopCat3005,

    TopCat3005 TopCat3005 Feb 7, 2016 2:11 PM in response to Karsten Schlüter
    Level 1 (0 points)
    Feb 7, 2016 2:11 PM in response to Karsten Schlüter

    It's getting there guys - motion paths rather than orbits has done the trick