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Thread: Sandsphere, stick and roll on object

  1. #1

    Sandsphere, stick and roll on object

    Hola,

    I'm wondering, is it possible to make ClothFX objects stick to another object?
    I'm using the "stick" mode, but at no luck...

    Trying to get the spheres to roll around the object, but it only uses the default setting for some reason

    Sandstick testvideo


    Hope you can help,
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  2. #2
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    Could not see your whole screen, so I couldn't tell from the video, but it didn't look like the FX were calculated. Make sure you click calculate, or you will only get a rough approximation of the motion. Also, if doing a long calculation it is a good idea to save the motion once you get it right (file tab).
    Last edited by fgreen; 05-30-2007 at 01:17 PM.

  3. #3
    I'm not sure if I understand completely. You want to drop the spheres onto the 'sticky' collision object. Then they should roll down along the contours of the object, but they shouldn't fall off the object. Is that correct?

    Why do you use ClothFX? Is that because you think it will stick better, or do you want the spheres to act like cloth?

    Take a look at the movie I attached and see if this is more or less what you want.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  4. #4
    Yes, that's it.

    Thanks, very glad to see this works : )
    I'm no Dyn. person, but I had fidled a bit with ClothFX so it seemed right at the moment, I can't use particles combined with FXlinker though as it wouldn't look too good, cause I need the spheres to 'roll' around the object, but maybe I can use HardFX?
    (fgreen, thanks, nope though, i did calculate ; )

    Thanks for testing this, must be a setting somewhere.
    Now I'm gonna have some fun with testing some Sandman-like effects
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  5. #5
    Quote Originally Posted by erikals
    ... very glad to see this works...
    Well, there's good news and bad news...

    The good news seems to be that you're happy with the effect. It's not difficult to set up, but it does contain some manual repetitive work.

    The bad news: it's not HardFX, and the rolling motion isn't correct. I've been testing for hours and I don't think this can be done with HardFX.



    What I did:

    -- The spheres are FX-linked to a particle emitter. (As far as I could see, particles seem to be the only dynamic objects that work well in this case.)
    -- I baked the motion of the spheres. (Annoying: I added Motion Baker for the first sphere and then cloned it, but it only bakes the motion of the first sphere, so I had to add Motion baker to each sphere seperately.)
    -- I aligned the heading of the spheres to the path.
    -- I baked the motions again.
    -- For the rolling effect I used Dodgy's Wheel plugin (thanks Dodgy!). It adds rotation based on the length of the path, and it's easy to set up (but you have to add the plugin for each sphere seperately). There is a problem: because the spheres are aligned to the path, as they move down the object the rolling goes in the opposite direction. Maybe this can be done correctly with Relativity (Dr.Wheel / Dr.Cycler), but I don't know how...

    More good news: I'm not exactly an expert with dynamics and animation, so chances are that there are easier ways to set this up.

  6. #6
    Erikals, do the spheres have to roll down the object, or may they roll freely all over the surface (up/down/sideways)?

  7. #7
    Man, talk about helping out

    Quote Originally Posted by serge
    Erikals, do the spheres have to roll down the object, or may they roll freely all over the surface (up/down/sideways)?
    I don't think it is too important as I was thinking of using pathwind and other windtypes to control some of the motion.

    Doing things manually however is somewhat of a problem as the scene will end up using about 5000 spheres (or maybe more)
    heh : ) maybe I'm a bit stuck again.

    More good news: I'm not exactly an expert with dynamics and animation, so chances are that there are easier ways to set this up.
    me either so I guess we'll have to wait a bit, see what ideas comes around. ... I think I will post the example I showed as a bug though, as it should have worked. Either that, or making the "Stick" option unavailable for ClothFX somehow.

    Maybe there is another way...
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  8. #8
    Hm, my "edit" icon dissappeard,

    It seems "Stick" affects something after all, but till now I've gotten more of an "attract" effect instead of a "stick" effect.
    ..but wouldn't say it works.
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  9. #9
    Quote Originally Posted by erikals
    Man, talk about helping out
    Oh, don't give it a thought. It's a good opportunity for me to dive deeper into dynamics and animation.

    ...about 5000 spheres...
    Right... Well, HardFX isn't an option then. Too bad, cause I was on to something! I finally got it working with HardFX and correct rolling movement. Wasn't that difficult actually. Instead of a 'sticky' collision object I used a 'bouncy' object, and placed a gravity object in the centre. The spheres sticked perfectly on the surface, and with a small amount of "fix power" the spheres rolled correctly over the object. But 5000 HardFX spheres? Nah, I don't think so.

    I think your best bet is particles then. I don't know what you're up to exactly, but when you use 5000 or more spheres, is correct rolling movement still important? Check out the movie I attached. It's 2000 particles (hypervoxels) rolling over a 'sticky' collision object, a gravity object in the centre, and a rotation wind.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  10. #10
    It looks like maybe the best thing is a mix between hypervoxels and HardFX, I might know of a method, using metalink, that would reduce the calculationtime by quite a bit. I didn't quite get it though, by gravity object in the centre, do you mean a wind object in the midle of the object? I think I'm a bit off here But, in oter words, would it work e.g. on this object?
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  11. #11
    Hm, where is the edit button,.. gone again

    Here is what I got, hehe, not too close to sticking
    http://erikalstad.com/cgtemp/Sandarmroll.zip

    (included the files, for lw gurus to test)
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  12. #12
    Quote Originally Posted by erikals
    ... by gravity object in the centre, do you mean a wind object in the midle of the object?
    No, a gravity object (Items > Add > Dynamic Objects > Gravity).

    would it work e.g. on this object?
    That won't be easy since the object doesn't have an obvious centre. It might still be possible but very difficult. You'd have to place several Gravity-objects evenly thoughout the object. It will be quite a job to tweak all the settings (especially gravity and wind) to get it working right.


    Now, while checking your scene I had another idea. Check out the picture, and you might already see what I mean.

    Try the following (no need to change anything else in your scene):
    -- Open your object in modeler and delete the layer with the spheres.
    -- 'Smooth-scale' ("replicate") the object by 120 mm.
    -- Flip the polys (very important because of the collision).
    -- Set surface transparency to 100%.
    -- Save object under another name.
    -- Load this into your scene in Layout, and apply collisionFX for this object.
    -- Hit calculate.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	sandarm.jpg 
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  13. #13
    Quote Originally Posted by serge
    No, a gravity object (Items > Add > Dynamic Objects > Gravity).

    That won't be easy since the object doesn't have an obvious centre. It might still be possible but very difficult. You'd have to place several Gravity-objects evenly thoughout the object. It will be quite a job to tweak all the settings (especially gravity and wind) to get it working right.
    Ahh, never noticed that one. I think this might be something actually, I'll look a bit more into this method... it could be worth the effort.

    Quote Originally Posted by serge
    Now, while checking your scene I had another idea. Check out the picture, and you might already see what I mean.

    Try the following (no need to change anything else in your scene):
    -- Open your object in modeler and delete the layer with the spheres.
    -- 'Smooth-scale' ("replicate") the object by 120 mm.
    -- Flip the polys (very important because of the collision).
    -- Set surface transparency to 100%.
    -- Save object under another name.
    -- Load this into your scene in Layout, and apply collisionFX for this object.
    -- Hit calculate.
    Hehe Already tried that one, it sort of works, but not quite, the spheres spin in a weired way.

    Thanks again
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