[ODE] objects in water

[Adam Moravanszky]

There is another interesting effect that we were seeing in a simulation 
recently: if you push a box down underwater all the way to the flat 
bottom of a pool, it will suddenly lose all buoyant force because there 
is no more liquid between it and the pool's floor.  In fact the liquid 
above will act to press it in place.  I don't know if this is 
experimentally repro-able in real life where it may be hard to get rid 
of *all* water below the box.

--Adam

Jon Watte wrote:

>>Here's a question: does penetration depth matter for buoyancy
>>calculations?  I'm guessing that buoyant objects deep underwater would
>>have more buoyant forces than objects close to the water's surface. 
>>Even so, it's probably not worth the effort to simulate this in most
>>real-time applications.
>>    
>>
>
>That's not true, except when you're partially intersecting the surface.
>
>When something is partially in water, and partially above it, it only 
>has as much floatation force as the part that's within the water. Once 
>the thing is fully submerged, it exerts the maximum floatation it can, 
>and pushing it further down won't exert more force (it's not a spring!)
>
>In fact, once you go further down, the object may start to compress 
>because of the high pressure, and thus its density goes up, and it gets 
>less buoyancy further down. Divers can feel this at 10 meters!
>
>Cheers,
>
>			/ h+
>
>
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