[Imstk-developers] Rendering interpolation/extrapolation

[Sreekanth Arikatla]

Hi Nick,
            Great article. good to know that Hermite can eliminate some
artifacts of linear interpolation. This could definitely be considered for
iMSTK. Thanks.

On Thu, Dec 1, 2016 at 8:01 PM, Milef, Nicholas Boris <milefn at rpi.edu>
wrote:

> Ok, so I did some more digging around, and I found this article with some
> useful animations:
> http://gafferongames.com/networked-physics/snapshots-and-interpolation/
>
> If you look at the last animation, it shows what happens when you use
> extrapolation vs. interpolation (for networking, but it's the same idea). I
> think interpolation makes sense for our application based on these results.
> I think that extrapolation is mainly used for animation and character
> movement in games.
> ------------------------------
> *From:* Sreekanth Arikatla [sreekanth.arikatla at kitware.com]
> *Sent:* Tuesday, November 29, 2016 12:38 PM
> *To:* Alexis Girault
> *Cc:* Milef, Nicholas Boris; imstk-developers at imstk.org
> *Subject:* Re: [Imstk-developers] Rendering interpolation/extrapolation
>
> Hi Alexis, Nick,
>                  In our case i think the first thing we should do, which
> is easy, is to make the time step dT used by the physics module adaptive.
> It should be the set to the delta T that is measured in terms of the wall
> clock time between two successive physics solves. Once this is done we
> encounter the problem that Nick had mentioned.
>
> In that case:
>
>    1. If the lowest frame rate amongst all of physics objects is more
>    than 30 Hz then we shouldn't observe much of a difference (unless we are
>    dealing with haptics).
>    2. If the lowest frame rate amongst all of physics objects is less
>    than 30 Hz then we will observe something like stop motion animation. In
>    that case we need to probably use one of the options suggested from the
>    link: extrapolation or interpolation. Extrapolation might work if there is
>    no sudden and drastic change in direction of motion of parts of the scene
>    else you will see artifacts. If we choose interpolation, then i think we
>    are forced to lag by one time step and also choose the linear interpolation
>    constant (slope) adaptively. This could work but I myself have never tried
>    this. One problem I see is that if the frame rates are really low like 4fps
>    then if the user tries to interact with the objects, they will observe the
>    lag of one time step enforced by the method. If it is not interactive it
>    should be fine I guess.
>
> Implementation wise adaptive time step and interpolation/extrapolation
> should not be very difficult. Its a good discussion to have. Let me know
> what you guys think.
>
> Thanks.
>
>
>
> On Tue, Nov 29, 2016 at 11:39 AM, Alexis Girault <
> alexis.girault at kitware.com> wrote:
>
>> Sreekanth, what's your take on our possible update rate for the physics
>> modules?
>>
>> Alexis Girault
>> R&D Engineer in Medical Computing
>> Kitware, Inc.
>>
>> http://www.kitware.com
>> (919) 969-6990 x325
>>
>> On Tue, Nov 29, 2016 at 11:02 AM, Milef, Nicholas Boris <milefn at rpi.edu>
>> wrote:
>>
>>> How are we handling different update rates from the physics modules in
>>> the rendering? I imagine this will be a pretty severe problem for physics
>>> modules with low update rates.
>>>
>>> http://gamedev.stackexchange.com/questions/12754/how-to-inte
>>> rpolate-between-two-game-states
>>>
>>> _______________________________________________
>>> Imstk-developers mailing list
>>> Imstk-developers at imstk.org
>>> http://public.kitware.com/mailman/listinfo/imstk-developers
>>>
>>>
>>
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>>
>>
>
>
> --
> Sreekanth Arikatla, Ph.D,
> Senior R&D Engineer,
> Kitware, Inc. <http://www.kitware.com>, Carrboro, NC.
>
>


-- 
Sreekanth Arikatla, Ph.D,
Senior R&D Engineer,
Kitware, Inc. <http://www.kitware.com>, Carrboro, NC.
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