[Sidefx-houdini-list] CHOP invalid source

François Duchesneau houdini at trinix.ca
Wed Nov 22 09:20:49 EST 2017


If you want to do an animation smooth in vex you'll have to query a 
certain amount of previous and future frames. Chop does exactly that 
with a lot of control and you get an instant visual representation of 
the smoothed curve. Doing all that in vex would be much more complicated 
and unintuitive. If you're only concerned about chop performances, you 
can always split the operation in 10 different sets of points and 
distribute that on a farm for example.

Francois

On 11/22/2017 08:45 AM, Jerome Pastorello wrote:
> Thanx a lot guys,
>
> Indeed it works fine with a brand new scene without any traces of (Carbon) simulation.
>
> Anyone knows a ressource where I could learn how to implement a vex smoothing algorythm ?
>
> Many thanx anyway, not enough sleep prevent you from thinking the right way.
>
> Jérôme
>
>
>
>
>> Le 22 nov. 2017 à 14:16, Sean Lewkiw <slewkiw at cinesite.com> a écrit :
>>
>> I have had a lot of trouble in the past with CHOPs force-cooking OPs that were not required.  Could it be possible that CHOPs is re-cooking your entire cloth sim?  I'd make sure that this sim is completely gone from the scene.
>>
>> If all you need to do is smooth the jitter of a single point, object merge that into a new object.  Save it to disc, then in a brand new hip file load it (with a clamp on the frame range) and do your CHOP thing, save out and load in the original scene.
>>
>> Sean
>>
>> On 2017-11-22 5:04 AM, Jordi Bares wrote:
>>> I may be shooting from the hip but, may be the approach should be that of a high frequency noise reduction taking in account the level of detail? A Laplacian based smooth could do the job (in a direct able way as well) without having to resort to the cloth transformation which I would bet won’t work for the reasons you state.
>>>
>>> My 2 cents
>>>
>>> jb
>>>
>>>
>>>> On 22 Nov 2017, at 09:39, Jerome Pastorello <lordkarington0 at gmail.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>>
>>>> I have a very strange problem of CHOP.
>>>> I did some quite heavy cloth simulation that I wanted to stabilize in my scene, jI just compensated the general movement and keep the cloth at the center of the scene by using a simple bound sop and inverting transform the cloth position to the center of its bounding box.
>>>>
>>>> Then I wanted to smooth the movement of this point Position (une point only, so 3 channels) because the cloth BB is changing pretty strongly through time.
>>>>
>>>> When I import the point with a geometry chop in chops I get an invalid source error, I thought it was coming from the file cache sop so I tried to copy some regular point on it, it kind of worked once, but now it is just calculating a « read back > loading geometry » for ages then I get the error again.
>>>>
>>>> I am quite stuck on this with a validated by the client scene. Doesn’t seem to be a logical behaviour at all.
>>>>
>>>> Is there any other way to smooth the animation of a point without going to CHOP ?
>>>> Is there a specific limitation to chops import ?
>>>>
>>>> Many thanx.
>>>>
>>>> Jérôme
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>> -- 
>>
>> Sean Lewkiw
>> CG Supervisor
>>
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