[Sidefx-houdini-list] VOPSOP by ID

Nick Nimble nick at nicknimble.com
Fri Nov 30 10:31:25 EST 2012


I tested this with a .bgeo particle cache, a file feeding into a 
timeblend and then a timewarp node. Depending on the scale of your warp 
you can add a timeshift node to jump in time to the point that is most 
interesting.

@Szymon, yes that is true. How ever if it comes at a massive cost, then 
I think I'll settle for this option. For me the Python Sop path seemed 
the most doable (I have zero C++ experience), but these always come at a 
cost and don't scale well. I want to apply this on millions and millions 
of particles.

Cheers,
Nick, be Nimble
+31 622 4243 94 | www.nicknimble.com | www.facebook.com/nicknimble

On 11/30/12 4:21 PM, Szymon Kapeniak wrote:
> I've thought the challenge was to not to make it linear...
>
>
> 2012/11/30 Nick Nimble <nick at nicknimble.com>
>
>> Hi Nico!
>>
>> Gha, what a joke! It works flawlessly. Thank you very much my friend :-)
>> Lucky Mark E. was fooled by the challenge as well, which in turn makes me
>> feel less stupid ;-).
>>
>>
>> Cheers,
>> Nick, be Nimble
>> +31 622 4243 94 | www.nicknimble.com | www.facebook.com/nicknimble
>>
>> On 11/30/12 4:09 PM, Nicolas Delbecq wrote:
>>
>>> Maybe I'm missing the point here but can't you just use the timeblend sop
>>> ?
>>> If an id attribute is present it will use that instead of the pointnumber
>>> to interpolate the positions...
>>>
>>> On Fri, Nov 30, 2012 at 3:01 PM, Nick Nimble <nick at nicknimble.com> wrote:
>>>
>>>   Hi Mark,
>>>> Tnx for your input.
>>>>
>>>> I like your thinking! How ever I have zero experience with writing vex
>>>> code. I've tried using the inline vop, but I can't get it to work. I have
>>>> two inputs in my inline vop: id (int)  and pointCloudFile (string) and an
>>>> Output name: handleOut handle
>>>>
>>>> Code:
>>>> string pcf = $pointCloudFile;
>>>> int idIn = $id;
>>>> int handle = pcopen(pcf, id, int idIn, float 2, int 1);
>>>> $handleOut = handle;
>>>>
>>>> The problem is, is that I don't know if my unknowingness is the problem
>>>> or
>>>> that our little trick doesn't work in the first place.
>>>>
>>>>
>>>> Cheers,
>>>> Nick, be Nimble
>>>> +31 622 4243 94 | www.nicknimble.com | www.facebook.com/nicknimble
>>>>
>>>> On 11/30/12 1:54 PM, Mark Elendt wrote:
>>>>
>>>>   Hi Nick,
>>>>> I don't know if this would work or not, but could you build a point
>>>>> cloud based on id's?  You don't have to organize point clouds in
>>>>> space, you can use any "space" you want (i.e. color or ID).  So, using
>>>>> an id point cloud would let you look up the attributes based on id...
>>>>>
>>>>> If this works (and I don't know 100% if it will), feel free to post
>>>>> the answer on the list.
>>>>>
>>>>> Cheers,
>>>>>
>>>>>
>>>>> On Friday Nov 30 at 13:14, Nick Nimble wrote:
>>>>>
>>>>>   Yes,
>>>>>> I want to retime or slow them down. I would like to beable to blend
>>>>>> between
>>>>>> 2 frames. Initially I would like to not only linearly blend between the
>>>>>> points but also use to velocity to introduce some curvature. This will
>>>>>> only
>>>>>> be visible in very extreme situations, but I want it to visually work
>>>>>> on
>>>>>> a
>>>>>> macro level.
>>>>>>
>>>>>> The goal is to retime 24FPS particels to say 1000FPS, like Discoveries
>>>>>> Timewarp.
>>>>>>
>>>>>> Cheers,
>>>>>> Nick, be Nimble
>>>>>> +31 622 4243 94 | www.nicknimble.com | www.facebook.com/nicknimble
>>>>>>
>>>>>> On 11/30/12 12:57 PM, Alvin Yap wrote:
>>>>>>
>>>>>>   For each particle, you need to connect it to the next (future) frame?
>>>>>>> If
>>>>>>> you only need a linear blend, you could store the current velocity
>>>>>>> value
>>>>>>> and then you should know the next position in time at the current
>>>>>>> frame
>>>>>>> yes?
>>>>>>>
>>>>>>> Alvin
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Nov 30, 2012 at 11:50 AM, Nick Nimble <nick at nicknimble.com
>>>>>>> <mailto:nick at nicknimble.com>> wrote:
>>>>>>>
>>>>>>>       Hi Alvin,
>>>>>>>
>>>>>>>       How would you do that? Besides I also want to be able to look
>>>>>>>       ahead of time.
>>>>>>>
>>>>>>>       In its simplest form I want to use a timeshift node connected to
>>>>>>>       the second and one to the third input of a VOPSOP and import an
>>>>>>>       attribute by $ID instead of PT.
>>>>>>>
>>>>>>>       Cheers,
>>>>>>>       Nick, be Nimble
>>>>>>>       +31 622 4243 94  <tel:%2B31%20622%204243%2094>  |
>>>>>>> www.nicknimble.com <
>>>>>>> http://www.nicknimble.com>  |www.facebook.com/nicknimble  <
>>>>>>> http://www.facebook.com/****nicknimble<http://www.facebook.com/**nicknimble>
>>>>>>> <http://www.**facebook.com/nicknimble<http://www.facebook.com/nicknimble>
>>>>>>>       On 11/30/12 12:44 PM, Alvin Yap wrote:
>>>>>>>
>>>>>>>        How about storing the previous frames' data as attributes on
>>>>>>>> each
>>>>>>>>       particle?
>>>>>>>>
>>>>>>>>       Alvin
>>>>>>>>
>>>>>>>>
>>>>>>>>       On Fri, Nov 30, 2012 at 11:22 AM, Nick Nimble
>>>>>>>>       <nick at nicknimble.com <mailto:nick at nicknimble.com>> wrote:
>>>>>>>>
>>>>>>>>           Hi!
>>>>>>>>
>>>>>>>>           I'm working on a method to re-time aka interpolate
>>>>>>>> particles.
>>>>>>>>           I would like to use a vopsop and do this as a post process.
>>>>>>>>           The idea is to use the point position of the neighboring
>>>>>>>>           frames and their velocities to calculate an in-between
>>>>>>>> position.
>>>>>>>>
>>>>>>>>           The problem is, a vopsop works by point numbers and not
>>>>>>>>           particles ID's and since point-numbers change when a
>>>>>>>> particle
>>>>>>>>           dies...
>>>>>>>>
>>>>>>>>           Any suggestions? I was thinking about the sort SOP, or
>>>>>>>>           something like that. A method to match the point number by
>>>>>>>>           the particle ID. Still this would result in missing
>>>>>>>>           point-numbers and I'm not sure if Houdini would like that.
>>>>>>>>
>>>>>>>>           --         Cheers,
>>>>>>>>           Nick, be Nimble
>>>>>>>>           +31 622 4243 94 <tel:%2B31%20622%204243%2094> |
>>>>>>>>           www.nicknimble.com <http://www.nicknimble.com> |
>>>>>>>>           www.facebook.com/nicknimble <http://www.facebook.com/**
>>>>>>>> nicknimble <http://www.facebook.com/**nicknimble<http://www.facebook.com/nicknimble>
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