[Sidefx-houdini-list] VOPSOP by ID

Nick Nimble nick at nicknimble.com
Fri Nov 30 10:15:39 EST 2012


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>
>>>>>      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>>
>>>>>>
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