[Sidefx-houdini-list] VOPSOP by ID

Nicolas Delbecq nico.delbecq at gmail.com
Fri Nov 30 10:09:16 EST 2012


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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