[Sidefx-houdini-list] VOPSOP by ID

Nick Nimble nick at nicknimble.com
Fri Nov 30 10:01:54 EST 2012


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