[Sidefx-houdini-list] VOPSOP by ID

Alvin Yap alvinyapvfx at gmail.com
Fri Nov 30 07:36:56 EST 2012


Eeep, I missed your need to retime, I read it as more of interpolating
between frames. I think this storing velocity could work for your retime
needs. The velocity storing will allow a linear blend between current frame
and next frame, so I think (offhand, not tested) it will be a matter of
mapping the frames and then intepolating.

Getting curvature is not fun, I think we had some guys use some tricks with
the trail sop to get curves for that, if not you will need to try stuff
like storing the position of the particle for two frames back and one frame
forward together with a catmult rom curve for that. I think it's do-able,
if annoying.


On Fri, Nov 30, 2012 at 12:14 PM, Nick Nimble <nick at nicknimble.com> 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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>>
>>
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