[Sidefx-houdini-list] water droplets running off the side of a bottle

Gerbrand Nel g at cannonballbunny.com
Thu Jan 21 04:49:03 EST 2016


Thanks everyone!!!
Thanks to you guys, my client is happy.
I never got to the double cross product, the bottle is standing upright, 
so a simple "move to centre in x and z" force made the drops stick to 
the bottle just fine :)

I started with the rain otl on orbolt, to get the trail spawning going.
I also spawned another trail with a life of 100 to generate a wetmap.
I used attribute transfer to extract the bottle geo around these 
particles, and used some noise displacements on these for the water trail.
The same wetmap particles had a pscale of 0, so I used another attribute 
transfer with a small radius, on the other droplets on the bottle, to 
fake the absorption of droplets as the main drop travelled down the bottle.

I didn't use the liquid surface sop, I couldn't figure out how to get it 
to look at pscale, so I used a copy sop with spheres, and a vdb from 
polygons to create the liquid surface.

The scene is a mess, but I will gladly share it if anyone needs to do 
something like this.
G


On 20/01/2016 21:46, Personal wrote:
> Great idea with cross product. Would never thought about that, I am so crap in math. But it works nice.
>
>
> -- 
> Micic Srecko
> -------------------
> Mail:
> srecko.micic at gmail.com
> Skype:srecko.micic
> -------------------
> On 19/01/2016 21:39:07, Olivier Jeannel <facialdeluxe at gmail.com> wrote:
> The double cross product can be copied from Softimage's "flow on surface".
> The principe is the same.
>
> If you want to use the SDF,inside Popvop you'll gather the distance from
> an SDF surface using a Volume_Sample (if the value is negative the particle
> is inside, if it is positive the particle is outside, and if it returns
> zero you're on the surface)
> You sample the direction (equivalent to the Normal but for an SDF) using a
> Volume_Gradient.
>
> Just be focused, and respect the cross product order and normalize
> everything.
> You'll end up with a plate of spagehties, but it works.
>
> On Tue, Jan 19, 2016 at 7:16 PM, Gerbrand Nel wrote:
>
>> Thanks everyone!!
>> I shall try
>> found this one too:
>> https://vimeo.com/40954039
>> Bit over the top for my 1 day budget, but there are some nice ideas in
>> there.
>> G
>>
>> On 19/01/2016 19:49, Javier Meroño wrote:
>>
>>> if you want a reusable tool for dripping droplets like this one
>>> https://vimeo.com/artkill/dropletsrnd
>>>
>>>
>>> then Olivier is right on the money, you need to force the particle
>>> trajectory with a POPVOP using a double cross product and afterwards use
>>> VDB volumes so that the droplets merge together properly . It´s not an
>>> obvious tool to create, though, and it will take some research and
>>> development on your side, so be sure it´s something you will reuse before
>>> going into it.
>>> Javier Meroño
>>>
>>>> From: parker.jon at gmail.com
>>>> Date: Tue, 19 Jan 2016 12:03:42 -0500
>>>> To: sidefx-houdini-list at sidefx.com
>>>> Subject: Re: [Sidefx-houdini-list] water droplets running off the side
>>>> of a bottle
>>>>
>>>> How about scattering some points around your surface, then scatter a
>>>> separate group near the bottom of your object and use the
>>>> findShortestPath node to draw lines that connect them. The lines
>>>> should follow the contours of your object in a fairly realistic way
>>>> and you can then just animate the droplets to follow the curve paths,
>>>> no simulation needed.
>>>>
>>>> Jon
>>>>
>>>> On Tue, Jan 19, 2016 at 10:46 AM, Ron Schab wrote:
>>>>
>>>>> jep particles or u can have a look at this thing here:
>>>>>
>>>>> https://www.orbolt.com/asset/SideFX::vfx_rain
>>>>>
>>>>>
>>>>> SideFx-made HDA that going of the description should offer what u are
>>>>> after. Haven't downloaded and tested, just remembered seeing it a while
>>>>> ago.
>>>>>
>>>>> At least should give u some ideas - it's free too
>>>>>
>>>>> good luck.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Tue, Jan 19, 2016 at 4:25 PM, Olivier Jeannel
>>>>> facialdeluxe at gmail.com>
>>>>> wrote:
>>>>>
>>>>> Double cross product is the way to get some slide on surface based on
>>>>>> incoming velocity.
>>>>>> But there might be a pop doing that, already.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Tue, Jan 19, 2016 at 3:52 PM, Srecko Micic
>>>>>> wrote:
>>>>>>
>>>>>> And for moving particles, I did once similar with particle collision
>>>>>>> POP,
>>>>>>> and Respond set to slide. But not sure will that work in your case.
>>>>>>> --
>>>>>>> Srecko Micic
>>>>>>> 3D Generalist
>>>>>>> -------------------------------------------
>>>>>>> Skype: srecko.micic
>>>>>>> Email: srecko.micic at gmail.com
>>>>>>>
>>>>>>> On Jan 19, 2016, at 3:04 PM, Srecko Micic
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Try to scatter particles on surface. And than use Particle Fluid
>>>>>>>>
>>>>>>> Surface
>>>>>>> to mesh them, for example?
>>>>>>>
>>>>>>>> --
>>>>>>>> Srecko Micic
>>>>>>>> 3D Generalist
>>>>>>>> -------------------------------------------
>>>>>>>> Skype: srecko.micic
>>>>>>>> Email: srecko.micic at gmail.com
>>>>>>>> http://sreckom.webworkman.com
>>>>>>>>
>>>>>>>>> On Jan 19, 2016, at 2:21 PM, Gerbrand Nel <>
>>>>>>>>>
>>>>>>>>> wrote:
>>>>>>>> Hey guys
>>>>>>>>> This one client called me and needs photo real droplets on a bottle
>>>>>>>>> by
>>>>>>>>>
>>>>>>>> the end of tomorrow.
>>>>>>>> I've done this in softimage in the past, but I was wondering if
>>>>>>>>> anyone
>>>>>>>>>
>>>>>>>> knows of a nice tutorial or demo file of this in houdini?
>>>>>>>> The static droplets is not the problem,
>>>>>>>>> I'm looking for some ideas on how to create the run-offs, how they
>>>>>>>>>
>>>>>>>> pick
>>>>>>> other droplets up on the way, and leave a trail behind.
>>>>>>>
>>>>>>>> Thanks guys
>>>>>>>>> G
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