[Sidefx-houdini-list] different forces on different wires

Andy Nicholas andy at andynicholas.com
Wed Jun 1 10:06:00 EDT 2016


One other idea that might possibly be simpler… just delete the hairs when they get detached. Each time a segment gets detached, save it out to a file called something like detached_hair.$F.bgeo. Then do a completely new wire simulation and use those files as the source. Just need to set the activation parameter of your wire object to match the current frame whenever the contents of detached_hair.$F.bgeo is not empty.


> On 1 Jun 2016, at 09:20, Gerbrand Nel <g at cannonballbunny.com> wrote:
> 
> Hey Todd
> Thanks for looking
> I looked at the scene and nothing seems to be happening.
> What do you mean by "force point attributes" ?
> Sorry, I feel like I'm being such a noob on this, but the solution is just out of my reach :P
> G
> On 31/05/2016 18:41, Todd Akita wrote:
>> Well this will solve the grouping (grouping based on whether a point in the prim has gluetoanimation).
>> 
>> You'll probably will need to use the force point attributes to drive the wiresolve...
>> 
>> -T
>> 
>> On Tue, May 31, 2016 at 12:01 PM, Gerbrand Nel <g at cannonballbunny.com <mailto:g at cannonballbunny.com>> wrote:
>> 
>>    Thanks Todd
>>    I must be missing something.
>>    Thanks for looking.
>>    G
>> 
>>    On 31/05/2016 17:45, Todd Akita wrote:
>> 
>>        Gerbrand -
>> 
>>        To clarify, you could attribpromote from point to prim (as
>>        maximum), or use
>>        a prim() expression in a popgroup node or the popwind force
>>        itself.
>> 
>>        Or you could also attribpromote it back from prim to point and
>>        then do
>>        something with that attribute...
>> 
>>        but sure I could look at it.
>> 
>>        -T
>> 
>>        On Tue, May 31, 2016 at 10:46 AM, Todd Akita
>>        <theakita at gmail.com <mailto:theakita at gmail.com>> wrote:
>> 
>>            Gerbrand -
>> 
>>            If you have a point attribute on the hair such as
>>            "gluetoanimation" you
>>            can just attribpromote that to prim and use that to set
>>            your grouping.
>> 
>>            -T
>> 
>>            On Tue, May 31, 2016 at 10:11 AM, Gerbrand Nel
>>            <g at cannonballbunny.com <mailto:g at cannonballbunny.com>>
>>            wrote:
>> 
>>                Hey Matt
>>                Long time :)
>>                Thanks for the suggestion!
>>                Problem is that our hair is in wind before the cut.
>>                Is there no way to set groups and only affect the
>>                grouped wires?
>>                I miss my state machines from soft right now :
>>                G
>> 
>>                On 31/05/2016 16:04, Matthew Kearney wrote:
>> 
>>                    Hey Gerbrand,
>>                    One possible approach would be to set the density
>>                    attribute on the 'cut'
>>                    wires to a ridiculously low value and have a wind
>>                    force that is light
>>                    enough that it doesn't affect the other hairs.
>> 
>>                    This worked a while back on a somewhat similar
>>                    setup, but it did take a
>>                    bit
>>                    of fiddling to find the right balance between the
>>                    wind and densities of
>>                    the
>>                    wires.
>>                    I also increased the kangular and klinear values a
>>                    lot to balance the
>>                    loss
>>                    of density.
>> 
>>                    it was a quick hack but did the job - hope it helps!
>>                    Matt.
>> 
>>                    On 31 May 2016 at 15:36, Gerbrand Nel
>>                    <g at cannonballbunny.com
>>                    <mailto:g at cannonballbunny.com>> wrote:
>> 
>>                    Hey guys
>> 
>>                        We have to create a scene where hair gets cut
>>                        by flying objects
>>                        I've managed to detach the hair by using a sop
>>                        solver.
>>                        Inside the sop-solver I just do a attribute
>>                        transfer to set the
>>                        attribute
>>                        "gluetoanimation" from 1 to 0.
>>                        This works well, but I now need to apply a
>>                        wind force to only the
>>                        severed
>>                        hair.
>>                        How would I do this?
>>                        It feels like it should be easy, but we can't
>>                        figure it out
>>                        Please help my dumb-ass :)
>>                        G
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