[Sidefx-houdini-list] Emitter velocity

Andy Nicholas andy at andynicholas.com
Thu Oct 25 09:26:44 EDT 2007


Thanks for your help guys. Got it sorted :-)

A

> Use a trail SOP to compute the velocity of the source/emitter geometry,
> and then set the source POP to "use inherited velocity" or "add to
> inherited velocity."  The global variables $VX,$VY,$VZ, or the point()
> expression can be used to access velocity elsewhere.  You can also
> calculate the magnitude (speed) of the velocity vector using
> length($VX,$VY,$VZ).  CHOPs can be used to calculate change in
> acceleration, etc.
>
> -Erik
>
>
> A ndras Ikladi wrote:
>> Hi Andy,
>>
>> The simplest I can think of is a trailSOP then using point() sample a
>> given
>> point's velocity attribute.
>> Alternatively feed the transform to CHOPs and derive the speed there..
>> but then you need to take both rotation and translation into account.
>>
>> cheers,
>> Andras
>>
>> ps: say hi to the guys at Axis, if you happen to head that way :)
>>
>> On 10/23/07, Andy Nicholas <andy at andynicholas.com> wrote:
>>
>>> Hi,
>>>
>>> Can anyone tell me how I can get the velocity of an object into an
>>> expression? I need to vary the direction of emission of some particles
>>> based on their emitter's velocity.
>>>
>>> I'm sure there's a simple answer, but I haven't found it yet!
>>>
>>> Thanks
>>>
>>> Andy
>>>
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>
>
> --
> erik zimmermann
> effects artist
> digital domain
> 300 rose avenue
> venice, ca 90291
> 310.314.2800 x2369
>
>





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