[Sidefx-houdini-list] Grabbing velocity from dops

Louis Dunlevy ld at dneg.com
Fri Jun 29 05:15:22 EDT 2007


It's angvel.

Actually, it's quite annoying trying to compute vel and angvel in dops. 
There are lots of ways to set the Position data in DOPs using cool 
tricks (custom data, hacking existing assets as well as RBDState, 
Motion  etc etc) but no easy way of deriving the vel and angvel data 
from the result without having to make some custom data to do it.

It would be good if there was a flag somewhere in DOPs to output point 
velocity too.

xx
Louis

Ben Schrijvers wrote:
> But that vel attribute is only translation. I geuss when the objects 
> rotate you'll also have to use rotation velocity (rotvel?).
> That would then only work when you use the channels in object space. 
> So a geo node per object.. or some sort of instancing trickyness.
>
> cheers,
> benS
>
> Rangi Sutton wrote:
>> Louis Dunlevy wrote:
>>> the dopfield expressions should do it for you although obviously 
>>> you're only going to get the velocity of each individual piece 
>>> rather than a varying attribute over the surface. I've been lazily 
>>> putting a trail SOP down..
>>>
>>> dopfield("../dopnet1", "myRbdObj_$CUSTOMID", "Position", "Options", 
>>> 0, "vx")
>>> or maybe
>>> dopfield("../dopnet1", "myRbdObj_$CUSTOMID", "Position", "Options", 
>>> 0, "velx")
>>>
>>> or if you want to reference some custom data..
>>> dopfield("../dopnet1", "myRbdObj_$FUNNYID", "BirthData", "Options", 
>>> 0, "BirthFrame")
>>>
>>> I have noticed that DOPs transforms vector3 attributes so you could 
>>> try to pass v in and then suck it out and see what it looks like
>>>
>>> something along the lines of (although this is definitely wrong)
>>> dopfield("../dopnet1", "myRbdObj_$FUNNYID", "Geometry", "Options", 
>>> 0, "vx") +
>>
>> All good to know!
>>
>>
>>> Can you use the Dop Transform SOP in you're setup? That gives you 
>>> velocity.
>>
>> That's the head slap I was looking for!
>>
>>> beeeeeeeeer, or mybe milk.. hmm I'm not too gone on milk
>>
>> Bailies? Nah. Beers.
>>
>> r.
>>
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>
>
> _______________________________________________
> Sidefx-houdini-list mailing list
> Sidefx-houdini-list at sidefx.com
> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list




More information about the Sidefx-houdini-list mailing list