forces in Dops

[mirHadi]

hello

 

the doc says: "You should not use the Wind Force DOP or any of the other forces in DOPs because they will generate inferior results compared with the Air Drag model."

is it true for wire and cloth simulations or it is a general suggestion?

 

what should be used instead to influence a cloth?  

I need wind force... or other forces ( like a normal way I do regularly  in Maya).

 

please help understand this... 

thank you very much.

[anim]

it used to be true for cloth and wire
however since H14 a few other DOP forces were updated to support cloth drag model

 

Friday, January 30, 2015
Houdini 14.0.230: Fixed support for all remaining DOP forces in the finite element solver (Fan, Uniform, Wind noise). Still, the use of the Fan Force is not recommended with the Solid Object or the Cloth Object; use the Wind Force instead of the Fan Force whenever you can. A separate rewrite of the Fan Force is still needed.

Edited October 25, 2015 by anim

[mirHadi]

thank you Tomas!

 

interesting, I missed that part of information!.

I think It would've been very strange not being able to use forces with cloth and wire before!!

 

in H 15, there is no major upgrade for forces for cloth and wire, think not using Fan Force still persists. I like Wind force though!.

[anim]

the problem was not that it wouldn't work with those forces before, but that it didn't use advanced drag model (normal/tangent drag) for cloth/wire, therefore you would get less realistic motion, or not realistic at all

(I haven't tried since DOP forces were updated, but if I remember correctly that was supposed to be the update)

 

the workaround before was to use External Velocity Field and External Velocity Offset for your wind, which you can still use, actually it was probably considered proper workflow, but to me it always seemed so isolated and tedious that it have felt as workaround

I wish cloth/wire/fem was as well updated to work with POP wind forces, but for that they would first need to free up targetv as that is currently used for other purpose than the one in POPs

[mirHadi]

Tomas! 

I'm trying to avoid using fexternal and force attribute.

for a jellyfish like creature I want to to make the creature orient itself toward the movement direction.

 

I saw a tutorials about it, like using sop solver to fetch the original ( non animated )geometry and with another dop import ( inside sop solver ) to fetch the animated geometry to calculate the velocity vector direction at each frame. and then use something like fexternal attribute to force creature move forward as It moves through noisy space and maintains its orientation to the path.

 

but It seems unpredictable and need to be something more practical.

with your explanation I understand that I need to use targetv or target to make it work. unfortunate I don't know how!! 

[mirHadi]

in H 15, wire solver doesn't take the fexternal into account. 

 

I want to orient object towards its moving direction and fexternal was a good option. I don't know how to take custom forces fed into wire solver.

is there a way around this?

 

thank you in advance

 

Ps:  I got an aswer from sesi, in case it may help others:

Support for "fexternal" was removed in Houdini 14 as it was incompatible with other improvements. Please use a "force" attribute on the Geometry sub-data instead.

Edited December 7, 2015 by haaranoos