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Cloth Sim-- interactivity with other solvers?


Justin K

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Hey all, 
Pretty serious question from me here. Ive been trying to work on a scene including cloth over the last two weeks, and have come to the conclusion that the cloth solver does not play  with other solvers. It does not  support mutual affecting relationships as far as I can tell, unless the second object is another cloth object–which kind of defeats the purpose in certain situations. 

Am I correct about this? 

Basically I want to hit a piece of cloth with a bunch of RBD objects (very small ones), and send convincing cloth like currents through the surface (not sine wave based like it would be with the ripple solver). The objects have to respond to the cloth though, and bounce or split off the cloth. Im Basically simulating the effect of hail or large rain drops interacting with the cloth.


I have tried two main approaches. 
1) static objects based off of particles sims. I got some help off of the forums to trick the static object into seeing the same number of prims each frame so it didnt error out (http://www.toadstorm.com/blog/?p=307) thanks tanto!, but overall, this solution fails because the static objects dont interact with the cloth mutually, the static objects just pass right through and so the cloth literally snaps back into place after the object passes through. 


After this didnt work I understood that I needed a mutually affecting object relationship here. 
So I turned to RBD objects. 

Got some more help on this so I could still emit from particles first hand (https://lesterbanks.com/2016/08/easily-turn-houdini-particles-to-bullet-rigid-bodies/ [lesterbanks.com] ). However, the cloth simply will not interact with the bullet objects. I read somewhere to use the RBD solver instead and bypass the packed objects aspect, but when I did this, even with collision type set to volume, the pieces just fell through the cloth. 


I saw an old post this where it was asked why the cloth solver didnt play with the others, but that was in Houdini 14. Has this not changed, or am I missing something? 

If anyone can shed some light on this issue id appreciate it! 

Today Im switching to the bullet solver using grains (seems to be what all the cool kids are doing anyway – this is my main resource https://vimeo.com/219204848). Im just at a point now where Id like some clarification on this. 

The down side to going the grain method is I have less control over the cloth object behavior –johnny farmfield mentioned casually that it works great as a replacement for cloth, provided your working with silk like cloth. Thatbeing said, I will be getting a serious speed boost which will be helpful. 

Overall Im just looking for some clarification on this (Im more than happy to be proved completely wrong here . 


Thanks in advance! Ive attached a scene file if that would be of any use.   

CLOTH_&_RAIN_UPL (1).hiplc

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