ntkirby 5 Posted September 17, 2017 Hello everyone... I have a problem with an RBD packed object inheriting velocity. In the file, I have the attribute active being set by another object, but the velocity doesn't kick in at all. The velocity works if I remove the point wrangle setting active to 0 and remove the sop solver. If I try a pop vop or a geo vop, there's some weird velocity behavior that happens. If I tick on override attribute, the velocity takes off big time and doesn't appear that gravity takes hold. All I'm looking for is initial velocity once the pieces become active. I saw a few threads on the side fx forums and this forum, but nothing I saw seems to be working. Any thoughts? test_active_velocity.hipnc Share this post Link to post Share on other sites
Dam 9 Posted September 18, 2017 (edited) Hello Neil, Unfortunately something changes in the latest houdini versions about the inherit velocity from pack objects, a working way for inject the velocity only at the activation frame it's creating an attribute containing the previous @active value ($F-1), and add that to the "override attr from sop" inside the rbdpackedobject. That field should contain (@active and the created attribute containing the previous activation value ---> @prev_active) then with a geometry wrangle or pop wrangle it's possivle comparing the two attributes and gather the velocity to inject only if those two attribute are not the same with a point expression. I'm interested however if there are other ways for doing that, somebody have any idea? --Cheers Dam Edited September 18, 2017 by Dam Share this post Link to post Share on other sites
Varishtraheja 0 Posted September 18, 2017 Hey I do not know if this is what you wanted but its still a cool tip. test_active_velocity_v002.hipnc Share this post Link to post Share on other sites
ntkirby 5 Posted September 18, 2017 @Dam: When I was looking at the spreadsheet in the DOP network, I noticed using the active attribute that the velocity was being reset as opposed to when I didn't explicitly define that attribute and using the sop solver... @Varishtraheja: Not what I wanted. The animation needs to break apart like it's being affected by wind. Look at this: Share this post Link to post Share on other sites
julian johnson 74 Posted September 18, 2017 Not sure I've understood your scene so take this with a pinch of salt. But, it looks like you're trying to transfer both the velocity attribute and the active attribute of the active object to the inactive ones. To do that I calculated the velocity on the active object using Trail SOP and then in the attribute transfer in the solver also transferred the velocity. Probably not what you meant! test_active_velocity3.hipnc Share this post Link to post Share on other sites
ntkirby 5 Posted September 18, 2017 (edited) @julian johnson I looked at the file, it wasn't what I was looking for....for whatever reason, it's not keeping the initial velocity on the pieces when they are inactive. I want the velocity to take off as the objects become active. It doesn't matter whether I inherit velocity or even use the velocity on the rbd packed object to do it, it just won't do what I want. Edited September 18, 2017 by ntkirby Share this post Link to post Share on other sites
julian johnson 74 Posted September 19, 2017 Ah. OK, I think I now see what you mean. Matt Estela's done a great example of what I think you mean here: http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops#RBD_inherit_.40v_and_.40w_after_initial_frame I had a go on my own, too, and this seems to work as well. test_active_velocity4.hipnc Share this post Link to post Share on other sites
ntkirby 5 Posted September 19, 2017 @julian johnson - I saw the post here so I decided to try it. It worked, so I went ahead and tried some other things outside of using wrangles to see what I could accomplish and I get some odd results. I'll take a look at his H16 file and see if anything else is going on...I'll check yours too when I get home. Share this post Link to post Share on other sites
cwhite 60 Posted September 19, 2017 For animated static objects you shouldn't need to do any extra work to transfer velocity: https://www.sidefx.com/changelog/?journal=&categories=&body=inherit+velocity&version=16.0.491&build_0=&build_1=&show_versions=on&items_per_page=1 Share this post Link to post Share on other sites
ntkirby 5 Posted September 19, 2017 @cwhite I'm using 16.0.608 am I missing something though in my setup? The active attribute starts at 0 and at some frame later changes to 1, but the velocity doesn't transfer. Share this post Link to post Share on other sites
cwhite 60 Posted September 19, 2017 I think the object would also need to be marked as animated for the solver to fetch the updated value from SOPs Share this post Link to post Share on other sites
ntkirby 5 Posted September 20, 2017 @cwhite - Thanks for the help, I tried to set the animated value but it didn't work out. The solutions mentioned above worked out. Share this post Link to post Share on other sites
julian johnson 74 Posted September 20, 2017 That's a great new feature. Far less elaborate than before. So, now as long as you set the initial state to active 0 and animated 1, you can switch to active at any time, turn off animated via attribute transfer in SOPS and the objects will inherit velocity at any frame. test_active_velocity5.hipnc 2 Share this post Link to post Share on other sites
ntkirby 5 Posted September 20, 2017 Wow, ok... so I just learned something new again I apologize to @cwhite I just need to be properly educated Thanks again @julian johnson Share this post Link to post Share on other sites
dyei nightmare 3 Posted February 13, 2018 On 20/9/2017 at 7:07 AM, julian johnson said: That's a great new feature. Far less elaborate than before. So, now as long as you set the initial state to active 0 and animated 1, you can switch to active at any time, turn off animated via attribute transfer in SOPS and the objects will inherit velocity at any frame. test_active_velocity5.hipnc thats an elegant solution Share this post Link to post Share on other sites